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Guide II MSO-447 - History

Guide II MSO-447 - History



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Guide II

(MSO-447: dp. 665, 1. 173'; b. 35'; dr. 11'; s. 12 k.; cpl. 75; a. 1 40mm.; cl. Agile)

The second Guide (MSO 447) was launched 17 April 1954 by the Seattle Shipbuilding & Drydocking Corp., Seattle, Wash.; sponsored by Miss Ann L. Larson; and commissioned 15 March 1955, Lt. John Eh Lowell in command. Her hull classification changed from AM-447 to Am 447 on 7 February 1955.

Guido spent the first year of her career in coastwise operations off California. This duty included surveys for the Navy Hydrographic Office in the San Diego-Long Beach area and in San Franeisco Bay approaches. She departed Long Beach 1 October 1956 and arrived in Yokosuka 31 October for minesweeping exercises that took her off the coast of Korea, thc Mnrinnas Islands, and along the coast of Japan. She returned to Long Beach 15 April for 2 years of training along the western seaboard. On 2 April 1959 she again deployed for the Far East, expanding duties to include joint mine exercises with the naval forces oi Japan, Korea and Nationalist China.

Guide returned to Long Beach from her second Asian tour 15 October 1959 and resumed operations along the Oalifornia seaboard for the next 2 years. On 1 May 1961 she sailed on her third tour of duty with the 7th Fleet, arriving in Yokosuka, Japan, 29 May 1961. Following amphibious and other mine warfare exercises to the coasts of Korea and the Philippines, she returned to Long Beach 14 November. The next 16 months were filled with mine countermeasure and minesweeping training that took her as far north as Seattle and Esquimalt, British Oolumbia.

Guide was again underway for the Far East 5 April 1963, touching Midway and the Marianas on her way to Japan. She again swept to the shores of Taiwan, Korea, and the Philippines before returning to Long Beach 5 November 1963. Coastwise training occupied her until 5 April 1965 when she sailed for Guam, Marianas Islands, arriving 3 May 1965.

Guide underwent a 3-week upkeep period at Guam. She arrived off the coast of Vietnam 1 June to begin the first of three periods of "Market Time" anti-infiltration patrols to deny movement of war supplies to the Viet Cong. Her first patrol terminated 31 June. Subsequent patrols were carried out 25 July-12 August 1965 and 18 September5 October 1965. Following a liberty call ut Hong Kong she paid a 2-day visit to Iloilo City, Panay, Repu~blic of the Philippines. She opened for general visiting 2~28 October and contributed books and food to assist in America's people-to-people program of international friendship.

Guide joined in combined mine warfare exercises with units of the Philippine Navy before setting course for the Marshalls, Hawaii, and back to Long Beach, arriving 14 December 1965. The minesweeper operated along the West Coast throughout 1966 and sailed for the Far Fast early in 1967. On 1 March she was off the coast of Vietnam laboring to keep clear the shipping lanes which supply Allied fighters in that war-torn land. She continued to perform this vital duty past mid-year, reaffirming her right to the proud name Guide.


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Beaver Falls

The high plateau above the Beaver River, north of the Ohio River, was settled in the late 18th century. The town was called Brighton and later renamed Beaver Falls. The Harmony Society led an economic revival in the area in the mid-19th century. Beaver Falls was incorporated as a borough in 1869 and a city in 1928.

The first Jewish settler in Beaver Falls, Pa. was Charles Levi, a twenty-four-year-old baker who arrived in 1870. Max Solomon opened a scrapyard in Beaver Falls in the 1880s. At the time that these men and their families, and other families like them, were settling in Beaver Falls, the Jewish community of Beaver County was centered at a moderately Reform congregation in nearby New Brighton called Tree of Life. Some of the early Jewish families in Beaver Falls were likely Reform as well. In December 1871, twelve Jewish families from the Beaver Valley arranged for Rabbi Judah Wechsler of Columbus, Ohio, to come to New Brighton. His address at a local church drew a Jewish and non-Jewish audience, according to The Jewish Experience in Western Pennsylvania, A History: 1755-1945.

Tree of Life gradually dissolved after its leading member died in 1883. Over the next two decades, Beaver Falls became the larger of the two neighboring Jewish communities. A group of mostly Lithuanian immigrants chartered Agudath Achim Congregation of Beaver Falls on October 20, 1904, with nine members, Asher Hanauer, Max Solomon, Morris Gordon, William Pfeifky, Moses Solomon, Louis Wasbutzsky, Nathan Rosenberg, Simon Berkman and Louis Wilkofsky. That same year, a group of women associated with the congregation founded the Agudath Achim Sisterhood. Agudath Achim established a cemetery in White and Patterson Townships in 1906. Agudath Achim initially met at the Hanaur Theatre Building at the corner of 7th Avenue and 5th Street in Beaver Falls, according to a Works Progress Administration Church Archives survey. The Orthodox congregation built its first synagogue at 5th Avenue and 6th Street in 1914.

By the early 1920s, Beaver Falls and New Brighton essentially comprised a single Jewish community, which often referred to itself as the Beaver Valley. The Beaver Valley Section of the National Council of Jewish Women was founded in June 1917 with Nettie Silverman as its first president. Among the first projects of the organization was establishing the Beaver Valley Hebrew Religious School, which held its first confirmation ceremony in 1917.

The B’nai B’rith Lodge No. 777 was founded on June 12, 1921 with 35 members. The lodge met at rented rooms until 1947, when it purchased meeting space on 16th St. The lodge eventually oversaw several youth organizations in Beaver Falls, including the Beaver Valley A.Z.A. No. 117 in 1929 and the Beaver Valley B.B.G. in 1941. The Beaver Valley Zionist District was founded around the time of Agudath Achim Congregation, and perhaps earlier. It later became a chapter of the Zionist Organization of America. The Beaver Valley Chapter of Hadassah was founded on March 18, 1945. In 1947, a group of Agudath Achim members who had recently returned from military service in World War II formed a Men’s Club at the congregation. The group served a spiritual and educational mission, meeting after morning prayers for monthly study and conversation.

The Jewish population of Beaver Falls and New Brighton grew steady over the first half of the 20th century. A directory in the 1907-1908 edition of the American Jewish Yearbook listed 45 members associated with Agudath Achim. The yearbook listed a Jewish population of 121 for Beaver Falls in its 1918 edition, 300 for Beaver Falls and 95 for New Brighton in its 1928-1929 edition, 415 for Beaver Falls and 250 for New Brighton in its 1940-1941 edition and 813 for the combined “Beaver Valley” region in its 1951 edition.

The growth in population created communal opportunities. A new Reform congregation called Beth El was established as early as 1948. In early 1955, a Beaver Falls resident named Jacob Venger called a meeting for the purposes of creating a Jewish community center in Beaver Valley. The group acquired property in Chippewa Township in January 1957 and officially chartered the Beaver Valley United Jewish Community that December. The new Beaver Valley United Jewish Community Center was dedicated in May 1960. In addition to having meeting halls and classrooms, the new center was designed with two sanctuaries. Agudath Achim Congregation moved into the main sanctuary. Beth El decided not to affiliate with the center and later dissolved, but a second Reform congregation called Beth Sholom was created in 1960 and used the smaller sanctuary. The Beaver Valley United Jewish Community Center also became a centralized meeting place for Jews living outside of the Beaver Valley. After Tree of Life Congregation in nearby Rochester closed in 1973, many former members came to Beaver Falls.

The Jewish population of Beaver Valley began to contract in the 1980s. The American Jewish Yearbook listed a population of 350 for Beaver Falls and 500 for “Upper Beaver” in its 1984 edition and a population of 200 for “Upper Beaver County” in its 1992 edition. Beth Sholom disbanded in 1986. The three Jewish women’s organizations in the area were holding combined meetings as early as 1997. The Beaver Valley United Jewish Community Center merged with Beth Samuel Congregation in Ambridge in 2006.


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The Function of Inhibition in ILD Processing can Explain its Role in ITD Processing

ILDs as a Starting Point for a Population Code of Spatial Position

As outlined above, early mammals most probably could hear high-frequency sounds and had relatively small heads. Hence, ILDs were the only binaural cues available to them for azimuthal sound localization. This suggests that the ancestral neuronal structure used to process binaural spatial information was devoted to ILD detection. It is well established that ILD sensitivity is generated by the LSO in the brainstem, whose bipolar neurons are the initial site of binaural convergence (Galambos et al., 1959 Boudreau and Tsuchitani, 1968 Tsuchitani and Boudreau, 1969). They integrate excitatory (glutamatergic) inputs from the ipsilateral antero-ventral cochlear nucleus (AVCN) with inhibitory (glycinergic) inputs coming from the ipsilateral medial nucleus of the trapezoid body (MNTB), which itself is innervated by the contralateral AVCN (Figure 4). This integration process can be thought of as a comparative mechanism that gages the relative sound levels at the two ears (within a particular spectral bandwidth at a given time point), which are encoded in the respective activity levels of the two LSO inputs (Moore and Caspary, 1983 Finlayson and Caspary, 1989 Sanes, 1990 Tollin, 2003). Accordingly, LSO response rates (measured as the number of action potentials elicited per unit time) are highest for ipsilateral sound-source locations that create positive ILDs, i.e., high sound level at the ipsilateral ear allows the excitatory pathway to be fully activated, whereas the sound level at the farther ear is greatly attenuated by the skull, and thus activation of the contralateral inhibitory pathway is minimal. More importantly, response rates are faithfully modulated as a function of the ILD, and most LSO neurons are completely inhibited from spiking at ILDs favoring the contralateral ear (negative ILDs). Such ILD response functions typically take the shape of a sigmoid, generating high sensitivity for small changes in ILD along the slope of the function (Figure 4). Note that any ILD sensitivity found in downstream brain areas crucially depends on an LSO input, be it excitatory or inhibitory. This is most probably attributable to neuronal specialization necessary for ILD extraction (see below).

FIGURE 4. The coincidence mechanism of LSO neurons allows both as ILD and ITD detection. (A) LSO neurons receive excitatory inputs from SBCs in the ipsilateral AVCN and inhibitory inputs from the MNTB that is innervated from by GBCs from the contralateral AVCN. (B) The spatial tuning functions of LSO neurons take a hemispheric shape with the slope of the functions crossing frontal azimuthal positions. Upper and lower panels show normalized tuning functions for LSO neurons in cat with CFs below and above 10 kHz, respectively, recorded under virtual acoustic space stimulation that incorporates the HRTFs. Re-printed with permission from Tollin and Yin (2002). (C) Low CF neurons in the LSO are both ILD and ITD sensitive: upper panel shows ILD tuning function of a cat LSO neuron (CF = 566Hz), while the lower two panels illustrate the ITD-sensitivity of the same neuron. Note that the characteristic delay (CD) for this neuron, i.e., the delay of coincidence of excitatory and inhibitory inputs, results in a minimal response rate. Re-printed with permission from Tollin and Yin (2005).

The LSO has no homolog in other vertebrates. In birds, ILD sensitivity is generated by convergence of contralateral excitatory and ipsilateral inhibitory inputs at the level of the lateral lemniscus (Moiseff and Konishi, 1983 Takahashi and Keller, 1992). This connectivity therefore represents a rather complex reciprocal ILD processing circuit that does not reflect the integration mechanism of monaural inhibition and excitation of the mammalian LSO: first, inhibitory and excitatory ear are reversed. Second, the ipsilateral inhibition is conveyed by the lateral lemniscus of the other hemisphere, hence by a binaural nucleus. Third, because it is conveyed via an additional synaptic station through the binaural detector of the other hemisphere, inhibition is significantly delayed relative to excitation and seems to serve a response gain modulation (Steinberg et al., 2013). As we will explain in the following and in 3.2., inhibition in the LSO has purposes directly related to establishing binaural sensitivity.

The LSO is well-developed in all terrestrial mammals, including echo-locating bats and humans (Moore, 2000). The overall size of the LSO in a particular species seems to correlate with the range of frequencies to which that species is sensitive (Moore, 2000), most probably owing to the tonotopic organization of the nucleus. All mammals appear to use the same neural mechanism for processing ILDs in the LSO, namely the integration of ipsilateral excitatory inputs from the AVCN and contralateral, inhibitory inputs via the MNTB (see below, Grothe, 2000 Yin, 2002 reviewed in Grothe et al., 2010). Hence, they employ similar coding strategies for high-frequency sound-source localization at the level of the LSO. This coding strategy can be described as a roughly hemispheric code in which individual neurons encode a range of ILDs through response-rate modulation along the slope of their ILD functions (Tollin and Yin, 2002). The LSO neurons studied to date exhibit rather similar ranges of sensitivity to ILDs: the slope of LSO ILD functions is typically centered close to 0 dB ILD (Park et al., 1997, 2004 Park, 1998 Tollin and Yin, 2002). Interestingly, in a study of the cat LSO using virtual space stimuli (i.e., incorporating monaural spectral effects of sound-source location), Tollin and Yin (2002) observed that the tuning of LSO neurons is remarkably stereotypic, as the slope of most spatial-response functions covered a similar range of azimuthal space around the midline and the nearby ipsilateral areas (Figure 4). Together, these findings suggest an overrepresentation of near-midline locations, in agreement with the reported maximal psychophysical resolution of ILDs around the midline (Blauert, 1997). However, the interpretation of characteristics of ILD functions in general is difficult, as the peak and slope positions of ILD functions are markedly affected (shifted) by previous activity levels (Park et al., 2008). These shifts are mediated by, among other mechanisms, the retrograde release of GABA from LSO cells onto their own presynaptic inputs (Magnusson et al., 2008), which suggests high plasticity of ILD coding based on recent stimulus history. Hence, even at the level of single binaural comparator neurons, representations of spatial positions are likely to change according to the current auditory context rather than being inflexibly coded. This use of inhibition to generate flexible representations, and their implications for downstream coding, are discussed in more detail in Section 𠇍ynamics of ILD and ITD Processing: GABAB-Mediated Inhibition” below.

ILD Processing – The Role of the MNTB and Glycinergic Inhibition

The integration of inhibitory and excitatory inputs by LSO cells is often informally referred to as subtraction. This overly simplistic analogy should be treated with caution, insofar as it tends to imply the comparison of net activity levels in the ipsi- and contralateral input integrated over the entire duration of a given acoustic stimulus. In fact, essentially the opposite is true, as timing information – more specifically, information relating to temporal fluctuations in stimulus amplitude – is highly conserved within the LSO circuit. Indeed, neurons involved in ILD detection, including the components of the inhibitory MNTB pathway, are among the most temporally precise in the brain. Two key demands on the system impose the need for high temporal acuity.

The first is the general functional requirement for high temporal resolution in sound localization circuits. These systems cannot afford to integrate over long intervals to produce an average intensity difference, because the source of this average signal might well have changed in the meantime. Moreover, in the presence of multiple, concurrently active sound-sources, short integration times are crucial for discrimination between individual sounds (Meffin and Grothe, 2009 Khouri et al., 2011). Natural signals (communication calls, speech, rustling noises generated by moving prey, etc.) are characterized by prominent and rapid amplitude modulations. Hence, to faithfully detect and track the site of origin of such signals, the LSO circuit must be able to resolve ILDs on very short temporal scales (Joris and Yin, 1995 Tollin, 2003). This is accomplished by the well-known phenomenon of phase-locking, which describes the ability of auditory (brainstem) neurons to lock the timing of their spiking activity to a particular phase of the stimulus (Joris et al., 1994). Phase-locking is commonly invoked in the context of low-frequency carrier or envelope sinusoidal signals, but can (and should) be generalized to the encoding of the rising slopes or transients in any complex signal, irrespective of its frequency (Dietz et al., 2014). Accordingly, phase-locking allows for the precise encoding of a particular time of occurrence in the auditory nerve and downstream pathways. The classical work of Joris et al. (1994) has demonstrated that the quality of phase-locking (measured in terms of vector strength) is actually maintained or even enhanced in the post-synaptic target of the auditory nerve fibers of the binaural system, namely the spherical and globular bushy cells (SBCs and GBCs) of the AVCN, which provide the input to MNTB and LSO, respectively (Warr, 1966 Spangler et al., 1985 Cant and Casseday, 1986 Friauf and Ostwald, 1988 Sanes, 1990). In particular, synaptic transmission between GBC axon and MNTB soma has been studied extensively because of the large size of the pre-synaptic structure (Schneggenburger and Neher, 2005 Kopp-Scheinpflug et al., 2011 Borst and Soria van Hoeve, 2012), and this synaptic relay is one of the fastest and temporally most precise known in the brain (von Gersdorff and Borst, 2002). Evidently, MNTB neurons exhibit similar phase-locking precision to GBCs, while LSO cells – the post-synaptic targets of both MNTB and SBCs – themselves exhibit fast membrane kinetics that allow for exquisite temporal sensitivity to the arrival time and duration of incoming synaptic events (Tollin, 2003). Taken together, these properties of the LSO circuit allow for highly precise and independent ILD processing of each fast transient or onset in a signal.

The second functional demand that necessitates the extreme temporal sensitivity of the LSO circuit is directly linked to the previous argument and explains the specific morphological and physiological adaptations for temporal fidelity and transmission speed that are found within the inhibitory sub-circuit involving the MNTB. A faithful representation of amplitude-modulated signals requires not only that both the excitatory and inhibitory inputs should reliably encode the precise time of occurrence of transient events, but also that both inputs should arrive in close coincidence at the LSO cell to allow for interaction of the two. Clearly, this poses a challenge for the inhibitory input, as it must somehow compensate for the longer axonal pathway from the contralateral AVCN, as well as for the additional synapse between GBC and MNTB, which will introduce a further delay. Indeed, a detailed anatomical examination of the MNTB pathway reveals particular specializations for high conduction velocity, as both axon diameter and myelin thickness are larger in GBCs than in SBCs (Morest, 1968 Schwartz, 1992). Moreover, synaptic delays at the calyx of Held are among to the shortest that have been measured in the CNS (von Gersdorff and Borst, 2002 Kopp-Scheinpflug et al., 2011). Accordingly, physiological evidence shows that inhibition is capable of suppressing even the first spike of LSO responses (Tsuchitani, 1988 Tollin, 2003), demonstrating (at least) coincident arrival of contralateral inhibition and ipsilateral excitation.

In summary, the ILD circuit represents the ancestral binaural sound localization circuit of mammals. LSO neurons detect ILDs via a coincidence detector mechanism of ipsilateral excitation and contralateral inhibition. All components of the LSO circuit are tuned for temporal fidelity, and the inhibitory pathway of the MNTB in particular has evolved anatomical and physiological adaptations to compensate for the longer pathway and additional synaptic delay.

ITD Processing is Derived from ILD Processing in Mammals

Shared components of ILD and ITD circuits

The evolutionary and anatomical evidence suggests that, as a nucleus for highly precise binaural discrepancy detection in the time domain, the MSO might have evolved in response to other morphological adaptations that occurred within Mammalia (see The Origins of Spatial Hearing). Increased body (and head) size resulted in a larger interaural distance and a larger larynx, and made it possible to communicate over larger distances (which are best bridged by low-frequency signals). These constraints in turn exerted a selective pressure which favored adaptations that allowed for processing of ITDs (Grothe, 2000 Schnupp and Carr, 2009), as more informative and reliable cues with which to localize relevant sounds or communication calls (since ILDs are negligible at low frequencies). Coincidentally, the “subtraction” mechanism embodied in the LSO, which had developed for ILD detection, is already equipped (pre-adapted) for ITD detection. As has been demonstrated by studies in both cats and chinchillas (Figure 4 Finlayson and Caspary, 1991 Joris and Yin, 1995 Tollin and Yin, 2002, see also Park et al., 1996), response rates of low-frequency LSO neurons are strongly modulated by microsecond changes in ITD. These data therefore clearly establish that the temporal fidelity of the glycinergic MNTB input is sufficient to generate ITD sensitivity in LSO neurons tuned to low frequencies by modulating the excitatory inputs excitatory post-synaptic potentials (EPSPs) in response to fast transients. Hence, the MSO circuit which, in mammals specialized for hearing low-frequency sounds, is dedicated to ITD processing only, can be conceptually regarded as a refined LSO circuit (Figure 5). Interestingly, mammals with good low-frequency hearing typically possess both a large low-frequency limb of the LSO and a well-developed MSO (Grothe, 2000 Grothe et al., 2010). Potentially their combined output is beneficial to the reliable encoding of sound-source positions, because the spatial tuning functions in the two nuclei are mirror images of each other: a purely suppressive coincidence mechanism (i.e., spiking occurs unless binaural coincidence exists) in the LSO is converted into an essentially excitatory coincidence mechanism for the MSO (spiking occurs only if binaural coincidence exists). This conversion is achieved by the addition of two more inputs onto MSO neurons. First, a second excitatory input from the contralateral side is required to allow for binaural excitatory coincidence detection. Second there is also an additional inhibitory ipsilateral input via the LNTB (Figures 5 and 6). Thus, synaptic inhibition represents an essential feature of the MSO circuit. Anatomical and physiological studies have demonstrated that MSO neurons receive relatively few, but unusually strong, glycinergic inputs (Clark, 1969 Grothe and Sanes, 1993, 1994 Kapfer et al., 2002 Werthat et al., 2008 Couchman et al., 2012) that are well balanced in quantity and quantal size with the excitatory MSO inputs (Couchman et al., 2010). Consequently, the MSO must integrate excitatory and inhibitory inputs from both sides, and is not a simple excitatory coincidence detection circuit. The evolutionary pressure that favored such an arrangement is unclear, but it is reasonable to speculate that the system requires a delicate balance of excitation and inhibition in order to accomplish precise temporal integration (see below). Functionally speaking, the two inhibitory inputs may have important implications for the specific ITD tuning of MSO neurons, a topic that is still being debated today. Initially, research focused on the contralateral source of inhibition via the MNTB, as it had been much more extensively characterized (see above). We suggested earlier that the basic role of phase-locked inhibition might actually be the fine-tuning of best delays (ITD of maximal spiking response) in MSO neurons by modulating the time window for binaural excitatory inputs (Figure 6 Brand et al., 2002 Pecka et al., 2008). Specifically, it was suggested that contralateral inhibitory post-synaptic potentials (IPSPs) might arrive at the MSO cell soma slightly in advance of the contralateral EPSPs (Figure 5). This would result in a delay of the net excitatory potential, and thus explain the clustering of contralateral best delays in MSO neurons, which has been observed experimentally and across species (McAlpine et al., 2001 Hancock and Delgutte, 2004 Pecka et al., 2008). This scenario might seem to impose significant temporal demands on the MNTB input, but – as described earlier – it is well established that the same MNTB input suppresses the onset of LSO responses, i.e., that contralateral inhibition arrives simultaneously with the ipsilateral excitation. Thus, it seems plausible that contralateral inhibition should actually be slightly faster than contralateral excitation, and both older and recent work with acute brain slice preparations has confirmed that IPSPs can precede EPSPs at MSO cell somata after contralateral AVCN stimulation (Grothe and Sanes, 1994 Roberts et al., 2013). However, the influence of contralateral inhibition alone is insufficient to explain the extent of modulation suggested by in vivo pharmacological experiments (Zhou et al., 2005 Jercog et al., 2010 Roberts et al., 2013 van der Heijden et al., 2013). To clarify this issue, we recently investigated the ability of the ipsilateral source of inhibition to modulate coincidence detection in the MSO, and found that it had a marked capacity to modulate the timing of binaural coincidence (Figure 6 Myoga et al., 2014). Although more research is required to thoroughly understand the ipsilateral source of inhibition (Leibold, 2010), it is becoming increasingly clear that having two sources of inhibition (instead of just the contralateral source) provides for greater flexibility in modulating the circuit (Figure 6). Thus, while inhibition in the MSO circuit remains a topic of debate, it is reasonable to assume that it serves a central function in the circuit: compared to the ITD-sensitive archetype (i.e., the LSO), an additional (ipsilateral) inhibitory input has evolved in the MSO circuit.

FIGURE 5. The MSO coincidence mechanism is derived from the LSO coincidence mechanism. The schematic depicts temporal relationships of EPSPs and IPSPs, (red and blue traces, respectively) during ipsi-favoring (1, gray), slightly contra-favoring (2, magenta) and strongly contra-favoring (3, green) input combinations. The left-hand and middle column illustrates processing of these synaptic inputs in the LSO for ILDs and ITDs respectively, and ITD processing in the MSO is shown in the right-hand panel. Note that the MSO integrates EPSPs and IPSPs from both the ipsi- and contralateral side, because of the additional excitatory (contralateral) and inhibitory (ipsilateral) inputs compared to the LSO. The panel in the lower row explains how conditions 1𠄳 affect spatial tuning functions in the respective nuclei.

FIGURE 6. Binaural excitation and inhibition of the MSO circuit allows fine-tuning of the coincidence mechanism. (A) MSO neurons receive binaural excitatory inputs from SBCs in the AVCN of either side and binaural inhibitory inputs from LNTB and MNTB, which are innervated by GBCs of the ipsilateral and contralateral AVCN, respectively. (B) ITD tuning function of a gerbil MSO neuron (CF = 683Hz). Note that the peak of the function (�st ITD”) is positioned at a contralateral leading ITD outside of the range of physiological ITDs (gray area), while the slope spans the entire range of physiological ITDs. (C) Upper panel: blocking inhibition in MSO cells in vivo shifts the best ITD toward 0 ITD. Thus, inhibitory inputs tune the ITD of coincidence in MSO cells. Taken from Pecka et al. (2008). Lower panel: combination of ipsi- and contralateral inhibitory inputs (right-sided box) allow for both larger shifts of the best ITD (color-coded) than contralateral inhibition alone (left-sided box). Modified from Myoga et al. (2014).

Dedicated inhibitory pathways also exist within the NL-circuit in chicks and owls that seems to serve multiple functions related to ITD processing (Burger et al., 2011). Neurons of the superior olivary nucleus (SON) provide GABAergic inputs to the NL and form a gain control circuit by reducing the amplitude of excitatory inputs and shortening their duration, thereby ensuring consistent ITD sensitivity across intensity levels (Pe༚ et al., 1996 Dasika et al., 2005 Nishino et al., 2008). SON-mediated inhibition also improves phase-locking precision of both the excitatory inputs and NL responses (Nishino et al., 2008 Burger et al., 2011). Importantly, the inhibition from SON onto NL neurons is not timed (it is decoupled from the phase-locked excitation Yang et al., 1999), and it actually has a depolarizing effect on the NL cells (due to a high intracellular Cl - concentration), which in turn activates low-threshold potassium-channels that lead to shunting of the cell (Hyson et al., 1995 Yang et al., 1999 Burger et al., 2005a). Interestingly, phase-locked GABAergic inhibition that is conveyed by a feed-forward circuit outside the SON has been found to act on NL neurons tuned to very low frequencies to cooperatively enhance ITD tuning together with tonic inhibition (Yamada et al., 2013). It follows that, analogs to the mammalian system, ITD processing at low frequencies requires the (co)-action of timed inhibition. Hence, both in the mammalian and avian ITD system, inhibition serves a prominent function toward refining the ITD sensitivity of the detector neurons. However, the respective neurotransmitters and their associated mode of action and functional time scales are different.

Shared components in ILD and ITD circuits lead to shared coding principles

So far, we have discussed the similar roles of MSO and LSO as binaural discrepancy detectors that share many of their circuit components and design principles. Consequently, similarities are also found in the ways in which particular ITDs and ILDs are reflected in the spiking responses of the respective neurons. Both MSO and LSO neurons exhibit broad, hemispheric tuning to sound-source location, i.e., response rates change monotonically over a large range of azimuthal space (Grothe et al., 2010). Importantly, spatial tuning in both nuclei appears to be more or less stereotypical, with the majority of neurons having their highest spatial sensitivity (the slope of their tuning functions, which conveys most information about changes in location) at frontal positions (Figures 4 and 6 Tollin, 2003 Harper and McAlpine, 2004). For ILDs, this stereotypical arrangement becomes most apparent when (virtual) free-field stimulation is used, suggesting a crucial role for spectral composition of the stimuli in azimuthal sound localization at higher frequencies (Tollin and Yin, 2002). Furthermore, the peak positions of ITD tuning functions have been found to depend on stimulation frequency in many species, irrespective of the head sizes of the species studied (Middlebrooks et al., 1994 McAlpine et al., 2001 Hancock and Delgutte, 2004 Pecka et al., 2008 Werner-Reiss and Groh, 2008). These data have multiple crucial implications: first, that hearing range and the presence of a well-developed MSO, and not body or head size (i.e., physiological ITD range), determines whether a particular species exploits ITDs for sound localization. Since the MSO circuitry is similar in all mammals with low-frequency hearing (Grothe, 2000), neuronal microsecond ITD sensitivity (not spatial acuity in degree, which is a function of interaural size) is also similar across species (Phillips et al., 2012). Second, the frequency-dependence of ITD tuning refutes the notion of a distributed labeled-line representation of azimuthal space (i.e., in which the activity of individual neurons represents the reception of a signal from a fixed direction in space), and have led to numerous speculations on the nature of the underlying coding strategy. The broad tuning functions stimulated the idea of hemispheric, oppositely coding channels on each side of the brain that might be compared upstream of the MSO and LSO (McAlpine et al., 2001 Stecker and Middlebrooks, 2003 Hancock and Delgutte, 2004 Harper and McAlpine, 2004 Figure 7). Note that the MSO output – but not the LSO output – to the midbrain crosses the midline, which unifies the hemispheric polarity of the two within each midbrain side (Figure 7). While the particular nature of this code is currently under debate (Day and Delgutte, 2013 Goodman et al., 2013), one compelling concept relies on the idea that similar activity levels in each channel represent sound-source position at the midline, such that a relative increase in activity in one of the two brain hemispheres would indicate a proportionally contralateral location with respect to the more active brain hemisphere (Figure 7). Psychophysical and functional imaging studies corroborate this scenario of hemispheric coding also in humans (Thompson et al., 2006 von Kriegstein et al., 2008 Magezi and Krumbholz, 2010 Salminen et al., 2010). In particular, using elegant adaptation paradigms, Phillips and Hall (2005), Vigneault-MacLean et al. (2007) have confirmed the presence of a population code that underlies sound localization in humans and also showed that prior stimulation influences subsequent spatial perception. These data pointed the way to more recent discoveries pertaining to how spatial tuning functions can be strongly modulated according to their recent acoustic context. Physiologically, such activity-dependent effects have been demonstrated in the cortex and midbrain (Dahmen et al., 2010 Lee and Middlebrooks, 2011), and even in the MSO and LSO (Magnusson et al., 2008 Park et al., 2008 Stange et al., 2013), suggesting that the primary role of MSO and LSO might not be the encoding of absolute sound-source positions in space (in contrast to the avian system, which employs a labeled line code with a consequently sparse output corresponding to any one position in space), but rather of their relative locations compared to other sound-sources. Similar adaptive coding concepts are well-known in other sensory modalities and will be considered in the context of sound localization in the following section.

FIGURE 7. Both the ILD and ITD code is based on hemispheric tuning functions. The azimuthal tuning function of both LSO and MSO span a wide range of azimuthal space. (A) LSO neurons respond best to ipsilateral sound-source positions (compare Figure 4B). This ipsi-preference is flipped to a contra-preference upstream of the LSO because of the contralateral projections of LSO neurons to the midbrain. (B) MSO neurons respond best to contralateral sound-source positions. This contra-preference is maintained upstream of the LSO because of the ipsilateral projections of MSO neurons to the midbrain.


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MODULATING LEARNING AND MEMORY

The interest in the augmentation of cognitive functions reaches far back into the history of modern humanity. The use of memory techniques, for instance in order to improve rhetorical skills, was already promoted by Marcus Tullius Cicero (� Oratore”, Book II, 55 bc ). One of these methods, the 𠇌icero Memory Method” (Method of loci), a simple memory enhancement method that uses visualization to structure information, is still in use today. The pursuit of cognitive augmentation has since led researchers to take advantage of technical developments in order to achieve a better outcome. In the past decade, scientists have therefore started investigating the impact of various NBS techniques on memory functions.

Learning is a prerequisite for the formation of memory traces and is thought to be dependent on synaptic plasticity mediated by LTP and LTD, which also represent key mechanisms in the effects of NBS on brain functions. This has not only rendered NBS valuable for the investigation of neuroplastic processes associated with learning and memory but also promotes it as a valuable tool to enhance memory functions.

Although TMS is used mostly for diagnostic purposes and the investigation of brain structures contributing to specific functions, tDCS is more often applied to enhance brain functions.

Healthy subjects

W orking memory

In the past decade, researchers have begun examining the effects of WM training on neural correlates and concomitant performance (Jaeggi et al., 2008). These studies have shown that not only can WM capacity be increased via constructive training but also that said training increases the density of cortical D1 dopamine receptors in prefrontal regions (McNab et al., 2009). The neurobiological substrate of WM is an ongoing topic of research however, prefrontal regions are believed to be critically involved. Consistent with such notions, studies exploring the potential for NBS to enhance WM have focused on the prefrontal cortex, generally the DLPFC, and the majority have used verbal WM tasks. In most studies subjects were asked to practice STM or WM tasks concurrently to tDCS, and their WM abilities were assessed either during or afterwards.

Compared with sham stimulation, tDCS with the anode over the left DLPFC (and the cathode right supraorbitally) has been repeatedly reported to enhance WM in healthy subjects (Fregni et al., 2005 Ohn et al., 2008 Mulquiney et al., 2011 Teo et al., 2011 Zaehle et al., 2011). Some researchers have suggested that increasing stimulation intensity (Teo et al., 2011) or duration (Ohn et al., 2008) might lead to more robust effects. Only one study has reported no memory improvement following tDCS with the anode over the left DLPFC (Mylius et al., 2012), and one study reported improvement in STM but not in WM (Andrews et al., 2011). The only study applying tDCS with the anode over the right DLPFC showed no WM effect (Mylius et al., 2012). On the other hand, tDCS with the cathode over the left DLPFC (and the anode right supraorbitally) yielded diverse results in different studies, ranging from memory benefits (Mylius et al., 2012), to no effects (Fregni et al., 2005), and even negative effects (Zaehle et al., 2011). The study by Zaehle et al. (2011) is of particular interest as the authors reported that the negative effects of tDCS with the cathode over the left DLPFC were associated with decreased electroencephalographic power in theta and alpha bands over posterior (parietal) regions. On the other hand, the authors found that improved WM following tDCS with the anode over the left DLPFC was associated with increased power in alpha and theta EEG bands over parietal regions. This study illustrates the potential of studies combining behavioral and neurophysiological outcome measures, and suggests the critical role of corticocortical interactions in memory enhancement. It has been proposed that a more distributed network may subserve WM functions with the posterior parietal cortex (PPC) playing an important role (Mottaghy et al., 2002a Collette et al., 2006). Stimulation might disrupt activity in a given cortical region and thus release activity in a distant connected node, resulting in paradoxical facilitation (Najib and Pascual-Leone, 2011). The specific nature of the stimulation seems important, although, for example, random noise stimulation over the left DLPFC showed no effects (Mulquiney et al., 2011).

In order to explore further the role of parietal structures in WM, Sandrini and colleagues (2012) applied bilateral stimulation over the PPC during a 1-back (STM) or a 2-back (WM) task. They found a double dissociation, with STM being impaired after left-anodal/right-cathodal and WM being impaired after left-cathodal/right-anodal stimulation. They concluded that this dissociation might be due to differential processing strategies in STM and WM. However, the effects might have been mediated by impact on attentional (rather than memory) processes given the fact that only response time, and not accuracy, was affected. Future studies will need to investigate further the contribution of parietal areas and their interaction with prefrontal areas to WM enhancement.

Further studies could examine the duration of effects, the likely synergistic effect of cognitive training with tDCS, or the applicability of tDCS or other NBS methods to enhance WM across the age span, from children to elderly. However, all such studies need carefully to weigh risk�nefit considerations, and should be informed by a thoughtful discussion of the ethical connotations of such enhancement approaches (Rossi et al., 2009 Hamilton et al, 2011 Horvath et al., 2011).

S hort-term memory

Whether NBS can enhance STM in normal subjects is less clear. Studies show less consistent results. This could in part be due to the fact that basic STM tasks are easy for healthy subjects, which leads to ceiling effects. More recent studies have applied adapted tasks, which, however, makes it difficult to compare across studies. Most studies, similar to the literature on WM, have targeted the DLPFC. Two recent studies reported beneficial effects of tDCS with the anode over the DLPFC for an STM task with additional distractors (Gladwin et al., 2012 Meiron and Lavidor, 2013). One study found a gender-dependent improvement in accuracy, with male subjects profiting more from left DLPFC stimulation and female subjects profiting more from right DLPFC stimulation, but only if distractor loads were high (Meiron and Lavidor, 2013). The other study used a modified Sternberg task, which introduced additional distractor stimuli during the delay period (Gladwin et al., 2012). These workers found significant reaction time improvements after stimulation of the left DLPFC. Compared with these studies, Marshall et al. (2005) applied tDCS with either two anodes or two cathodes over DLPFC, with the reference electrodes positioned over the mastoids, and found deleterious effects of STM. This may indicate that the introduction of distractors to an STM task changes underlying neurobiological processes and enables enhancement effects. Improvements after tDCS may be due to either improved selective attention or more successful inhibition of distracting information. Indeed, a recent TMS study has shown that the role of the DLPFC in STM tasks seems to be dependent on the presence of distractors. The stronger the distraction, the more prominent the frontoparietal interactions become, in order to protect relevant memory representations (Feredoes et al., 2011).

Studies in which investigators stimulated parietal areas have yielded partly opposing results. This is true of studies using tDCS and those employing TMS. Regarding TMS experiments, some show worsened STM (Koch et al., 2005 Postle et al, 2006), while the other report improved STM (Hamidi et al., 2008 Yamanaka et al., 2010) after high-frequency parietal stimulation during the delay period. As for tDCS experiments, Berryhill et al. (2010) found impairment in recognition, but not free recall, after tDCS with the cathode over the right parietal cortex (and the anode over the left cheek), whereas Heimrath and coworkers (2012), positioning the cathode over the right parietal cortex (and the anode over the contralateral homologous area), found an improved capacity in a delayed match-to-sample task after tDCS when stimuli were presented in the left visual hemifield (STM for stimuli presented in the left hemifield decreased). Interestingly, Heimrath et al. used concurrent tDCS and EEG, and found a decrease in oscillatory power in the alpha band after cathodal stimulation. As alpha activity is assumed to reflect inhibition of distractors (Klimesch, 1999), the authors suggested that this measure might indicate memory performance. This study again illustrates the potential of experiments combining behavioral and neurophysiological outcome measures with NBS.

Finally, one study probed the cerebellum and found an abolishment of practice-dependent improvements in response time in a Sternberg task, regardless of whether the anode or the cathode was placed over the cerebellum (and the other electrode over the vertex) (Ferrucci et al., 2008). The contribution of the cerebellum to STM was also probed with single-pulse TMS by Desmond and colleagues (2005), who also found a negative effect on response time in the Sternberg task. Whether other cerebellar stimulation paradigms can induce an enhancement of STM remains unexplored.

G eneral memory and learning

Researchers attempting to enhance learning processes have targeted various neural regions. Such diverse approaches again render it difficult to single out a pattern regarding stimulatory condition, mechanisms, and outcome. Most studies have applied tDCS during the learning phase, and most have targeted the left DLPFC or other left prefrontal areas. Generally, studies report memory improvement following tDCS with the anode over DLPFC (Kincses et al., 2004 Javadi and Walsh, 2012 Javadi et al., 2012) or other prefrontal areas (De Vries et al., 2010), and worsening memory after tDCS with the cathode over DLPFC (Elmer et al., 2009 Hammer et al., 2011 Javadi and Walsh, 2012 Javadi et al., 2012) or other prefrontal areas (Vines et al., 2006). However, in interpreting their results, investigators have often made the overly simplistic assumption that the effects of tDCS can be accounted for by the neurobiological effect of one of the electrodes, the anode enhancing and the cathode suppressing activity in the brain area under them. Yet, it is important to remember that tDCS is not monopolar and that all electrodes are active. Thus the brain is exposed to a flow of current with opposite faradizing effects of the anode and the cathode. Therefore, to speak of anodal tDCS or cathodal tDCS is inaccurate.

Few studies have targeted right prefrontal areas. One study reported no effects in an episodic verbal memory task after tDCS with either anode or cathode over the right prefrontal region (Elmer et al., 2009). Two studies showed that the learning process of threat detection in a virtual reality environment and the time required to learn this skill can be improved following tDCS with the anode over the right prefrontal (Bullard et al., 2011 Clark et al., 2012) or right parietal region (Clark et al., 2012). Furthermore, Bullard and colleagues (2011) found that applying tDCS at the beginning of the learning phase significantly enhanced learning in comparison with findings in experienced learners (after 1 hour of training).

Bilateral stimulation (anode and cathode over homologous areas of either hemisphere) has been applied in a few studies (Marshall et al., 2004, 2011 Boggio et al., 2009 Chi et al., 2010 Cohen Kadosh et al., 2010 Penolazzi et al., 2010 Jacobson et al., 2012). Jacobson and coworkers (2012) applied bilateral tDCS (anodal left, cathodal right, or vice versa) over the parietal lobe during encoding. They found improved verbal memory only when the anode was placed over the left hemisphere and the cathode over the right hemisphere. Another study investigating the contribution of the parietal cortex to numerical learning applied bilateral tDCS during a training phase of 6 days (Cohen Kadosh et al., 2010). While right-anodal/left-cathodal stimulation improved learning significantly, right-cathodal/left-anodal stimulation decreased learning compared with sham tDCS.

Penolazzi and colleagues (2010) applied bilateral tDCS (anode left and cathode right, or vice versa) over the frontotemporal cortex during encoding and found facilitated recall of pleasant images after right-anodal/left-cathodal tDCS, whereas left-anodal/right-cathodal tDCS facilitated recall of unpleasant images. These results support a theoretical model (specific valence hypothesis) according to which the right and left hemispheres are specialized in the processing of unpleasant and pleasant stimuli respectively. Another group applying bilateral stimulation (anodal left, cathodal right, or vice versa) over the anterior temporal lobe assessed visual memory (Chi et al., 2010) and also reported an improvement in memorizing different types of shape after right-anodal/left-cathodal stimulation, but no effects when applying an inverse stimulation pattern.

One set of studies has investigated effects of bilateral anodal stimulation over DLPFC during sleep and wakefulness. In their first study, Marshall and colleagues (2004) reported an improvement of memory consolidation when applying intermittent (on/off 15 seconds) anodal tDCS simultaneously over both DLPFCs during slow-wave (nonrapid eye movement, non-REM) sleep but not during wakefulness. In a second study they investigated state-dependent effects, and found enhanced theta activity when transcranial slow oscillation stimulation (tSOS) was applied during wakefulness (Kirov et al., 2009). Memory enhancement occurred only when tSOS was applied during learning, but not after learning. In their third study, Marshall and colleagues (2011) applied anodal theta-tDCS (tDCS oscillating at 5 Hz) during REM sleep and non-REM sleep, which led to increased gamma-band activity and decreased memory consolidation respectively. The data from these studies illustrate the potential of transcranial current stimulation at specific stimulation frequencies selectively to modulate specific brain oscillations. This NBS method provides an interesting approach for investigating the relation between cortical brain rhythms, sleep-related processes, and memory functions.

Some studies have reported apparently contradictory results, highlighting the need for further investigation of the mechanisms of action underlying tDCS and TMS. Boggio et al. (2009) found decreased �lse memories” utilizing anodal tDCS over the left anterior temporal lobe, or bilateral (left-anodal/right-cathodal) tDCS. However, the same researchers reported a nearly identical effect after applying 1-Hz rTMS over the same region, a protocol that is believed to suppress activity of the targeted brain area (Gallate et al., 2009). Of course, it is possible that the behavioral effect might be related to trans-synaptic network effects, rather than being mediated by the targeted brain region. Indeed, a study using single-pulse TMS reported a facilitatory effect on verbal memory after stimulating the right inferior PFC (Kahn et al., 2005), presumably due to interhemispheric paradoxical facilitation effects. This would be consistent with another study that found an improvement in verbal memory after stimulating the left inferior PFC with 7-Hz rTMS bursts (Köhler et al., 2004). Furthermore, a paired-pulse protocol known to induce facilitatory effects led to memory improvements after stimulation of the left and right DLPFC in verbal as well as nonverbal episodic memory. The combination of stimulation techniques and other methods, such as EEG and fMRI, allows their inherent advantages to be combined to help answer these open questions.

Elderly healthy subjects

Basic memory research includes mostly young and healthy subjects. However, one of the key topics in the domain of NBS research concerns the changes of interhemispheric balance and the increased compensatory recruitment of brain areas with aging. As memory represents an overarching topic for the elderly, it is crucial to promote research that investigates these changes and provides information as to how to enhance memory functions. Furthermore, research with healthy elderly subjects is vital if we want to translate it into the clinical setting, as patients with memory deficits are mostly older. A newly emerging field has started to investigate memory enhancement in elderly subjects and underlying models (Rossi et al., 2004 Solé-Padullés et al., 2006 Manenti et al., 2011 Fl཮l et al., 2012).

The “Hemispheric Asymmetry Reduction in Older Adults” (HAROLD) model states that prefrontal activity during cognitive performance becomes less lateralized with advancing age (Cabeza, 2002). Manenti and colleagues investigated the differential assumptions of the HERA model (young subjects) and the HAROLD model (elderly subjects), suggesting that hemispheric asymmetry is reduced with age. Interestingly, they could show that low-performing elderly subjects continue showing prefrontal asymmetry, whereas high-performing elderly individuals show reduced asymmetry indicative of compensatory mechanisms (Manenti et al., 2011).

Although lateralized activations within the PFC can be observed in younger subjects during episodic memory tasks (Rossi et al., 2001), this asymmetry vanishes progressively with advancing age, as indicated by bilateral interference effects (Rossi et al., 2004).

Conversely, the predominance of left DLPFC effect during encoding was not abolished in older subjects, indicating its causal role for encoding along the lifespan. However, this study did not differentiate between high- and low-performing subjects. Another study supported the assumption that higher performance is associated with more bilateral recruitment of brain areas and that stimulation may be able to promote the recruitment of additional brain areas to compensate for age-related decline. Solé-Padullés and colleagues (2006) found improved performance in associative learning after 5-Hz offline rTMS, which was accompanied by additional recruitment of right prefrontal and bilateral posterior brain regions.

A tDCS study showed improvements in spatial learning and memory in elderly subjects (mean 62 years) when stimulating during encoding (Fl཮l et al., 2012). Anodal stimulation over the right temporoparietal cortex improved free recall 1 week later compared with sham stimulation. No immediate learning differences were observed, which indicates that retention (less decay) rather than encoding was affected by the stimulation.

To summarize, several studies have found different results following the stimulation of the DLPFC in young and elderly healthy subjects in accordance with the HAROLD model (Cabeza, 2002). These differences could be due to changes in interhemispheric balance and recruitment of different brain areas for the same tasks, which could arise due to compensatory mechanisms. It remains to be further elucidated whether these changes reflect local or distributed mechanisms, whether compensatory recruitment of additional brain areas is associated with higher performance levels and could be enhanced by NBS.

Patients

Compared with the wealth of studies that have been done with healthy and mostly young subjects, studies on patients are rather sparse (see Table 55.1 ). The evidence is encouraging and calls for further investigation of the combined application of NBS and neuropsychological therapy. Besides behavioral measures, these studies should ideally include other measurements, such as assessment of brain plasticity or memory-specific neurophysiological outcomes. The work on patients with stroke is very preliminary, and more studies with larger patient numbers and better control of lesion location are needed. In one crossover, sham-controlled study, Jo et al. (2009) applied tDCS with the anode over the left DLPFC (and the cathode over the contralateral supraorbital area) in a 2-back task to 10 patients with unilateral, right-hemispheric, ischemic, or hemorrhagic strokes (1𠄴 months poststroke). After a single stimulation session, performance accuracy but not reaction time improved significantly. Enhancement of memory functions has been more extensively investigated in patients with AD and Parkinson’s disease (PD). These findings provide evidence that NBS could be a safe and useful tool in restoring/compensating brain functions through activation of primary and compensatory networks that underlie memory functions.

A lzheimer’s disease

A few studies have demonstrated effects of NBS on cognitive functions in AD (6 TMS, 3 tDCS). The first studies that used NBS in AD looked primarily at language and not memory functions. Cotelli and colleagues used rTMS (20 Hz) over the left and right DLPFC and reported positive effects for both hemispheres. They applied a single online session of rTMS in two crossover, sham-controlled studies (Cotelli et al., 2006, 2008). In the first study they reported improved accuracy in action naming, but not object naming, for all patients (Cotelli et al., 2006). In the second study they could replicate the positive results for action naming however, object naming also improved significantly, although only in moderately to severely impaired patients (Cotelli et al., 2008). The authors hypothesized that the lack of improvement in object naming may be due to a ceiling effect. Furthermore, the bilateral effect could have been due to compensatory activation of right hemispheric resources.

In a third placebo-controlled study the same authors tested various functions, including memory, executive functions, and language in patients with moderate AD (Cotelli et al., 2011). This study entailed 4 weeks of daily sessions of 20-Hz rTMS to the left DLPFC. Although they found significant improvements in sentence comprehension after 10 sessions (with no further improvement after 20 sessions), they did not find any improvements in memory and executive functions (Cotelli et al., 2011). This lack of improvement could be due to the fact that the patients were not doing any specific concomitant cognitive training. Alternatively, the lack of memory effects could be related to the targeted brain region.

Bentwich and colleagues (2011) interleaved cognitive training and rTMS (10 Hz) during 30 sessions while stimulating six different brain regions (Broca, Wernicke, right and left DLPFC and parietal cortices). During each session three of these regions were stimulated while patients did cognitive tasks that were developed to fit each of these regions. Improvements in cognitive functions were significant, as measured using the cognitive subscale of the Alzheimer’s Disease Assessment Scale (ADAS-Cog), and were maintained for 4.5 months after the training. A case report (Haffen et al., 2012) showed an improvement in episodic memory (free recall) and processing speed following 10 sessions of rTMS (10 Hz) over the left DLPFC. These are open trials and, obviously, sham-controlled interventions are needed. However, the results are promising and warrant follow-up. In a sham-controlled trial, Ahmed and colleagues (2012) assigned 45 patients with AD to three different treatment groups to study the effects of high- or low-frequency rTMS (20 Hz, 1 Hz), or sham stimulation. Patients received treatment on 5 consecutive days without combined cognitive training. Mildly to moderately impaired patients receiving high-frequency rTMS improved significantly on all scales (Mini Mental State Examination (MMSE), Instrumental Daily Living Activity Scale, Geriatric Depression Scale), and maintained these improvements for 3 months. However, severely impaired patients did not respond to the treatment.

Two crossover studies applied tDCS for one session and reported improvements in visual recognition memory following stimulation of the left DLPFC and temporoparietal cortex (TPC) (Boggio et al., 2009), and in word recognition following stimulation of the bilateral TPC (Ferrucci et al., 2008). In the first study, the authors applied 15 minutes of anodal, cathodal, and sham stimulation over bilateral TPC on three different sessions in patients with mild AD. While anodal tDCS led to an improvement, cathodal stimulation led to impairments in word recognition. No effects were observed in a visual attention task (Ferrucci et al., 2008). In the second study, mildly to moderately impaired AD patients received anodal tDCS over the left DLPFC, the left TPC, or sham stimulation. Stimulation over both DLFPC and TPC resulted in a significant improvement in visual recognition. No effects were observed on selective attention or a visual delayed match-to-sample task.

Possibly, tDCS-induced changes in cholinergic activity contributed to these improvements. A recent study reported a significant change of SAI (ISI 2 ms) in the motor cortex of healthy subjects after anodal stimulation, while the resting motor threshold and amplitudes of motor evoked potentials did not change (Scelzo et al., 2011). This could explain the positive impact of tDCS on memory functions in the above-mentioned studies. Future studies measuring behavioral along with neurophysiological effects and exploring correlations between them would be desirable.

P arkinson’s disease

Two studies have applied TMS or tDCS with the aim of improving cognitive functioning in PD. The first study compared the effects of active or sham rTMS and fluoxetine or placebo in patients with PD with concurrent depression (Boggio et al., 2005). The authors applied 15-Hz rTMS over the left DLPFC for 10 daily sessions, and assessed cognitive functions at baseline, and 2 and 8 weeks after the treatment. Treatments were not combined with cognitive training or psychotherapy. After 2 weeks both interventions led to similar improvements in the Stroop Test and the Wisconsin Card Sorting Test (executive functions), and the Hooper (visuospatial functions). Furthermore, depression rates improved significantly in both groups. However, no improvements were reported in STM or WM (digits forward and backward). Eight weeks after treatment, these improvements declined slightly but remained significant.

The second study found improved accuracy in a 3-back task during a single session of anodal tDCS over the left DLPFC. Improvement was significant at a stimulation intensity of 2 mA but not at 1 mA (Boggio et al., 2006).

Cognitive impairments in PD are often associated with depression symptoms, which occur in about 35% of patients. Furthermore, dementia is common in these patients with a point prevalence of 30% (Aarsland and Kurz, 2010). Further studies are needed to investigate underlying processes leading to cognitive impairments. Moreover, studies should evaluate the efficacy of repetitive NBS in combination with cognitive training for this patient population.


Eat [ edit ] [ add listing ]

This guide uses the following price ranges for a typical meal for one, including soft drink:
Budget Under R60
Mid-range R60 to R120
Splurge Over R120

Food in Cape Town is generally of high quality. However, do not buy fresh fruit from street vendors, as it commonly makes travelers sick. The wines are much celebrated, but the surrounding region is also a major fruit producer, and the Karoo lamb is widely regarded. Seafood caught locally is superlative, but ironically much of it goes internationally (e.g., tuna for sushi) because of the prices that can be achieved. Ask about the local linefish -- yellowtail, cape salmon, kingklip, kabeljou and others are great eating. Oysters in season are also exceptional, farmed and wild from Knysna or wild flown in from Namibia.

As one of the main tourist spots is the V&A waterfront, you will find a broad range of restaurants, but they are often crowded and expensive. Another highlight is the area around Long Street with its many cafés and restaurants (frequented by a multi-ethnic clientèle), while the trendy area of De Waterkant between Bo Kaap and Green Point above Somerset Road also boasts good food and a great vibe. Dine with supermodels and other beautiful people in Camps Bay, which has many hip eateries and nightspots overlooking the beach along Victoria Road. The Old Biscuit Mill, in the center of Woodstock, is a lovely Saturday market teeming with quality drinks and foods for a friendly price.

Bree street is the new trendy street in the city and is slowly becoming the new Long street. With a wide choice of restaurants, bars, specialist food outlets this is where both locals and tourists hang out. Anything from budget meals to international cuisine - popular for lunch and dinners.

Kloof Street & Park Road in Gardens area is the latest hip urban cool area and is an excellent eating place away from the tourist throngs with a variety of bistro / sushi / hipster type places serving the young professional and bohemian crowd.

Farther afield, Hout Bay on the west side of the Cape Peninsula is very good for fresh crayfish (lobsters - they have become quite expensive, around R300, though). Kalk Bay on the east side of the peninsula offers a big variety of fresh fish, do check out The Brass Bell. The restaurants in nearby Simon's Town are also good.

Do not neglect the Cape Winelands for food if you have a car. In Stellenbosch, Spier has several restaurants, including the fun, afro-chic Moyo, and many wine estates offer food of different types and quality. The village of Franschhoek is the culinary navel of the wine region, with Le Quartier Francais a perennial five-star winner, but only one of many excellent restaurants. In the Constantia Valley there are number of great restaurants including Pastis Brasserie, Wasabi, The River Cafe, La Colombe and the Constantia Uitsig Restaurant.

NB: Make sure you know what the price is before you order rare delicacies in restaurants as there have been a few rare but high-profile cases of heinous overcharging where the price is not on the menu, particularly for perlemoen (abalone) and crayfish (similar to lobster).

Budget [ edit ]

  • Bakoven , Southern Life Building, 10 Riebeeck Street , ☎ +27 21 419 1937 . Coffee shop and light meals.  edit
  • Cafe Eco , 90 Long Street , ☎ +27 21 422 2299 , [97]. Cheap, relaxed, environmentally-friendly coffee shop. A favourite with backpackers.  edit
  • Table Mountain Restaurant , On top of Table Mountain, close to the Upper Cable Station . Open 08:30 to 18:30, with extended hours during December and January . A 120 seat, self service restaurant. No booking required.The restaruant is closed when the Table Mountain Cable Car is not operating. From R20 for a simple breakfast .  edit

Midrange [ edit ]

  • A Tavola , Wilderness Road, Claremont ( Across the road from the Kingsbury Hospital, just off Main Road. ), ☎ +27 (0)21 671-1763 , [98]. 12:00 pm – 3:00 pm 6:00 pm – 10:00 pm . A casual, glass-fronted Italian restaurant popular with locals. Daily specials book reservations online or phone. ( 18.467867 , 33.985529 )  edit
  • Africa Café , 108 Shortmarket Street , ☎ +27 (0)21 422-0221 ( [email protected] ), [99]. Affordable and very good. Maybe the best restaurant in Cape Town for African cuisine. Lower to medium price range. Serves fixed menu, all you can eat of 12 - 15 different dishes.  edit
  • Bayfront Blu , Two Oceans Aquarium , ☎ +27 (0)21 419-9086 . Offers breakfast and coffee all day and also serves good seafood, like Swahili prawn curry. Tables offer view on water and Table Mountain.  edit
  • Biesmiellah , Corner Upper Wale/Pentz Street , ☎ +27 (0)21 423-0850 . One of the oldest restaurants around, known for its Malay kitchen. No alcoholic drinks are available.  edit
  • Col'Cacchio Pizzeria , 42 Hans Strijdom Avenue Foreshore ( Take N1 on M18, take right into River Rd and left into Hans ), ☎ 0214194848 , [100]. Italian dishes made to order. Midrange .  edit
  • Five Flies , 14-16 Keerom Street , [101]. Enjoy a wonderful, multi-course meal in a stylish restaurant housed in one of Cape Town's oldest still-standing buildings. Favourite of local diplomats. Menu changes regularly book reservations online.  edit
  • Hildebrands , V&A Waterfront . Offering standard Italian fare of pizzas and pastas, but the quality is not up to par.  edit
  • Jewel Tavern , 101 St Georges Mall Street, City Bowl ( At the intersection of Church Street and St Georges Mall Street ), ☎ +27 (0)21 422-4041 . Increasingly popular Chinese restaurant. Preferred destinations for Cape Town's bon viveurs. Guest can watch how their meals are prepared. Note this is a local spot for fisherman/boat workers coming in and spending a few days into the harbour. It is a very authentic spot with no frills. Most of the staff do not speak English, but the food is delicious.  edit
  • 95 Keerom , 95 Keerom Street . A top class Italian restaurant with modern décor and a trendy atmosphere.  edit
  • Lolas , ( Across from Long Street Café ). Vegetarian food with local colour and great karma. Good conversation and even better meals. Mingle with dreadlocks, artsy types and brooding poets.  edit
  • Long Street Café , 259 Long Street . Very popular, European kitchen, which serves up tasty drinks.  edit
  • Mama Africa , 178 Long Street , ☎ +27 (0)21 426-1017 . Open Monday to Saturday. Restaurant is open 7PM till late, the bar is open 4:30PM till late . African style tourist restaurant offering local and African meals, like Bobotie and Potjiekos, but also springbok, kudu and crocodile steak. Good range of wines at affordable prices. Live marimba music some nights.  edit
  • Renaissance Cafe , Mainstream Centre, Main Road, Hout Bay (next door to the Post Office) , ☎ +27 (0)21 790-7202 . Best coffee in Hout Bay, set in a stunning courtyard. Open 8:30AM to 6PM every day. Well worth a visit!  edit
  • Rhodes Memorial Restaurant , Rhodes Memorial , ☎ +27 (0)21 689-9151 ( [email protected] ). Situated in the Table Mountain National Park directly behind the famous Rhodes Memorial. The restaurant has stunning views over the northern and eastern Cape Town suburbs and the Hottentots Holland mountain range. The menu is diverse and caters to all tastes, but its the desserts that really rate a mention, be sure to tuck into some scones!  edit
  • The Ritz Hotel , cnr. Camberwell and Main Roads, Sea Point , ☎ +27 (0)21 439-6010 . Has a revolving restaurant on the top floor of the hotel. Good food, good views, soft background live piano. A bar and smoking room is available one floor below the restaurant. You do not have to be a resident at the hotel to get a booking at the restaurant. NB(The floor has a small non revolving ledge next to the wall. Do not put your valuables on it as your table will be half way around the building before you realize that you have been separated from your belongings.)  edit
  • Sunflower Health Café , 111 Long Street . Vegetarian restaurant, with a limited range of satisfying warm meals.  edit
  • Tasca de Belem , Victoria Wharf, shop 154, Piazza Level, V&A Waterfront , ☎ +27 (0)21 419-3009 . A very good Portuguese restaurant that offers some exquisite meals.  edit
  • Tong Lok , 10 Link Rd Parklands, Parklands Centre , ☎ +27 (0)21 556 8722 . The best Chinese restaurant and take-away that serves anything from vegetables, to seafood, sushi and other Japanese foods.  edit
  • Willoughby's , Victoria Wharf, V&A Waterfront . Has some of the best seafood including excellent sushi at very good prices.  edit

Splurge [ edit ]

  • Bistro , 69 Victoria Road, Camps Bay, Cape Town , ☎ +27 021 430 4444 ( [email protected] , fax : +27 (0) 21 438 4433 ), [102]. Mo-Fr , Sa-Su . Lunches feature sandwiches, salads and pastas showcasing imaginative combinations of only the finest ingredients R90 .  edit
  • Von Kamptz Restaurant , 7 Chilworth Road, Camps Bay, Cape Town , ☎ +27 021 437 8300 ( [email protected] ), [103]. The tender signature Chalmar Beef Fillet is the ever popular dish – either cooked on the grill, or over open fire during the summer months. R250 .  edit
  • Ashton's Restaurant at Greenways , 1 Torquay Avenue Upper Claremont , ☎ 021-761-1792 . Mo-Su 7AM-10PM . World class fine dining restaurant that offers international cuisine with a South African twist.  edit

Desktop browsers

Chrome

  1. In the browser bar, enter:
  2. At the top of the "Clear browsing data" window, click Advanced .
  3. Select the following:
    • Browsing history
    • Download history
    • Cookies and other site data
    • Cached images and files

From the "Time range" drop-down menu, you can choose the period of time for which you want to clear cached information. To clear your entire cache, select All time .

Firefox

If the menu bar is hidden, press Alt to make it visible.

Microsoft Edge

Microsoft Edge Legacy support ended on March 9, 2021. If you still have Edge Legacy, UITS recommends installing the new Chromium-based Microsoft Edge by running Windows Update.

  1. In the top right, click the Hub icon (looks like star with three horizontal lines).
  2. Click the History icon (looks like a clock), and then select Clear all history .
  3. Select Browsing history , then Cookies and saved website data , and then Cached data and files . Click Clear .
  4. After the "All Clear!" message appears, exit/quit all browser windows and re-open the browser.

Opera

  1. From the Opera menu, select Settings , then Privacy & Security , and then Clear browsing data. .
  2. In the dialog box that opens, from the "Obliterate the following items from:" drop-down menu, select The beginning of time .
  3. Select the following:
    • Browsing history
    • Download history
    • Cookies and other site data
    • Cached images and files
  4. Click Clear browsing data .
  5. Exit/quit all browser windows and re-open the browser.

Safari 8 and later

  1. From the Safari menu, select Clear History. or Clear History and Website Data. .
  2. Select the desired time range, and then click Clear History .
  3. Go to Safari > Quit Safari or press Command-Q to exit the browser completely.

This is document ahic in the Knowledge Base.
Last modified on 2021-02-08 11:19:47 .


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