Projections of the medial geniculate nucleus to layer 1 of the auditory cortex in the cat traced with horseradish peroxidase

Niimi, Kahee; Ono, Katsuhiko; Kusunose, Masahiro

doi:10.1016/0304-3940(84)90103-4

Cited by 33 publications

(15 citation statements)

References 6 publications

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“…In their study of A1 in cats, Huang and Winer (2000) noted that some of the thickest TC axons were found after injections of the MGm. Upon reaching L1, these axons (up to 6 μm in diameter) ran horizontally in LIa over long distances and appeared to come from the large magnocellular neurons unique to the MGm (Mitani et al 1987; Niimi et al 1984). These may correspond to the same class of large-diameter axons found in the macaque monkey, which were found to arise from calbindin immunoreactive neurons in the MGm (Hashikawa et al 1995).…”

Section: Discussionmentioning

confidence: 99%

Differential maturation of vesicular glutamate and GABA transporter expression in the mouse auditory forebrain during the first weeks of hearing

et al. 2015

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Vesicular transporter proteins are an essential component of the presynaptic machinery that regulates neurotransmitter storage and release. They also provide a key point of control for homeostatic signaling pathways that maintain balanced excitation and inhibition following changes in activity levels, including the onset of sensory experience. To advance understanding of their roles in the developing auditory forebrain, we tracked the expression of the vesicular transporters of glutamate (VGluT1, VGluT2) and GABA (VGAT) in primary auditory cortex (A1) and medial geniculate body (MGB) of developing mice (P7, P11, P14, P21, adult) before and after ear canal opening (~P11–P13). RNA sequencing, in situ hybridization, and immunohistochemistry were combined to track changes in transporter expression and document regional patterns of transcript and protein localization. Overall, vesicular transporter expression changed the most between P7 and P21. The expression patterns and maturational trajectories of each marker varied by brain region, cortical layer, and MGB subdivision. VGluT1 expression was highest in A1, moderate in MGB, and increased with age in both regions. VGluT2 mRNA levels were low in A1 at all ages, but high in MGB, where adult levels were reached by P14. VGluT2 immunoreactivity was prominent in both regions. VGluT1+ and VGluT2+ transcripts were co-expressed in MGB and A1 somata, but co-localization of immunoreactive puncta was not detected. In A1, VGAT mRNA levels were relatively stable from P7 to adult, while immunoreactivity increased steadily. VGAT+ transcripts were rare in MGB neurons, whereas VGAT immunoreactivity was robust at all ages. Morphological changes in immunoreactive puncta were found in two regions after ear canal opening. In the ventral MGB, a decrease in VGluT2 puncta density was accompanied by an increase in puncta size. In A1, peri-somatic VGAT and VGluT1 terminals became prominent around the neuronal somata. Overall, the observed changes in gene and protein expression, regional architecture, and morphology relate to—and to some extent may enable— the emergence of mature sound-evoked activity patterns. In that regard, the findings of this study expand our understanding of the presynaptic mechanisms that regulate critical period formation associated with experience-dependent refinement of sound processing in auditory forebrain circuits.

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Section: Discussionmentioning

confidence: 99%

Differential maturation of vesicular glutamate and GABA transporter expression in the mouse auditory forebrain during the first weeks of hearing

et al. 2015

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“…This nucleus projects to all auditory cortical fields, both tonotopic and non-tonotopic, as well as some adjacent non-auditory regions of the temporal cortex including agranular insular, ectorhinal, perirhinal and visceral cortices (Linke and Schwegler, 2000). Morover, in contradistinction to the lemniscal MGv, the MGm does not project to layers III and IV but rather to layers I and also VI (Huang and Winer, 2000; Linke and Schwegler, 2000; Niimi and Naito, 1974; Niimi et al, 1984; Ryugo and Killackey, 1974). Remarkably, the layer I projections within auditory cortical fields appear to be via giant axons.…”

Section: Relevant Anatomy and Physiology Of The Medial Geniculate mentioning

confidence: 92%

The medial geniculate, not the amygdala, as the root of auditory fear conditioning

2011

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The neural basis of auditory fear conditioning (AFC) is almost universally believed to be the amygdala, where auditory fear memories are reputedly acquired and stored. This widely-accepted amygdala model holds that that the auditory conditioned stimulus (CS) and the nociceptive unconditioned stimulus (US) first converge in the lateral nucleus of the amygdala (AL), and are projected independently to it from the medial division of the medial geniculate nucleus (MGm) and the adjacent posterior intralaminar nucleus (PIN), which serve merely as sensory relays. However, the four criteria that are used to support the AL model, (a) CS-US convergence, (b) associative plasticity, (c) LTP and (d) lesion-induced learning impairment, are also met by the MGm/PIN. Synaptic and molecular approaches supporting the AL also implicate the MGm/PIN. As both the AL and its preceding MGm/PIN are critically involved, we propose that the latter be considered the "root" of AFC.

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“…In cat AI, thalamocortical axons from the ventral nucleus of the medial geniculate body end in layers IIIb and IV (Sousa-Pinto, 1973), and those from the medial division target layers I and VI (Mitani et al, 1984;Niimi et al, 1984). Layers III and IV receive substantial corticocortical input (Diamond et al, 1968), and commissural axons terminate mainly in layer III and progressively less in layers I, V, and VI (Code and Winer, 1986).…”

Section: Role Of Layer VI Pyramidal Cells In Cortical Processingmentioning

confidence: 99%

Layer VI in cat primary auditory cortex: Golgi study and sublaminar origins of projection neurons

Prieto

Winer

1999

J. Comp. Neurol.

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The organization of layer VI in cat primary auditory cortex (AI) was studied in mature specimens. Golgi‐impregnated neurons were classified on the basis of their dendritic and somatic form. Ipsilateral and contralateral projection neurons and the corticogeniculate cells of origin were labeled with retrograde tracers and their profiles were compared with the results from Golgi studies. Layer VI was divided into a superficial half (layer VIa) with many pyramidal neurons and a deeper part (layer VIb) that is dominated by horizontal cells. Nine types of neuron were identified; four classes had subvarieties. Classical pyramidal cells and star, fusiform, tangential, and inverted pyramidal cells occur. Nonpyramidal neurons were Martinotti, multipolar stellate, bipolar, and horizontal cells. This variety of neurons distinguished layer VI from other AI layers. Pyramidal neuron dendrites contributed to the vertical, modular organization in AI, although their apical processes did not project beyond layer IV. Their axons had vertical, intrinsic processes as well as corticofugal branches. Horizontal cell dendrites extended laterally up to 700 μm and could integrate thalamic input across wide expanses of the tonotopic domain. Connectional experiments confirmed the sublaminar arrangement seen in Nissl material. Commissural cells were concentrated in layer VIa, whereas corticocortical neurons were more numerous in layer VIb. Corticothalamic cells were distributed more equally. The cytological complexity and diverse connections of layer VI may relate to a possible role in cortical development. Layer VI contained most of the neuronal types found in other layers in AI, and these cells form many of the same intrinsic and corticofugal connections that neurons in other layers will assume in adulthood. Layer VI, thus, may play a fundamental ontogenetic role in the construction and early function of the cortex. J. Comp. Neurol. 404:332–358, 1999. © 1999 Wiley‐Liss, Inc.

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Projections of the medial geniculate nucleus to layer 1 of the auditory cortex in the cat traced with horseradish peroxidase

Cited by 33 publications

References 6 publications

Differential maturation of vesicular glutamate and GABA transporter expression in the mouse auditory forebrain during the first weeks of hearing

Differential maturation of vesicular glutamate and GABA transporter expression in the mouse auditory forebrain during the first weeks of hearing

The medial geniculate, not the amygdala, as the root of auditory fear conditioning

Layer VI in cat primary auditory cortex: Golgi study and sublaminar origins of projection neurons

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