The anterior dorsal nucleus is as significant for the dorsal fields of the auditory cortex as the ventral nucleus of the medial geniculate body is for the temporal fields of the auditory cortex. 
The parvalbumin pathway, ascending from the central nucleus of the inferior colliculus, is the more direct and terminates in the ventral nucleus. ventral nucleus neurons are sharply tuned, tonotopically organized and consistent in their responses.
The smaller ventral nucleus (Pv) which stains darkly for the Cat-301 antigen, projects to these same cortical areas, with a retinotopic pattern.
Dominant topographical projections from the ventral nucleus to area EM confirmed physiological reports that it may be considered a primary auditory area (AI).
To investigate subcortical contributions to cortical reorganization, the frequency organization of the ventral nucleus of the medial geniculate body (MGv) in six normal adult cats and in eight cats with restricted unilateral cochlear lesions was investigated using multiunit electrophysiological recording techniques.
Notably, Kv3.1 mRNA was not expressed in neurons of the medial and lateral superior olive and a subpopulation of neurons in the ventral nucleus of the lateral lemniscus.
A histological study with light microscopy revealed degeneration of neurons in the ventral nucleus of the medial geniculate body (MGv) in the decreased group, whereas the neurons in this region were preserved in the non-decreased group.
These include: cochlear nucleus afferents to periolivary (lateral nucleus of the trapezoid body, LNTB) cells that project to the inferior colliculus; cortical afferents to periolivary (ventral nucleus of the trapezoid body, VNTB) cells that project to the cochlear nucleus; and serotoninergic and noradrenergic afferents to periolivary (LNTB and VNTB) cells that project to the cochlear nucleus.
In monkeys, the ventral nucleus of the medial geniculate complex projects in parallel to a core of three primary-like auditory areas, AI, R, and RT, constituting the first stage of cortical processing.
In the diencephalon, labeled cells were present in all the mid-line and intralaminar thalamic nuclei; the lateral posterior, pulvinar and suprageniculate nuclei; the ventral nucleus of the lateral geniculate body and the medial geniculate body.
Single-unit responses were recorded from the ventral nucleus (Vn) and lateral part of the posterior group of thalamic nuclei (Po), tonotopic subdivisions of the MGB.
Auditory information is relayed from the ventral nucleus of the medial geniculate complex to a core of three primary or primary-like areas of auditory cortex that are cochleotopically organized and highly responsive to pure tones.
We present here the terminal morphology of retinal axons in the lateral geniculate body and superior colliculus, verifying earlier studies, and also document novel findings on the configuration of retinal axon endings in the ventral nucleus of the lateral geniculate body, intergeniculate leaflet, suprachiasmatic nucleus, and in the nuclei of the accessory optic tract.
Input projections were observed ipsilaterally from: the medial and lateral superior olivary nuclei; the superior paraolivary nucleus; the dorsolateral and anterolateral periolivary nuclei; the dorsal and ventral divisions of the ventral nucleus of LL; the dorsal and intermediate nuclei of LL; the central nucleus, external nucleus and dorsal cortex of the IC outside the injection site; and small projections from central gray and the medial geniculate body.
Injections of retrograde fluorescent tracers into R showed strong labeling of the main, ventral nucleus of the medial geniculate (MGv).
The MGB sample was obtained mainly from recording sites located in two nuclei that project to AI, the ventral nucleus (VN, n = 118) and the lateral part of the posterior group of thalamic nuclei (Po, n = 84).
Fibers from the ventral nucleus terminated mainly in layer IV and deep portion of layer III (IIIB), with additional terminations in layers I-IIIA and in layer VI.
The ventral nucleus has a high density of parvalbumin cells and few calbindin cells, and the anterodorsal nucleus has a high density of parvalbumin cells and moderate numbers of calbindin cells. Parvalbumin cells in the ventral nucleus project to a central core of auditory cortex with densest parvalbumin immunoreactivity.
Extra- and intracellular synaptic responses were recorded by sharp electrode and whole-cell patch clamp techniques in the ventral nucleus of the medial geniculate body after electrical stimulation of the brachium of the inferior colliculus.
The ventral nucleus is strongly PV+ due to dense neuropil labeling and moderately labeled somata.
Observations were largely restricted to cells located within the tonotopically organized divisions of the MGB (i.e., the ventral nucleus and the lateral division of the posterior nuclear group) and the middle layers of AI.
The present study shows an increase NADPH-d histochemical staining in the optic layers of the superior colliculus, the ventral nucleus of the lateral geniculate body and the primary visual cortex in the rat after transection of the contralateral optic nerve.
By contrast, small boutons were found densely in the pars lateralis and pars ovoidea of the ventral nucleus, and to a lesser extent in the medial nucleus of MG. In the anterior third of the ventral nucleus, where the highest density of labeled fibers was observed, the small bouton terminations formed a plate-like plexus.
Injections into the somatosensory head/face and hindlimb/trunk areas of representation revealed a posteromedial ventral nucleus and a posterolateral ventral nucleus, respectively.
Although other auditory nuclei in the brain-stem, the ventral nucleus of the lateral lemniscus, the trapezoid body and the auditory nerve responded to transient stimuli with an amplitude larger than that of the IC, no amplification occurred with 50 Hz stimuli in these nuclei.
Senile plaques (SP) and neurofibrillary tangles (NFT) were distributed throughout the ventral nucleus of the medial geniculate body (MGB) and the central nucleus of the inferior colliculus (IC) in nine of nine AD patients. The ventral nucleus of the MGB is the major thalamic relay station for auditory function and receives fibers from neurons of the central nucleus of the IC, with projections arranged tonotopically in a laminar pattern corresponding to a gradient of high-to-low frequency ranges.
Injections involving neurons in the intergeniculate leaflet or the medial subpart of the ventral nucleus (which presumably is part of the intergeniculate leaflet of the thalamus too) gave rise to labeled nerve fibers in the opposite lateral geniculate nucleus. However, the dense innervation of the contralateral intergeniculate leaflet not only covered the small zone between the dorsal and ventral nuclei, but also a dorsomedial part of the ventral nucleus that merged caudally with the lateral part of the zona incerta. In the remaining part of the ventral nucleus, single Phaseolus vulgaris-leucoagglutinin-labeled fibers surrounded specific cells.
Most cells in the intermediate nucleus and the columnar division of the ventral nucleus of the lateral lemniscus were cabp(+).
Global functional interpretations of these nuclei as sites of visuoacoustic and somatoacoustic polymodal integration support the notion of a shell region of the medial geniculate, surrounding the principal cochleotopic ventral nucleus and interconnected to the cortical acoustic belt around the primary auditory area.
Neurons containing one or other of these proteins were present in most (but not all) regions of the complex and were differentially distributed; parvalbumin immunoreactive neurons tended to form densely packed clusters in the ventral nucleus and rather loose arrangements in the anterodorsal and posterodorsal nuclei, whereas most calbindin neurons were scattered, with concentrations in the caudal end of the posterodorsal and in the magnocellular nuclei.
The ventral nucleus of the medial geniculate body of the thalamus also displays prominent, and transient, staining for AChE.
The neurons in ventral nucleus of the medial geniculate body (MGv) respond vigorously to pure tones; they have mostly narrow frequency tuning curves and short response latencies (8-12 ms).
Reciprocal connections of the hypothalamus with the ventral nucleus of the lateral geniculate body and ventrolateral (subthalamic) nucleus were demonstrated in the lizard Ophisaurus apodus using the retrograde and anterograde axonal tracing method following local HRP injection into the mamillary complex..
The ventral nucleus (MGV) was only slightly labeled in its caudal division.
On P3 and P4, 30 h after tracer was deposited in the cortex, The HRP reaction product was observed in the dorsal nucleus of the lateral geniculate body and in the lateral posterior nucleus of the thalamus, but no labeled axons were observed in the ventral nucleus of the lateral geniculate body (LGBv) until P5.
In the ventral nucleus, this arrangement approximates vertical with a dorsomedial tilt most prominent rostrally; in the ovoid nucleus, tufted cells adhere to the double spiraled course of afferent axons.
ventral nucleus cells align with afferent brachial axons, which penetrate the nucleus in a dorsoventral direction, whereas rostrocaudal cellular arrays are retrogradely labeled after injections of horseradish peroxidase (HRP) into auditory cortex.
The main mass of the labeled thalamic cells was found in the ventral nucleus of the medial geniculate body (MGv).
These injections labeled a group of large multipolar cells lying between the ventral nucleus of the lateral lemniscus and the superior olivary complex.
The anterior field A receives its main thalamic input from the ventral nucleus of the MG (MGv).
In the opossum, the ventral division consists chiefly of the ventral nucleus. The ventral nucleus is divided into two main parts: the pars lateralis and the pars ovoidea, the former being relatively smaller in the opossum. The ventral nucleus of both species contains large principal neurons with bushy, tufted dendrites and smaller Golgi type II cells.
In agreement with previous reports we found abnormal projections in the ventral nucleus of the lateral geniculate body (LGv), in the lateral posterior nucleus (LP) of the thalamus, and in the left SC (the 'recrossing' pathway).
the neurones of the central nucleus of the inferior colliculus terminate in the ventral nucleus of the medial geniculate body.
Pentobarbital, and especially pentobarbital plus ketamine, enhanced stimulus-evoked increases in relative 2-DG uptake in lower auditory nuclei: the cochlear nuclei, superior olivary complex and ventral nucleus of the lateral lemniscus.
The percentage of neurons that are immunoreactive for the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA) was determined within: (1) the lateral geniculate nucleus (LGN), (2) the ventrobasal complex (VB) and (3) the antero-ventral nucleus (AV) of the thalamus in the cat.
Degenerative debris can be observed in the ventral and dorsal nuclei at postnatal days 2-10 and is present in greater and more variable amounts in the ventral nucleus.
The ventral nucleus is physiologically characterized as a region containing narrowly tuned, short-latency (less than or equal to 40 ms) responses and an orderly tonotopic organization. Best frequencies were plotted as a function of depth along single electrode penetrations, and the sequences from different locations in the ventral nucleus were compared. We divided the ventral nucleus into seven different rostrocaudal levels, each characterized by a different pattern of tonotopy. At middle levels, low- and mid-frequency contours course ventromedially from the dorsal border of the ventral nucleus toward its medial border, then turn sharply and continue ventrolaterally. A model of the three-dimensional tonotopic organization of the ventral nucleus is described that is consistent with the two-dimensional best-frequency maps obtained at different rostrocaudal levels and with locations of ventral nucleus neurons labeled by horseradish peroxidase injections into low-, mid-, and high-frequency representations in auditory cortex.
The topographic distribution of projections from the ventral nucleus of the lateral lemniscus (VNLL) in the cat was investigated with the autoradiographic tracing method. The descending projection ended mainly in the dorsomedial periolivary region and ventral nucleus of the trapezoid body.
The neuronal types in the ventral nucleus of the cat medial geniculate body projecting to the primary auditory cortex (AI) were investigated using the retrograde transport of horseradish peroxidase. After large injections, more than 90% of the neurons in the ventral nucleus, the principal nucleus of the lemniscal auditory pathway, were labeled, and the population of labeled cells included both large and small neuronal somata. Since the ventral nucleus contains only two varieties of cells--large neurons with bushy dendrites and an unbranched axon, and smaller cells with thin dendrites and a locally projecting axon--it is concluded that at least some of the small cells, previously believed to be interneurons, may function both as local circuit and as projection neurons. Besides the small, labeled neurons in the ventral nucleus, many labeled cells were seen in the interstitial nucleus of the brachium of the inferior colliculus. Thus, in addition to the route embodied by the large bushy neurons which project to primary auditory cortex, at least one other pathway--represented by certain of the small cells in the ventral nucleus, reaches the primary auditory cortex..
Thus, the ventral nucleus had long fascicles of axons running parallel to the dendrites of bushy neurons, while the marginal and ovoid nuclei had a different organization.
The HRP cytoarchitecture of the three divisions is described, and the portions of the ventral division corresponding with the physiologically and cytoarchitectonically defined ventral nucleus are identified. The topographic organizations of the ventral division (and its tonotopic subdivision, the ventral nucleus), the lateral posterior complex (also tonotopically organized), and the medial division are described. There are planar and concentric components of the topographic organization in the ventral nucleus. In the lateral posterior complex, the low-frequency area is located rostrally, and the high-frequency area is located caudally adjoining the high-frequency area in the ventral nucleus. The topographic organizations of the ventral nucleus and lateral posterior complex are consistent with tonotopic maps of these regions. The medium- and large-cell portion of the medial division is also topographically organized, although there may be more overlap among low-, middle-, and high-frequency arrays than in the ventral nucleus.(ABSTRACT TRUNCATED AT 400 WORDS).
Ultrastructure of the synapses in the ventral nucleus of the cat medial geniculate body was examined with freeze-fracture and thin section techniques.
The auditory input from the central nucleus of the inferior colliculus tends to project more heavily to the caudolateral region next to the ventral nucleus of the medial geniculate body.
These functional differences may correlate with the relative morphological homogeneity of the ventral nucleus compared to the extremely heterogeneous medial division. A comparison of the structure, connections, and function of the medial geniculate body suggests that the dorsal division is predominantly, but probably not exclusively auditory, while the ventral nucleus is entirely auditory and relatively homogeneous, and the medial division, polymodal and heterogeneous with respect to input..
The lateral fasciculus branches from the main optic tract at the level of the ventral nucleus of the lateral geniculate body and descends the lateral surface of the crus cerebri to enter the medial terminal nucleus after contributing a few fibers to the lateral terminal nucleus.
Connection of a posteromedial region of the ventral nucleus of the lateral lemniscus were examined in the cat using the autoradiographic tracing method. The autoradiographic findings revealed that many axons from the posteromedial region of the ventral nucleus of the lateral lemniscus that entered the superior colliculus continued into the midbrain reticular formation. Other sub-collicular regions also contained labeled cells in these cases, including the main body of the ventral nucleus of the lateral lemniscus and scattered cell groups around the superior olivary complex..
The ventral nucleus contains tufted cells with disc-shaped dendritic fields which are aligned to form laminae. The ventral nucleus is the medial geniculate component of the central pathway which extends from the central nucleus of the inferior colliculus to the primary auditory cortex.
Volumetric investigations of the dorsal and ventral nucleus of the lateral geniculate body (dLGN and vLGN) in 16 mammalian species showed that forms with a high level of neocorticalization are characterized by a high quotient of dLGN and vLGN volumina.
At 14 DAB, 2-DG uptake increased during WBN in the entire cochlear nuclear complex, superior olivary complex, and ventral nucleus of the lateral lemniscus.
Additional thalamic components were traced to specific sites within the "posterior group," including a medial component largely traversed by lemniscal axons and a caudolateral component lying between the principal nucleus of the medial geniculate and ventral nucleus of the lateral geniculate.
A third, more modest, pathway originates chiefly in the middle M and D, with a minor contribution from S and cell group y, and terminates in the contralateral ventral nucleus of the lateral geniculate body (GLV).
Auditory structures: inferior colliculus (external and pericentral nuclei), dorsomedial periolivary nucleus, nuclei of the trapezoid body, ventral nucleus of the lateral lemniscus.
The other labelled structures were the prepositus hypoglossi complex (PH), the ventral nucleus of the lateral geniculate body (LGV), the locus coeruleus, the cuneiform nucleus, the periaqueductal gray and the dorsomedial hypothalamic area.
The primary auditory cortex receives projections from the ventral nucleus.
The ventral division of the medial geniculate body contains at least two subdivisions, the ventral nucleus and the caudomarginal nucleus. The ventral nucleus is characterized by densely-packed cells and receives topographically organized projections from the central nucleus of the inferior colliculus.
The ventral nucleus is developing earlier than the dorsal nucleus.
Abundant degeneration passed into the contralateral lateral lemniscus and was distributed largely to its ventral nucleus. The caudal tip of the ipsilateral ventral nucleus of the lateral lemniscus received abundant degeneration, but this diminished rostrally.
Extracellular unitary recordings were made from 125 neurons, of which 91 were LGd neurons, 23 neurons of the caudal part of the thalamic reticular nucleus (TRc) and 11 neurons of the ventral nucleus of LG (LGv).
The end of neurogenesis in the LGB, especially in the ventral nucleus, coincided with the time of neurogenesis in the deep cortical layers.
The ventral nucleus of the lateral geniculate body had 5 major projections to brain stem structures both ipsilateral and contralateral to the injected nucleus.
A combined analysis with the Golgi and silver-degeneration methods and electron microscopy in the ventral nucleus of the medial geniculate body has confirmed that the Golgi type II neuron forms dendro-dendritic synapses with the principal neuron in terminal aggregates called synaptic nests.
and end in the pars lateralis of the ventral nucleus of the MGB, Arising from AII, axons pass through the magnocellular MGB and end in the superficial and deep subdivisions of the dorsal nucleus extending to the most caudal part of the MGB.
The ventral cochlear nucleus (VCN) projects via the trapezoid body to ipsilateral LSO, ipsilateral preolivary nuclei, ipsilateral lateral and a contralateral medial dendritic fields of MSO, and contralateral NTB; there is also a small ipsilateral projection to the ventral nucleus of the lateral lemniscus (VNLL) and the central nucleus of the inferior colliculus (CNIC).
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