Medial Geniculate Body Of Cat Research Articles

GABAergic organization of the cat medial geniculate body

GABAergic organization of the cat medial geniculate body

GABAergic organization of the cat medial geniculate body

A study of neurons and processes (puncta) immunolabeled by antibodies to gamma-aminobutyric acid (GABA) or glutamic acid decarboxylase was undertaken in the medial geniculate body of the adult cat. The proportion and types of GABAergic cells were determined with high resolution methods, including postembbedding immunocytochemistry on semithin plastic sections. A second goal was to draw parallels and differences between the auditory thalamus and other thalamic nuclei. Finally, the types of GABAergic puncta and their concentration in the three major subdivisions of the medial geniculate body were analyzed. The results were that (1) each division had many GABAergic neurons, averaging approximately 26% of the neuronal population; (2) the ventral division had the highest proportion of these cells (33%), the medial division the fewest (18%), and the dorsal division was intermediate (26%); (3) there was a gradient in the proportion of GABAergic neurons, i.e., the ventral and medial division values increased caudorostrally, whereas the value in the dorsal division declined; (4) the predominant GABAergic cell type in each division was a small neuron with a soma approximately 10-12 microm in diameter; (5) a small population of much larger GABAergic neurons was present mainly in the dorsal division; (6) in addition to the fine, granular puncta in each division, a type of giant GABAergic puncta was found only in the dorsal division nuclei. The results obtained with the two antibodies were essentially identical. These findings suggest a structural basis for qualitative differences in the distribution of GABAergic processing within the medial geniculate complex. The GABAergic arrangement in the ventral division was stereotyped, with only one type of putative GABAergic interneuron, and the puncta were correspondingly homogeneous. In contrast, the dorsal division had two types of GABAergic neurons, and the giant GABAergic puncta represent a new substrate for inhibitory interactions. The medial division also had more than one type of GABAergic neuron and a slightly lower concentration of puncta. These qualitative and quantitative distinctions suggest a morphologic basis for possible differences in inhibitory processing among medial geniculate body subdivisions.

Two systems of giant axon terminals in the cat medial geniculate body: Convergence of cortical and GABAergic inputs

The thalamus plays a critical role in processing sensory information that involves interactions between extrinsic connections and intrinsic circuitry. Little is known regarding how these different systems might interact. We found an unexpected nuclear convergence of two types of giant axon terminals, each of which must have independent origins, in the dorsal division of the cat medial geniculate body. The first class of giant terminal was labeled after injections of biotinylated dextran amines (BDA) in seven auditory cortical areas. A second type was found in sections immunostained for gamma-aminobutyric acid (GABA); these endings had the same nuclear distribution, and they were numerous. The origin of this GABAergic terminal is unknown. The giant corticothalamic terminals were presumably those described in prior accounts using different tracers (Rouiller and de Ribaupierre [1990] Neurosci. Lett. 208:29-35; Ojima [1994] Cerebral Cortex 6:646-663), but with BDA they are labeled more fully. Clusters of such endings were often linked, and hundreds may occur in a single section. Their boutons formed a substantial proportion of the corticothalamic population. Other types of corticogeniculate axon terminals were also labeled, including two kinds that are much smaller and that match closely the classical descriptions of corticothalamic axons. The giant GABAergic endings were found in all dorsal division nuclei and in thalamic visual nuclei such as the lateral posterior nucleus. Like the giant cortical endings, the giant GABAergic terminals often encircled large, pale, immunonegative profiles that may be dendritic. This implies a close spatial, and perhaps a close functional, relationship between the populations of giant axon terminals. Insofar as physiological studies found that pharmacological inactivation of rat somatic sensory cortex suppresses peripheral information transmission through the posterior thalamus, corticofugal input may be essential for normal processing (Diamond et al. [1992] J. Comp. Neurol. 319:66-84). Our findings suggest that the giant corticothalamic endings could play an important role in descending control. Perhaps they are counterbalanced by a GABAergic system and affect thalamic oscillations implicated in shifts in vigilance and attention.

Two systems of giant axon terminals in the cat medial geniculate body: Convergence of cortical and GABAergic inputs

The thalamus plays a critical role in processing sensory information that involves interactions between extrinsic connections and intrinsic circuitry. Little is known regarding how these different systems might interact. We found an unexpected nuclear convergence of two types of giant axon terminals, each of which must have independent origins, in the dorsal division of the cat medial geniculate body. The first class of giant terminal was labeled after injections of biotinylated dextran amines (BDA) in seven auditory cortical areas. A second type was found in sections immunostained for γ-aminobutyric acid (GABA); these endings had the same nuclear distribution, and they were numerous. The origin of this GABAergic terminal is unknown. The giant corticothalamic terminals were presumably those described in prior accounts using different tracers (Rouiller and de Ribaupierre [1990] Neurosci. Lett. 208:29–35; Ojima [1994] Cerebral Cortex 6:646–663), but with BDA they are labeled more fully. Clusters of such endings were often linked, and hundreds may occur in a single section. Their boutons formed a substantial proportion of the corticothalamic population. Other types of corticogeniculate axon terminals were also labeled, including two kinds that are much smaller and that match closely the classical descriptions of corticothalamic axons. The giant GABAergic endings were found in all dorsal division nuclei and in thalamic visual nuclei such as the lateral posterior nucleus. Like the giant cortical endings, the giant GABAergic terminals often encircled large, pale, immunonegative profiles that may be dendritic. This implies a close spatial, and perhaps a close functional, relationship between the populations of giant axon terminals. Insofar as physiological studies found that pharmacological inactivation of rat somatic sensory cortex suppresses peripheral information transmission through the posterior thalamus, corticofugal input may be essential for normal processing (Diamond et al. [1992] J. Comp. Neurol. 319:66–84). Our findings suggest that the giant corticothalamic endings could play an important role in descending control. Perhaps they are counterbalanced by a GABAergic system and affect thalamic oscillations implicated in shifts in vigilance and attention. J. Comp. Neurol. 413:181–197, 1999. © 1999 Wiley-Liss, Inc.

Steady-state responses from the cat auditory cortex

Responses to 350 ms trains of clicks with 10–100 Hz repetition rate were recorded from the auditory cortices of six cats. Click trains of 30–50 and 90–100 Hz elicited a clear steady-state response (SSR) in awake state. SSRs were small or absent below 30 Hz and in 60–70 Hz stimulus range. In slow wave sleep the optimal rate to elicit SSR shifted towards lower frequencies. 90 Hz SSR was largest in paradoxical sleep. SSRs were strongly suppressed by barbiturate anesthesia. The amplitude of the SSR from the medial geniculate body (MGB) in two cats gradually decreased from 20 to 100 Hz and was more resilient to barbiturate anesthesia than the cortical SSRs. Only low amplitude or no SSRs could be recorded from vertex, visual and association cortices and from the hippocampus in control recordings. The results suggest different generation mechanisms for SSRs recorded from cat auditory cortex and MGB. Human auditory SSRs resemble cat auditory cortical SSRs more than those recorded from cat MGB. The results imply that auditory SSRs in humans are generated in the cortex.

Note on the tonotopic organization in the cat medial geniculate body: influence of sampling of units.

The tonotopic organization observed in the present study for the pars lateralis (LV) of the medial geniculate body (MGB) in nitrous oxide anesthetized cats is generally consistent with that previously reported under barbiturate anesthesia. The present data, however, provide evidence for local deviations in characteristic frequency (CF) using appropriate sampling procedures of single units. Although the majority of pairs of units recorded simultaneously with the same microelectrode showed comparable CFs, a few pairs of such neighbouring units displayed CF disparities of up to 1.5 octaves. In addition, some units characterized by an elevated threshold had a CF deviating significantly from the general CF progression observed for the majority of units having low thresholds. This study points out the influence of the sampling procedure on the quality of the tonotopic organization observed in the MGB in addition to a possible effect of the level of anesthesia.

A cytoarchitectonic atlas of the medial geniculate body of the opossum, Didelphys virginiana, with a comment on the posterior intralaminar nuclei of the thalamus

The organization of the medial geniculate body and adjacent posterior thalamus of the Virginia opossum was studied in Nissl-, Golgi-, reduced silver, and myelin-stained preparations. Our chief goals were to define the cytoarchitectonic subdivisions and boundaries in Nissl preparations and to reconcile these with those observed with the Golgi method and in experimental material, to present these results in an atlas of Nissl-stained sections, and to compare the chief nuclear groups in the opossum and the cat medial geniculate body. 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. However, the opossum has far fewer Golgi type II cells, and the texture of the neuropil is correspondingly different, although the primary ascending input from the midbrain arises from the central nucleus of the inferior colliculus in both species. The dorsal division consists of the dorsal nuclei, including the suprageniculate nucleus and the caudal part of the lateral posterior nucleus, the marginal zone, and the posterior limitans nucleus. These nuclei are identified in both species, although they are much smaller in the opossum. The neurons consist of medium-size and small somata with a predominantly radiate mode of dendritic branching and a lower cell concentration than in the ventral division. In both species the afferent brain stem input comes from the inferior colliculus, the lateral tegmental area, the intercollicular tegmentum, and the superior colliculus. The medial division contains several types of cells, which are heterogeneous in form and size, most having radiating dendrites and a low cellular concentration. This division is especially smaller in the opossum, although comparable inputs arise from various auditory and non-auditory sources in the midbrain and spinal cord in both species. A large intralaminar complex of nuclei occurs in the opossum, which have a more extensive distribution than previously appreciated. They not only occupy the intramedullary laminae but form a shell around the medial geniculate nuclei and adjoining main sensory nuclei. The intralaminar complex includes the posterior limitans, posterior intralaminar, posterior, parafascicular, posterior parafascicular, central intralaminar, limitans, and central medial nuclei, and the marginal zone of the medial geniculate body.(ABSTRACT TRUNCATED AT 400 WORDS)

Patterns of reciprocity in auditory thalamocortical and corticothalamic connections: study with horseradish peroxidase and autoradiographic methods in the rat medial geniculate body.

The patterns of reciprocity between retrogradely labeled thalamocortical cells of origin and anterogradely projecting corticothalamic axon terminals were studied in the subdivisions of the adult rat medial geniculate body following auditory cortical injections of mixtures of horseradish peroxidase and [3H]leucine. The labeling produced by each method was examined independently, both qualitatively and quantitatively, in adjacent series of tetramethylbenzidine-processed sections and in autoradiographs after 24-96 hour survivals. The distribution and number of labeled cells and axon terminals were assessed separately for each method and compared systematically throughout the rostro-caudal extent of the medial geniculate complex. The principal finding was that zones containing many retrogradely labeled neuronal somata are not completely coextensive with areas of heavy terminal labeling within the medial geniculate body, although there is a gross congruence of thalamocortical-corticothalamic projections. Conversely, we found many zones of autoradiographic silver grains without retrogradely labeled somata in the adjacent sections; in general, the autoradiographic zones of non-reciprocity were more extensive and marked than were retrograde zones of non-reciprocity. The rat medial geniculate complex could be subdivided on the basis of its neuronal organization, cytoarchitecture, fiber architecture, and thalamocortical and corticothalamic connections into three major parts: the ventral, dorsal, and medial divisions. This pattern of organization was comparable, though not identical, to that of the corresponding subdivisions in the cat medial geniculate body (Winer: Adv. Anat. Embryol. Cell Biol. 86:1-98, '85). While the retrograde labeling appeared to mark many of the different types of neurons in each of the three divisions, there were distinct local and quantitative and qualitative differences in the distribution of autoradiographic terminal labeling. The ventral division received the heaviest cortical input, the medial division the least labeling, while the dorsal division was intermediate. Thus, corticogeniculate projections to the ventral division often produced values 20-100 times above background (absolute values: 2,001-10,000 silver grains/14,400 micron2; background: less than 100 silver grains/14,400 micron2); the same projection to the dorsal division usually resulted in grain counts no more than 5-20 times above background (501-2,000/14,400 micron2), while in the medial division the number of silver grains rarely exceeded two to five times the background (201-500/14,400 micron2).(ABSTRACT TRUNCATED AT 400 WORDS)

Identification and structure of neurons in the medial geniculate body projecting to primary auditory cortex (AI) in the cat

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. These cells were compared with the morphology of neurons as revealed in Golgi and Nissl preparations, plastic-embedded tissue, and electron microscopic material. 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. These findings were confirmed in toluidine blue-stained, 1–2 μm thick sections, and in the electron microscope, where small cells with sparse cytoplasm and a deeply invaginated nuclear envelope often contained intracellular horseradish peroxidase granules, as well as the larger 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. This hitherto poorly characterized group of cells is embedded among the fibers of the brachium of the inferior colliculus. Many of the morphologically distinct varieties of cells in the medial division of the medial geniculate body, including small neurons, were labeled. 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.

Afferent fibers to the anterior suprasylvian gyrus from the medial geniculate body of cat

Afferents to the anterior suprasylvian gyrus (ASG) from the medial geniculate body of cat were demonstrated by means of autoradiography. [ 3H]Glycine was injected stereotactically into the medial division of the medial geniculate body (mMGB). After a 3-day survival period, the auditory cortices and the ASG were excised. Labelled terminals were found in the ASG, in the anterior auditory field (AAF) and in the acoustic cortex (AI). The density of labelling was highest in the ASG and lower in the AAF and AI. The afferents from the mMGB made synaptic contacts in the 3rd layer of the cortices examined.

Intensity functions of single unit responses to tone in the medial geniculate body of cat.

Extracellular spike activity was recorded from single units in the medial geniculate body (MGB) of nitrous oxide anaesthetized cats. The responses of 291 units to tone bursts at the characteristic frequency (CF) were studied as a function of stimulus intensity, covering a range from 10 to 100 dB SPL. The proportion of MGB units characterized by a monotonic or a non-monotonic discharge rate--intensity function was 26% and 74%, respectively. In addition, changes of response latency as a function of tone levels were demonstrated to be either monotonic (38% of units) or non-monotonic (62% of units). One third Of MGB units showed a change of response pattern with increasing intensities, in similar proportion towards either prevailing excitatory or inhibitory components. The monotonic units tended to differ from non-monotonic ones in addition to their intensity function by showing shorter response latencies, a higher response probability to broad-band stimuli and simpler response patterns. The mean dynamic range of the monotonic unit population was 60 dB, with thresholds ranging from 10 to 90 dB SPL; most discharge rate--intensity functions did not saturate at sound levels of 100 dB SPL. In the population of non-monotonic units, the 'best' intensity, defined as th intensity giving the strongest response, ranged between 10 and 100 dB SPL. The present results suggest that the intensity could be signaled by the mean firing rate of a restricted population of monotonic units or place coded by the distribution of maximally activated non-monotonic units which are broadly tuned to different intensities.

Intrinsic organization of the cat's medial geniculate body identified by projections to binaural response-specific bands in the primary auditory cortex

The area of the cat's primary auditory cortex (AI) within which high frequency sounds are represented can be subdivided using functional criteria. Within each subdivision, or "binaural interaction band," all recorded neurons display similar responses to binaural stimulation. The current study distinguishes the thalamic sources of input to these subdivisions of AI and characterizes the topography within the thalamic projection to each class of bands. The borders of binaural bands in AI were mapped using microelectrode recording with diotic tonal stimulation, then injections of one to three retrograde tracers were introduced into identified bands. Within the ventral division (V) of the medial geniculate body (the major thalamic source of input to AI), the neuronal populations that projected to different classes of binaural bands were strictly segregated from each other. This segregation of class-specific thalamic sources constitutes a laminar organization within an axis of V that is orthogonal to the previously described tonotopic organization. Excitatory/excitatory (EE) binaural neurons in AI were found to be segregated from excitatory/inhibitory (EI) neurons in alternating "bands." We consistently identified: (1) a ventral pair of rostrocaudally continuous EI and EE bands, (2) a middle area within which the pattern of binaural subdivisions was more variable and within which bands often were discontinuous rostrocaudally, and (3) a dorsal zone (DZ) within which the responses of neurons differed in binaural properties and in frequency specificity from the response patterns that were characteristic of neurons elsewhere in AI. Each EI band apparently derived input that converged from three thickened laminae of cells in V that were oriented approximately horizontally. The most ventral of these laminae encompassed the ovoidal part of V (Vo), suggesting that EI bands are the only recipients in AI of a projection from Vo. All of the EE bands and DZ derived their input from a single continuous structure which included the dorsal two-thirds of the rostral pole of V and a horizontal lamina interposed between the two dorsalmost EI-projecting laminae. Restricted portions of the complex EE-projecting structure in V projected preferentially to particular EE subdivisions of AI. The V-to-AI thalamocortical topography exhibited a high degree of convergence and divergence within the projections to each cortical binaural band and within the projections to each class of bands. These observations indicate that the high frequency representation in AI and its principal thalamic source of input, the ventral division of the medial geniculate body, may be thought of as assemblies of spatially discrete, functionally distinguishable subunits. The significance of this intrinsic organization is discussed in regard to the requirements for analysis of sound stimuli.

Neural coding of repetitive clicks in the medial geniculate body of cat.

The activity of 418 medial geniculate body (MGB) units was studied in response to repetitive acoustic pulses in 35 nitrous oxide anaesthetized cats. The proportion of MGB neurons insensitive to repetitive clicks was close to 30%. On the basis of their pattern of discharge, the responsive units were divided into three categories. The majority of them (71%), classified as "lockers', showed discharges precisely time-locked to the individual clicks of the train. A few units (8%), called "groupers', had discharges loosely synchronized to low-rate repetitive clicks. When the spikes were not synchronized, the cell had transient or sustained responses for a limited frequency range and was classified as a "special responder' (21%). Responses of "lockers' were time-locked up to a limiting rate, which varied between 10 and 800 Hz; half of the "lockers' had a limiting rate of locking equal to or higher than 100 Hz. The degree of entrainment, defined as the probability that each click evokes at least one spike, regularly decreases for increasing rates; on the other hand, the precision of locking increasing increases with frequency. The time jitter observed at 100 Hz might be as small as 0.2 ms and was 1.2 ms on average. The population of "lockers' can mark with precision the transients of complex sounds and has response properties still compatible with a temporal coding of the fundamental frequency of most animal vocalizations.

Auditory representation within principal division of cat medial geniculate body: an electrophysiology study.

Auditory representation within principal division of cat medial geniculate body: an electrophysiology study.M B Calford, and W R WebsterM B Calford, and W R WebsterPublished Online:01 Jun 1981https://doi.org/10.1152/jn.1981.45.6.1013MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByNoise-induced neurophysiological alterations in the rat medial geniculate body and thalamocortical desynchronization by deep brain stimulationGusta van Zwieten, Mark J. Roberts, Frédéric L. V. W Schaper, Jasper V. Smit, Yasin Temel, and Marcus L. F. Janssen25 February 2021 | Journal of Neurophysiology, Vol. 125, No. 2Septal and Hippocampal Neurons Contribute to Auditory Relay and Fear Conditioning16 April 2018 | Frontiers in Cellular Neuroscience, Vol. 12Neuronal activation times to simple, complex, and natural sounds in cat primary and nonprimary auditory cortexAndres Carrasco, and Stephen G. Lomber1 September 2011 | Journal of Neurophysiology, Vol. 106, No. 3Binaural sensitivity changes between cortical on and off responsesDouglas E. H. Hartley, Johannes C. Dahmen, Andrew J. King, and Jan W. H. Schnupp1 July 2011 | Journal of Neurophysiology, Vol. 106, No. 1Adaptive Stimulus Optimization for Auditory Cortical NeuronsKevin N. O'Connor, Christopher I. Petkov, and Mitchell L. Sutter1 December 2005 | Journal of Neurophysiology, Vol. 94, No. 6Masking and scrambling in the auditory thalamus of awake rats by Gaussian and modulated noises27 September 2004 | Proceedings of the National Academy of Sciences, Vol. 101, No. 41In vivo intracellular responses of the medial geniculate neurones to acoustic stimuli in anaesthetized guinea pigs5 October 2004 | The Journal of Physiology, Vol. 560, No. 1Cortical mapping of auditory-evoked offset responses in ratsNeuroReport, Vol. 15, No. 10Intracortical Pathways Determine Breadth of Subthreshold Frequency Receptive Fields in Primary Auditory CortexSimranjit Kaur, Ronit Lazar, and Raju Metherate1 June 2004 | Journal of Neurophysiology, Vol. 91, No. 6Redefining the tonotopic core of rat auditory cortex: Physiological evidence for a posterior field18 October 2002 | The Journal of Comparative Neurology, Vol. 453, No. 4off Responses in the Auditory Thalamus of the Guinea PigJufang He1 November 2002 | Journal of Neurophysiology, Vol. 88, No. 5Neural Basis of Audition15 July 2002Spectrotemporal Receptive Fields in the Lemniscal Auditory Thalamus and CortexLee M. Miller, Monty A. Escabí, Heather L. Read, and Christoph E. Schreiner1 January 2002 | Journal of Neurophysiology, Vol. 87, No. 1Frequency Organization and Responses to Complex Sounds in the Medial Geniculate Body of the Mustached BatJeffrey J. Wenstrup1 November 1999 | Journal of Neurophysiology, Vol. 82, No. 5Anatomic, Intrinsic, and Synaptic Properties of Dorsal and Ventral Division Neurons in Rat Medial Geniculate BodyEdward L. Bartlett, and Philip H. Smith1 May 1999 | Journal of Neurophysiology, Vol. 81, No. 5Response properties of single units in areas of rat auditory thalamus that project to the amygdalaExperimental Brain Research, Vol. 98, No. 2Binaural response patterns in subdivisions of the medial geniculate bodyBrain Research, Vol. 640, No. 1-2Audition and the auditory pathway of a vocal new world primate, the common marmosetProgress in Neurobiology, Vol. 41, No. 3Frequency selectivity is related to temporal processing in parallel thalamocortical auditory pathwaysBrain Research, Vol. 583, No. 1-2Frequency-specific plasticity of single unit discharges in the rat medial geniculate bodyBrain Research, Vol. 529, No. 1-2The descending auditory pathway and acousticomotor systems: connections with the inferior colliculusBrain Research Reviews, Vol. 15, No. 3Functional organization of the ventral division of the medial geniculate body of the cat: Evidence for a rostro-caudal gradient of response properties and cortical projectionsHearing Research, Vol. 39, No. 1-2Involvement of cortical and thalamic auditory regions in retention of differential bradycardiac conditioning to acoustic conditioned stimuli in rabbitsBrain Research, Vol. 412, No. 2Physiological plasticity in auditory cortex: Rapid induction by learningProgress in Neurobiology, Vol. 29, No. 1Origin of afferents to physiologically defined regions of the medial geniculate body of the cat: ventral and dorsal divisionsHearing Research, Vol. 19, No. 2Afferent projections to the nucleus cuneiformis in the ratNeuroscience Letters, Vol. 52, No. 1-2The human medial geniculate bodyHearing Research, Vol. 15, No. 3Measurement of frequency selectivity of single neurons in the central auditory pathwayHearing Research, Vol. 11, No. 3Properties of single neurons in the anterior auditory field (AAF) of cat cerebral cortexBrain Research, Vol. 248, No. 2A combined electrophysiological and [14C]2-deoxyglucose study of the frequency organization of the inferior colliculus of the catNeuroscience Letters, Vol. 27, No. 2 More from this issue > Volume 45Issue 6June 1981Pages 1013-28 https://doi.org/10.1152/jn.1981.45.6.1013PubMed7252528History Published online 1 June 1981 Published in print 1 June 1981 Metrics

Organization of protection from the central nucleus of the inferior colliculus into the medial geniculate body of cat

Orthograde tracer experiments were conducted to define, in detail, projections of the central nucleus of the inferior colliculus (ICC) into the medial geniculate body (MGB). Injections of 3H-1-leucine were introduced at physiologically defined loci within the ICC. The bilateral and spacially symmetrical projection was less dense to the contralateral MGB. The projection into the MGB formed a medial column passing rostrocaudally through the medial and deep dorsal nuclei; and formed a more lateral sheet passing rostrocaudally within the ventral nucleus and continuous through the lateral, transitional, and ovoidal subdivisions of the nucleus. Projections were topographically ordered within all labeled subdivisions of MGB. Bands of periodic light and heavy labeling were often seen approximately normal to the morphological laminations of the lateral division of the ventral nucleus. The basic pattern and topographic (cochleotopic) organization of the ICC projection into the MGB was indistinguishable from the pattern and topographic (cochleotopic) organization of the thalamocortical and corticothalamic projections. [Supported by NIH grant NS-10414 and Hearing Research Inc.]

Tone-burst response patterns of single units in the cat medial geniculate body

One hundred and eighty nine medial geniculate body (MGB) units were studied in barbiturate anesthetized cats during binaural tone-burst stimulation. The data from these units were analyzed and response histograms were produced for the various units under different stimulus conditions. Many different types of MGB response patterns were evoked by binaural tone-burst stimuli. These types were broadly classified into those units initially excited (onset excitation units) and those initially inhibited (onset inhibition units) by the stimulus. Certain features of these response patterns were found to vary systematically with systematic changes in stimulus parameters. Sixteen units were unaffected by binaural tone stimulation.

Inhibition in the medial geniculate body of the cat.

1. Inhibitory activity in the cat medial geniculate body (MG) was examined by stimulating electrically and acoustically the input and output of the MG. 2. A longer and more profound depression of excitability occurs following a click-evoked potential in the MG than in the inferior colliculus (IC) in both anesthetized and unanesthetized states. Recovery is cyclic in the barbiturate MG preparation. 3. Electrical stimulation of the brachium of the inferior colliculus (BIG) evokes a field potential in the MG consisting of clearly distinguishable presynaptic and postsynaptic components. The presynaptic component recovers rapidly, while the postsynaptic component requires 100–200 msec for full recovery. This depression of excitability is localized within the MG since cortical ablation does not alter its occurrence. 4. Stimulation of the BIC mimics the effects of click stimulation on single units. Excitatory, inhibitory and reverberatory responses are evoked by the BIC shock. Suppression of single unit activity correlates with the depression of excitability following a BIC-evoked field response. 5. Cortical stimulation can evoke antidromic and trans-synaptic unit responses in the MG, as well as causing a variety of inhibitory effects and reverberation. In view of the fact that cortical ablation does not impair the recording of these responses to afferent stimuli, it is suggested that the cortical-evoked responses are at least partly mediated by antidromic conduction to MG. 6. Evidence is presented that inhibitory effects of both afferent and cortical stimulation are due to active inhibition of MG unit activity. Speculations are made as to the mechanisms producing inhibition and reverberation in the MG.

Interplay of excitation and inhibition in the cat medial geniculate body.

Interplay of excitation and inhibition in the cat medial geniculate body.

Activity of neural units in medial geniculate body of cat and rabbit.

Activity of neural units in medial geniculate body of cat and rabbit.H O Adrian, W M Lifschitz, R J Tavitas, and F P GalliH O Adrian, W M Lifschitz, R J Tavitas, and F P GalliPublished Online:01 Nov 1966https://doi.org/10.1152/jn.1966.29.6.1046MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByDirectionality Derived From Differential Sensitivity to Monaural and Binaural Cues in the Cat's Medial Geniculate BodyFrank K. Samson, Pascal Barone, W. Andrew Irons, Janine C. Clarey, Pierre Poirier, and Thomas J. Imig1 September 2000 | Journal of Neurophysiology, Vol. 84, No. 3Binaural vs. monaural auditory evoked potentials in rat neocortexBrain Research, Vol. 630, No. 1-2Periodicity coding in the auditory systemHearing Research, Vol. 60, No. 2T complex hemispheric asymmetries: Effects of stimulus intensityHearing Research, Vol. 34, No. 3A rabbit preparation for neuro-behavioral auditory researchHearing Research, Vol. 2, No. 1Phase-locked responses to low frequency tones in the medial geniculate bodyHearing Research, Vol. 1, No. 3Effects of ethanol, caffeine, and placebo on the auditory evoked responseElectroencephalography and Clinical Neurophysiology, Vol. 44, No. 5Hemispheric differences in the auditory evoked responseElectroencephalography and Clinical Neurophysiology, Vol. 43, No. 1A temporal component of the auditory evoked responseElectroencephalography and Clinical Neurophysiology, Vol. 39, No. 6Sound localization: the role of the commissural pathways of the auditory system of the catBrain Research, Vol. 82, No. 1Binaural interaction in the inferior colliculus of the frogExperimental Neurology, Vol. 37, No. 3Auditory responses of units in the ovoid nucleus and cerebrum (Field L) of the ring doveBrain Research, Vol. 24, No. 2Tone-burst response patterns of single units in the cat medial geniculate bodyBrain Research, Vol. 16, No. 1Tone response patterns of the auditory nuclei during normal wakefulness, paralysis, and anesthesiaBrain Research, Vol. 15, No. 2Progressive alterations in cochlear nucleus, inferior colliculus, and medial geniculate responses during acoustic habituationExperimental Neurology, Vol. 25, No. 1Are there neurons detecting direction of sound source motion?Experimental Neurology, Vol. 22, No. 1 More from this issue > Volume 29Issue 6November 1966Pages 1046-60 https://doi.org/10.1152/jn.1966.29.6.1046PubMed5971661History Published online 1 November 1966 Published in print 1 November 1966 Metrics

Acetylcholinesterase and pseudocholinesterase in neural and non-neural tissue in the medial geniculate body of the cat

The technique of retrograde degeneration has shown that acetylcholine esterase is present in both pre- and post-synaptic neurons in the medial geniculate body of cat. In sensory systems the enzyme activity is higher in cell groups than in adjacent fiber tracts. Butyrylcholine esterase is probably present in glial and vascular tissue as well as in neural tissue of the medial geniculate body, and is higher in the fiber tracts of the central nervous system than in most of the adjacent cell groups.