Representation of the cochlea within the anterior auditory field (AAF) of the cat (original) (raw)
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Experimental Brain Research, 1991
The origin and laminar arrangement of the homolateral and callosal projections to the anterior (AAF), primary (AI), posterior (PAF) and secondary (AII) auditory cortical areas were studied in the cat by means of electrophysiological recording and WGA-HRP tracing techniques. The transcallosal projections to AAF, AI, PAF and AII were principally homotypic since the major source of input was their corresponding area in the contralateral cortex. Heterotypic transcallosal projections to AAF and AI were seen, originating from the contralateral AI and AAF, respectively. PAF received heterotypic commissural projections from the opposite ventroposterior auditory cortical field (VPAF). Heterotypic callosal inputs to AII were rare, originating from AAF and AI. The neurons of origin of the transcallosal connections were located mainly in layers II and III (70 92%), and less frequently in deep layers (V and VI, 8-30%). Single unit recordings provided evidence that both homotypic and heterotypic transcallosal projections connect corresponding frequency regions of the two Abbreviations: AAF = anterior auditory cortical area; AI = primary auditory cortical area; AII=secondary auditory cortical area; BF = best frequency; C = cerebral cortex; CA = caudate nucleus; CL=claustrum; D=dorsal nucleus of the dorsal division of the MGB; ea = anterior ectosylvian sulcus; ep = posterior ectosylvian sulcus; IC =internal capsule; LGN = lateral geniculate nucleus; LV = pars lateralis of the ventral division of the MGB ; LVe = lateral ventricule; M = pars magnocellularis of the medial division of the MGB; MGB = medial geniculate body; MGBv = ventral division of the MGB; OT = optic tract; OV = pars ovoidea of the ventral division of the MGB; PAF=posterior auditory cortical area; PH = parahippocampal cortex; PO =lateral part of the posterior group of thalamic nuclei; PU = putamen; RE = reticular complex of thalamus; rs = rhinal sulcus; SG = suprageniculate nucleus of the dorsal division of the MGB ; ss = suprasylvian sulcus; TMB = tetrametylbenzidine; VBX=ventrobasal complex; VLa=ventrolateral complex; VL = ventro-lateral nucleus of the ventral division of the MGB; WGA-HRP =wheat germ agglutinin conjugated to horseradish peroxidase; WM=white matter; VPAF=ventro-posterior auditory cortical area
Modular Functional Organization of Cat Anterior Auditory Field
Journal of Neurophysiology, 2004
Two tonotopic areas, the primary auditory cortex (AI) and the anterior auditory field (AAF), are the primary cortical fields in the cat auditory system. They receive largely independent, concurrent thalamocortical projections from the different thalamic divisions despite their hierarchical equivalency. The parallel streams of thalamic inputs to AAF and AI suggest that AAF neurons may differ from AI neurons in physiological properties. Although a modular functional organization in cat AI has been well documented, little is known about the internal organization of AAF beyond tonotopy. We studied how basic receptive field parameters (RFPs) are spatially organized in AAF with single- and multiunit recording techniques. A distorted tonotopicity with an underrepresentation in midfrequencies (1 and 5 kHz) and an overrepresentation in the high-frequency range was found. Spectral bandwidth (Q-values) and response threshold were significantly correlated with characteristic frequency (CF). To ...
Reciprocal Modulatory Influences between Tonotopic and Nontonotopic Cortical Fields in the Cat
Journal of Neuroscience, 2010
Functional and anatomical studies suggest that acoustic signals are processed hierarchically in auditory cortex. Although most regions of acoustically responsive cortex are not tonotopically organized, all previous electrophysiological investigations of interfield interactions have only examined tonotopically represented areas. The purpose of the present study was to investigate the functional interactions between tonotopically and nontonotopically organized fields in auditory cortex. We accomplished this goal by examining the bidirectional contributions between the cochleotopically organized primary auditory cortex (A1) and the noncochleotopically organized second auditory field (A2). Multiunit acute recording procedures in combination with reversible cooling deactivation techniques were used in eight mature cats. The synaptic activity of A1 or A2 was suppressed while the neuronal response to tonal stimuli of the noninactivated area (A1 or A2) was measured. Response strength, neuronal threshold, receptive field bandwidths, and latency measures were collected at each recorded site before, during, and after cooling deactivation epochs. Our analysis revealed comparable changes in A1 and A2 neuronal response properties. Specifically, significant decreases in neuronal response strength, increases in neuronal threshold, and shortening of response latency were found in both fields during periods of cooling deactivation. The weak anatomical connections between the two fields investigated make these findings unexpected. Furthermore, the observed neuronal changes suggest a model of corticocortical interaction among auditory fields in which neither differences in the magnitude of anatomical projections nor cortical representation of sensory stimuli are reliable determinants of modulatory functions.
Sound frequency representation in cat auditory cortex
Neuroimage, 2004
Using the intrinsic signal optical recording technique, we reconstructed the two-dimensional pattern of stimulus-evoked neuronal activities in the auditory cortex of anesthetized and paralyzed cats. The average magnitude of intrinsic signal in response to a pure tone stimulus increased steadily as the sound pressure level increased. A detailed analysis demonstrated that the evoked signals at early frames were scaled by the sound pressure level, which in turn indicated the presence of a minimum level of sound pressure beyond which stimulus-related intrinsic signal can be generated. Intrinsic signals evoked significantly by pure tone stimuli of different frequencies were localized and arranged in an orderly manner in the middle ectosylvian gyrus, which indicates that the primary auditory field (AI) is tonotopically organized. The arrangement of optimal frequencies obtained from optical recordings of the same auditory cortex, which were conducted on different days, was highly reproducible. Furthermore, other auditory fields surrounding AI in the recorded area were allocated based on the observed tonotopicity. We also conducted unit recordings on the cats used for optical recording with the same set of acoustic stimuli. The gross feature of the arrangement of optimal frequencies determined by unit recordings agreed with the tonotopic arrangement determined by the optical recording, although the precise agreement was not obtained. D 2004 Elsevier Inc. All rights reserved.
Thalamic projections to fields A, AI, P, and VP in the cat auditory cortex
The Journal of Comparative Neurology, 1987
Thalamocortical projections to four tonotopic fields (A, AI, P, and VP) of the cat auditory cortex were studied by using combined microelectrode mapping and retrograde axonal transport techniques. Horseradish peroxidase (HRP) or HRP combined with either tritiated bovine serum albumin or nuclear yellow was injected into identified best-frequency sites of one or two different fields in the same brain. Arrays of labeled neurons were related to thalamic nuclei defined on the basis of their cytoarchitecture and physiology. In some cases, patterns of labeling were directly compared with thalamic best-frequency maps obtained in the same brain. We compared only patterns of labeling resulting from injections into similar parts of the frequency representation in different fields to insure that observed differences in patterns of labeling did not simply reflect differences in the frequency representation at the injection sites.
Experimental Brain Research, 1990
The interconnections of the auditory cortex with the parahippocampal and cingulate cortices were studied in the cat. Injections of the anterograde and retrograde tracer WGA-HRP were performed, in different cats (n = 9), in electrophysiologically identified auditory cortical fields. Injections in the posterior zone of the auditory cortex (PAF or at the PAF/AI border) labeled neurons and axonal terminal fields in the cingulate gyrus, mainly in the ventral bank of the splenial sulcus (a region that can be considered as an extension of the cytoarchitectonic area Cg), and posteriorly in the retrosplenial area. Labeling was also present in area 35 of the perirhinal cortex, but it was sparser than in the cingulate gyrus. Following WGA-HRP injection in AII, no labeling was found in the cingulate gyrus, but a few neurons and terminals were labeled in area 35. In contrast, no or very sparse labeling was observed in the cingulate and perirhinal cortices after WGA-HRP injections in the anterior zone of the auditory cortex (AI or AAF). A WGA-HRP injection in the cingulate gyrus Abbreviations: AAF = anterior auditory cortical field; aes = anterior ectosylvian sulcus; AI = primary auditory cortical field; AII= secondary auditory cortical field; ALLS=anterior-lateral lateral suprasylvian visual area; BF = best frequency; C = cerebral cortex; CC = corpus callosum; CIN = cingulate cortex; CL = claustrum; DLS = dorsal lateral suprasylvian visual area; DP = dorsoposterior auditory area; E=entorhinal cortex; IC=inferior colliculus; LGN = lateral geniculate nucleus; LV = pars lateralis of the ventral division of the MGB; LVe = lateral ventricule; MGB = medial geniculate body; OT = optic tract; OV = pars ovoidea of the ventral division of the MGB; PAF=posterior auditory cortical field; pes=posterio r ectosylvian sulcus; PLLS=posterior-lateral lateral suprasylvian visual area; PS = posterior suprasylvian visual area; PU = putamen; RE = reticular complex of thalamus; rs = rhinal sulcus; SC = superior colliculus; SS = suprasylvian sulcus; T = temporal auditory cortical field; TMB = tetramethylbenzidine; VBX=vent~:obasal complex of thalamus, external nucleus; VL=pars ventrolateralis of the ventral division of the MGB; VLS=ventrolateral suprasylvian visual area; VPAF=ventroposterior auditory cortical field; WGA-HRP = wheat germ agglutinin labeled with horseradish peroxidase; wm= white matter. Offprint requests to: E.M. Rouiller labeled neurons in the posterior zone of the auditory cortex, between the posterior ectosylvian and the posterior suprasylvian sulci, but none was found more anteriorly in regions corresponding to AI, AAF and AII. The present data indicate the existence of preferential interconnections between the posterior auditory cortex and the limbic system (cingulate and parahippocampal cortices). This specialization of posterior auditory cortical areas can be related to previous observations indicating that the anterior and posterior regions of the auditory cortex differ from each other by their response properties to sounds and their pattern of connectivity with the auditory thalamus and the claustrum.
Connections of the dorsal zone of cat auditory cortex
The Journal of Comparative Neurology, 1998
The present study examined the anatomic connections of the dorsal zone of cat auditory cortex (DZ). The DZ was discriminated physiologically from the primary auditory field (AI) on the basis of neuronal responses with long latency and broad or multipeaked tuning curves. Wheat germ agglutinin-horseradish peroxidase was then injected either by pressure or iontophoretically. The thalamocortical and corticothalamic connections of the DZ were visualized by the presence of retrogradely labeled neurons and anterogradely labeled terminal fields in the thalamus; ipsilateral corticocortical projections from other cortical fields were visualized by the presence of retrogradely labeled cells. Injections of tracer into the DZ retrogradely labeled cells mainly in the lateral division of posterior complex (Po) and in the dorsal division (MGd) of the medial geniculate body (MGB); fewer labeled cells were found in the ventral (MGv) and medial (MGm) divisions of the MGB and in the suprageniculate nucleus. The DZ projection to Po, MGv, and MGd was heavy and was more diffuse than the reciprocal thalamocortical projection; the projection to MGm was light. The corticothalamic terminations and thalamocortical cells projecting to the same part of the DZ were not superimposed rigidly. The DZ received cortical projections from AI and from the second, anterior, and posterior auditory fields, and there were strong intra-DZ connections. Together with the physiological findings, the present results suggest that the DZ is a potentially separate auditory field from AI and is likely to be involved in both temporal and spectral integration of acoustic information.
Hearing Research, 1994
The sound pressure levei (SPL), henceforth termed intensity, of acoustic signals is encoded in the central auditory system by neurons with different forms of intensity sensitivity. However, knowledge about the topographic organization of neurons with these different properties and hence about the spatial representation of intensity, especially at higher levels of the auditory pathway, is limited. Here we show that in the tonotopically organized primary auditory cortex (Ai) of the cat there are orderly topographic organizations, along the isofrequency axis, of several neuronal properties related to the coding of the intensity of tones, viz. minimum threshold, dynamic range, best SPL, and non-monotonicity of spike count -intensity functions to tones of characteristic frequency CCF). minimum threshold, dynamic range, and best SPL are correlated and alter periodicaliy along isofrequency strips. The steepness of the high-intensity descending slope of spike count -intensity functions also varies systematically, with steepest slopes occurring in the regions along an isofrequency strip where low thresholds, narrow dynamic ranges and low best SPLs are found. As a consequence, CF-tones of various intensities are represented by orderly and, for most intensities, periodic, spatial patterns of distributed neuronal activity along an isofrequency strip, For low -to -moderate intensities, the mean relative activity along the entire isofrequency strip increases rapidly with intensity, with the spatial pattern of activity remaining quite constant along the strip. At higher intensities, however, the mean relative activity along the strip remains fairly constant with changes in intensity, but the spatial patterns change markedly. As a consequence of these effects, low-and high-intensity tones are represented by complementary distributions of activity alternating along an isofrequency strip. We conclude that in AI tone intensity is represented by two complementary modes, viz. discharge rate and place. Furthermore, the magnitude of the overall changes in the representation of tone intensity in AI appears to be closely related to psychophysical measures of loudness and of intensity discrimination.
The Journal of Comparative Neurology, 1990
The extent of a region containing acoustically responsive neurons within the anterior ectosylvian sulcus and its relationship to surrounding gyral auditory cortical fields was examined in chloralose-anaesthetized cats. Multiple microelectrode penetrations were made orthogonal to the middle and anterior ectosylvian gyral surfaces, and longer penetrations were made into the dorsal and ventral banks and fundus of the anterior ectosylvian sulcus. The quantitative and qualitative auditory response characteristics of neurons and neuron clusters in the sulcal banks and surrounding regions were mapped in detail, and the degree of overlap of auditory and visual neurons within the sulcus was determined by routinely testing for responsiveness to a gross light flash.