3/9/2023 0 Comments Auditory cortex locatedFour different tonotopically- organized fields could be distinguished: two fields with a mirror-imaged tonotopy had adjacent high frequency representations, the low frequency representation were rostral in a smaller anterior field (AAF) and caudal in a large field (AI). Six fields were distinguished on the basis of frequency representation. The auditory cortex of the Mongolian gerbil has been studied extensively using electophysiological recording techniques ( Thomas et al., 1993), 2-deoxyglucose (2DG) autoradiographic labeling ( Scheich et al., 1993) and anterograde tracer biocytin ( Budinger et al., 2000). Previous electrophysiological mapping studies have provided evidence that the rodent auditory cortex, like that of other mammals, consists of multiple topographically-organized cochlea projections. Key terms: auditory cortex, cortical connections, laminar patterns, fluorescent tracer-retrograde labeling.Īnatomical and physiological studies have greatly expanded our knowledge of the organization of the mammalian auditory cortex. In both hemispheres, the supragranular layer III contains the greatest concentration of cortico-cortical cells bodies the granular and infragranular layer V contains a somewhat lower concentration. In general, regions near the injection sites receive more densely-labeled projections than do more distant targets. Substantial numbers of retrogradedly labeled neurons with similar best frequencies (BFs) were observed in the ipsilateral and moderate to scant numbers in the contralateral hemisphere. In all cases, patches of labeling are distributed along 2DG bands oriented parallel to the isofrequency line. In AI, DP and VP, neurons are connected with AAF in the ipsilateral hemisphere and AI and AAF in the opposite hemisphere. This area also receives projections from AI, AAF and D from the contralateral hemisphere. Neurons in AAF, DP, VP and V project to AI in the ipsilateral hemisphere. Injections of fluorescent tracer were placed in electrophysiologically-identified locations of AI and AAF. Distributions of axons were examined by means of retrogradely-transported fluorescent tracer Fast Blue (FB) injected in the primary (AI) and anterior (AAF) auditory field. Topographic distributions and laminar pattern of cortico-cortical projections from the primary auditory field (AI), anterior auditory field (AAF), dorsoposterior field (DP), ventroposterior field (VP), dorsal field (D) and ventral field (V) were studied in relation to tonotopic maps in combined anatomical, electrophysiological and 2-deoxyfluoro-D-glucose (2DG) experiments. Comparative study of inter-and intrahemisphericĬortico-cortical connections in gerbil auditory cortexġ Instituto de Fisiología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile.Ģ Escuela de Psicología, Pontificia Universidad Católica de Chile, Santiago, Chile.Ĭorresponding Author: Hardy Thomas, Instituto de Fisiología, Facultad de Medicina, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.
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