[Cortico-cortical connections between the auditory fields and the sensomotor area of the cortex]. / Kortiko-kortikal'nye sviazi slukhovykh polei s sensomotornoi oblast'iu kory.

In 18 cats by means of two methods--anterograde degeneration and retrograde transport of exogenic horseradish peroxidase--cortico-cortical connections of the auditory fields to the cortical sensomotor area have been studied. These connections have been stated to terminate in layers V-III of certain parts of the sensomotor area corresponding to the projections of the foreleg and the head. Initial neurons of the connections studied are pyramidal cells in layers III and II. They are situated in rostral and caudal parts of the fields AI and AII, but within these levels they occur in different areas of the auditory fields.

[Horseradish peroxidase labelled neurons of nonspecific thalamic nuclei projecting to the cat brain somatosensory zone I]. / Mechennye peroksidazoi khrena neirony nespetsificheskikh iader talamusa, proetsiruiushchiesia v I somatosensornuiu zonu kory mozga koshki.

The morphology and topography of neurons whose axons form the thalamic nonspecific input to the primary somatosensory cortex were studied in the cat thalamus by the method of the retrograde transport of the horseradish peroxidase. The labelled cells were found in the dorsolateral part of the nucleus ventralis anterior, in the nucleus centralis lateralis, in the lateral part of the nucleus dorsalis medialis, in the dorsal part of the nucleus centrum medianum. A very small number of slightly stained cells were found in the nucleus paracentralis. The variety of the shape, size and intensity of labelling of the HRP-positive cells was observed in each thalamic structure. The results of the experiments indicate that not only the ventrobasal complex but also the nonspecific thalamic nuclei are projected to the primary somatosensory cortex. These data demonstrate the existence of multiple afferent thalamic inputs to the primary somatosensory cortex.

[Horseradish peroxidase labeled neurons of the ventrobasal complex of the thalamus projecting to the somatosensory zone I of the cat cerebral cortex]. / Mechennye peroksidazoi khrena neirony ventrobazal'nogo kompleksa talamusa, proetsiruiushchiesia v I somato-sensornuiu zonu kory mozga koshki.

The morphology and topography of the neurons in the ventro-basal complex (VB) projecting to the somatic sensory cortex (SI) were studied by the method of the retrograde axonic transport of horseradish peroxidase (HRP). Different types of HRP-labelled cells were found in this structure. The concentration of labelled cells was the greatest in the central part of the VB. The most peculiar feature in the distribution of HRP-positive neurons was their organization in two large populations in the dorsal and ventral portions of the VB. A comparison with the somatotopic map of the VB revealed that the central region of this complex is the area of the representation of the forelimb and the head. Our morphological results confirm the neurophysiological conception about the organization of the thalamo-cortical input on the "point-to-point" projection principles.