[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.

[Interaction of the somatosensory and auditory systems in awake cats at the level of the cortical projection zones]. / Vzaimodeistvie somatosensornykh i slukhovykh sistem u bodrstvuiushchikh koshek na urovne korkovykh proektsionnykh zon.

A comparative study of somato-acoustic interactions has been brought out by EP method in the auditory area A1 several projection areas of S1 and in S2 of non-immobilized cats with chronically implanted electrodes. Single cutaneous stimulation of the contralateral fore-leg with an intensity equal to 1.5 to 3 thresholds of EP appearance elicits in S1 and A1 three types of EPs differing in latencies and number of components. Preliminary rhythmic somatic stimulation has a predominantly facilitating effect on EPs appearing in response to tonal stimuli in the areas A1, S2, S1. Optimal conditions for facilitatory influences involve intervals of 250 to 500 msec, frequencies of somatic stimulation of 3 to 10 c/s and its intensity which does not elicit animal's motor reaction.

[Intercortical connections between the auditory fields and the motor area]. / Interkortikal'nye sviazi slukhovykh polei s motornoi oblast'iu.

The connections of auditory fields AI, AII and Ep with the motor area were studied in 14 cats by anterograde degeneration method by means of impregnation techniques of Nauta-Gigax and Fink-Heimer in Victorov's modification. Direct connections were established between the three auditory fields and the motor projection field of the forepaw. The connections coming from the auditory field Ep spread wider, to the motor projection field of the head. The greatest number of these interzonal connections originates in zone Ep, and the smallest in AII zone.

[Functional organization of pathways transmitting auditory signals in the somatosensory zone of the cat cerebral cortex]. / Nekotorye osobennosti funktsional'noi organizatsii putei peredachi slukhovykh signalov v zony somaticheskoi chuvstvitel'nosti kory bol'shikh polusharii koshki

The functional properties of the auditory projections to the somatosensory zones S2 and S were studied by recording evoked potentials in anesthetized and vigil unrestrained cats. The thresholds of evoked potentials recorded from SI and SII were higher by 15--35 db than those from AI. No tonotopical localization was found in SI and SII. Signals about pure tones of different frequencies were conducted to SI and SII via area AI. The signals about clicks were ascending to SI and SII not only through this pathway, but also through other ones. It suggested from the time constants analysis of the first positive wave of the evoked potentials that the interneuronal organization of the cortical auditory projections to AI is not so comples as that to SI and SII. The differences in amplitudes of evoked potential recorded in SI indicate that the head projection areas receive higher portion of the auditory projections. This is confirmed by the morphological evidence.