Functional organization of auditory projections to somatosensory cortical areas in cats

The functional properties of fibers transmitting auditory impulses to somatosensory areas S_I and S_II were studied in anesthetized and waking animals by the evoked potentials method. The thresholds of evoked potentials in areas S_I and S_II are 15–35 dB higher than those of evoked potentials in the auditory projection areas. Tonotopical localization is absent in somatic areas. Experiments on anesthetized animals showed that the spread of impulses relating to acoustic stimuli of different frequencies into areas S_I and S_II is effected through area A_I and its connections with the above zones. Another pathway probably also participates in the conduction of impulses from clicks. Analysis of the time constants of the first positive potential suggested that the interneuronal organization of auditory projections to area A_I is less complex than that of projections to the somatosensory areas. Comparison of amplitudes of evoked potentials of different projection zones in area S_I showed that the projection of the head receives more auditory impulses than the projection zone of the forelimbs, confirming the morphological data published previously.