Functional organization and integrative mechanism on the auditory cortex of the cat

Abstract

1. Single unit analyses have been done in 180 cortical auditory neurons of cats anesthetized with barbiturate. 2. A new type of the response area was found besides the flat type and the sharp peak type. The neurons of this type had multi-peaks in their response area. 3. An example of the multi-peak type was shown, and its response area and pattern suggested the direct projection of afferent fibers from the neurons of the medial geniculate body. 4. The flat type had the longest mean latency, followed the multi-peak type, and the sharp peak type. 5. The type of the response area changed from the flat type to the multipeak tpe or sharp peak type after the depth of the neurons encountered in a penetration. 6. The neurons obtained from a vertical penetration had the same characteristic frequency, and were presumed to be in a functional vertical column which was determined by the best frequency. 7. Many types of the response areas were involved in the neurons of the same penetration, and an integrative mechanism of the frequency was consid ered to be the convergence from the sharp peak type to the flat type via multi-peak type. 8. The changes in response properties caused by the two-tone stimulation were studied. The effect was more conspicuous in facilitation rather than inhibition, and observed mainly in the neurons with the narrow response area. 9. Facilitation occurred even when the two stimulating sounds did not give a beat, and the effective frequency range of some neurons was three bands far apart from their characteristic frequencies. 10. The effect differed after the frequency and intensity relation of the two tones. 11. In some cortical cells, the on response underwent different changes from that of the off response. 12. The threshold values were lowered especially at the high threshold frequency range of the response areas, and a new peak appeared in the response areas. 13. This facilitatory effect caused by the two-tone stimulation suggests that the cortical cells were sensitive to the change in frequency and intensity of the tonal stimuli, which seemed to be related to the discrimination of the complex sound. © 1965, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.