Area 39 and 41 neurons sensitive to acoustic stimulation in the rat cortex: Polysensory properties

Abstract

A comparative analysis of the polysensory properties of 102 neurons in areas 39 and 41 (the associative and auditory cortices, respectively) was performed in acute experiments on rats under chloralose-nembutal anesthesia. In the auditory cortex, the evoked potentials (EP) recorded from the surface of the above area in response to acoustic tonal, electrical cutaneous, and light stimulations almost always were distinguished by their shorter (4–5 msec) latency and higher amplitude. We studied neurons in both areas; their responses to the pure tones of various frequencies and to the stimulations of other modalities were compared. Bi- and polysensory neurons constituted 56.4% in area 39, and only 23% in area 41. The depth distribution of the responding neurons in areas 39 and 41 was different. Neurons with selective sensitivity to different frequencies of tonal signals were found in both areas. Usually monomodal neurons demonstrated selective properties in the auditory cortex, and 70% of them had a characteristic frequency. Over one-half of polymodal cells were frequency-selective in the associative cortex.