[Tonotopic organization of the dorsocaudal zone of auditory area AII of the cerebral cortex in the cat].

Tonotopic organization of dorsocaudal zone of secondary auditory area (AII) was studied in acute nembutal-anaesthetized cats. Neurons of this zone responded selectively to acoustic stimuli of definite frequencies. 74% of units had one best frequency. 26% of units had several best frequencies while 7% responded in all the range tested and had no best frequency. Neurons with low best frequencies were localized in upper part of sylvian gyrus near posterior ectosylvian sulcus. Successive increase of best frequencies occurred during ventrorostral shifting of the recorded point along the sylvian gyrus. The distance between low frequency and high frequency foci in the dorsocaudal projection zone was 2.5-3.5 mm. Neurons with close values of best frequency organized in vertical columns could differ substantially as to dimensions of receptive fields, precision of frequency selectivity and patterns of impulse responses.