RESPONSE PROPERTIES OF UNITS IN THE POSTERIOR AUDITORY FIELD DEPRIVEDOF INPUT FROM THE IPSILATERAL PRIMARY AUDITORY-CORTEX

The influence of the ipsilateral primary auditory field (AI) on the re sponse properties of neurons in the posterior auditory field (Field P) was examined in three cats anesthetized with sodium pentobarbital. Ra te/level functions were obtained, by extracellular recording, from sin gle units in Field P before (n=38) and after (n=50) subpial aspiration of AI. The ablations were primarily confined to the medial ectosylvia n gyrus, although in one case extended into the high-frequency portion of the anterior auditory field. Comparisons between the behavior of u nits isolated before and after AI ablation failed to demonstrate any c hanges in the response properties of neurons in Field P attributable t o the ablation. Nonmonotonic response profiles, first spike latency, v ariability in latency, threshold and maximal discharge rates of the un its to acoustic stimuli were not significantly altered by the AI ablat ion. These results indicate that the basic response properties of neur ons in Field P do not depend on input from the ipsilateral AI. This su ggests that these properties are most likely determined by thalamic in put or by circuitry within Field P.