FUNCTIONAL TOPOGRAPHY OF CAT PRIMARY AUDITORY-CORTEX - RESPONSE LATENCIES

Minimum onset latency (L-min) of single-and multiple-unit responses we re mapped in the primary auditory cortex (AI) of barbiturate-anestheti zed cats. Contralateral L-min for multiple units was non-homogeneously distributed along the dorso-ventral/isofrequency axis of the AI. Resp onses with shorter latencies were more often located in the central, m ore sharply tuned region while longer latencies were more frequently e ncountered in the dorsal and ventral portions of the AI. For single un its, a large scatter of L-min values was found throughout the extent o f the AI including cortical depth. The relationship between L-min and previously reported spectral, intensity and temporal parameters was an alyzed and revealed statistically significant correlations between min imum onset latency and the following response properties in some but n ot all studied animals: sharpness of tuning of a frequency response ar ea 10 dB above threshold, broadband transient response, strongest resp onse level, monotonicity of rate/level functions, dynamic range, and p referred frequency modulation sweep direction. This analysis suggests that L-min is determined by several independent factors and that the p rediction of L-min based on relationships with other spectral and temp oral response properties is inherently weak. The spatial distribution and the functional relationship between these response parameters may provide an important aspect of the time-based cortical representation of specific features in the animal's natural environment.