Frequency correlates on the auditory cortex of the cat brain

Response contours were constructed from measurements of evoked potentials for pure-tone stimuli, 15 to 35 db above threshold, using cats. The following criteria were used: response amplitude, initial latency, and peak latency. Wave shape was also examined. Widespread cortical response was obtained from pure tones. The point of maximal response was found either in AI or in AII for different cats. There were several cases of areas of large response which clearly extended through AI into AII. An examination of the response contours between cats as a function of frequency disclosed that the overlap was greater than the difference between the areas of maximum response. In addition, the distribution of points of largest response was not an orderly function of frequency. An examination of wave shape and response latency failed to provide a more orderly arrangement of frequency loci. Neither correlation between response amplitude and initial time nor the correlation between response amplitude and peak time was particularly large. The question is raised as to which measurement provides the “best fit” for the organization of the auditory cortex.