Neural correlates of auditory temporal-interval discrimination in cats.

Auditory temporal cues are very important in the perception of speech; nevertheless, the neural correlates underlying even a simple temporal task, such as interval discrimination, remain unclear, mainly due to the lack of comparable data of psychophysical and electrophysiological experiments in the same species. To address this, we measured both behavioral and neural responses in cats. Cats' ability to discriminate differences in sound intervals was tested by presenting two identical pure tone markers interrupted by intervals ranging from 10 to 320ms duration. All three subjects could accurately discriminate tones of 80-320ms interval from those of 10ms interval (correct rate>75%), but could not discriminate 20-40ms interval from 10ms interval. Neural responses to the same stimuli were recorded in the primary auditory cortex (A1) of three others awake cats. Consistent with previous studies, we found that the majority of A1 neurons showed a suppressed response to the second tone, and the amount of suppression generally increased with the decrease of intertone interval. Neurometric analysis revealed that neural responses could be used to discriminate the intertone interval, while discrimination performance was dependent on temporal precision to read the neural information. When spike activities were analyzed by 100ms bin size, 80% of neurometric functions matched the cats' psychometric function, suggesting a possible correlation between A1 activities and interval perception.