BURST-FIRING SHARPENS FREQUENCY-TUNING IN PRIMARY AUDITORY-CORTEX

FREQUENCY-TUNING in 46 high-firing single units from primary auditory cortex of ketamine-anaesthetized cats was studied separately for isola ted-spike firing and burst spike firing. The tuning curve for burst fi ring was significantly narrower than for the overall firing rate condi tion and, consequently, much narrower than for the isolated spikes. Th e burst firing was found in excess of that predicted from a modulated Poisson process, so the results cannot be explained on basis of a chan ge in firing rate criterion. We propose that burst firing in auditory cortex may selectively enhance frequency tuning dynamically controlled by the behavioural state of the animal as well as its stimulus histor y. Thus burst firing may have functional implications for cortical pro cessing.