Kindling limits the interictal neuronal temporal response properties in cat primary auditory cortex

PURPOSE: The present study examined the effect of electrical kindling on the interictal temporal response properties of single units recorded from primary auditory cortex (AI) of the adult cat. METHODS: Cats were permanently implanted with electrodes in AI, kindled twice daily for 40 sessions, and the contralateral AI was subsequently mapped. Kindling stimulation consisted of 1-s trains of biphasic square-wave pulses applied at a frequency of 60 Hz, 100 microA above the afterdischarge (AD) threshold. The EEG activity was recorded during each kindling session, and the behavioral manifestation was scored. Subsequent to kindling, multiple single-unit responses were recorded under ketamine anesthesia in response to 1-s-long periodic click trains, with click rates between 2 and 64 Hz. Neuronal responses were characterized according to their ability to respond in time-locked fashion to the clicks. RESULTS: Kindling stimulation resulted in progression of the AD characteristics and seizure behavior, with six of 10 kindled cats reaching a fully generalized state. In the fully kindled cats, the best modulation frequencies and limiting following rates for the single-unit responses were significantly lower compared with those of naive and sham controls. CONCLUSIONS: Repeated epileptiform activity interferes with temporal processing in cat auditory cortex in the interictal state. This may have implications for people with epileptic foci in auditory-related areas.