Control of reaction time performance involves the striatum

Cats were tested for the effect of unilateral cooling of the centre median nucleus of the thalamus (CM) or of the caudate nucleus (Cd) as they performed a simple reaction time schedule. Shortening of reaction time occurred during CM cooling. Lengthening of the reaction time was observed during Cd cooling. Moreover, the Cd cooling was followed after a variable delay of a few minutes by a slowing down of the trial rate, and even by the arrest of performance for the lowest cooling temperature. The subject restarted at will after an arrest period, without motivational or motor disturbances, except for a short period of rotatory behaviour. The arrest period duration was about equal to the arrest period latency. Human subjects suffering from Parkinson's disease were tested with the same reaction time schedule. They showed lengthened reaction times and difficulty to perform reliably more than a ten of trials.