One group within CCL works with electrophysiological techniques in order to understand the of timing of movement at the level of individual nerve cells. In particular, we study timing in classical (Pavlovian) conditioning of a blink response. A subject receives a neutral stimulus (e.g. a tone) followed by a puff of air to the eye. The tone does not evoke any response but the air puff elicits a blink. After a number of paired presentations of tone and air puff, the tone will elicit a blink just before the air puff where the protective effect is maximal. This conditioned response is adaptively timed, which means that if the interval between tone and air puff is increased, the delay of the conditioned blink will, after additional training, be increased by a corresponding amount, so that the conditioned response will again occur just before the air puff.
We have identified cells in the cerebellum of ferrets that control the learned blink and we can record the activity of these cells with microelectrodes during learning and extinction. We can also use direct electrical stimulation of pathways into the cerebellum instead of tones and air puffs. We have found a new kind of learned cellular response in Purkinje cells in the cerebellum. These responses have many properties (such as adaptive timing) that mimic the overt behavioural responses (blinks). We believe that these Purkinje cell responses drive the behaviour. The experimental work is currently focused on identifying the mechanisms underlying the timing of the Purkinje cell responses.