Figure 1.

A schematic showing how eyelid conditioning engages the cerebellum. The tone-CS activates mossy fiber inputs from the pontine nuclei, mild electrical stimulation around the eye (US) activates climbing fiber inputs (green), and output from the AIN of the cerebellum drives CR expression (blue trace). Removing or pharmacologically disconnecting the cerebellar cortex via GABA_A antagonists in the AIN or by electrolytic lesions of Purkinje cells (dotted blue) unmasks SLRs (red trace). The expression pathway underlying SLRs and the essential site of plasticity was localized using a variety of treatments, including glutamate receptor antagonists [experiment 1 (E1) and E2], the GABA_A agonist muscimol (E1–4), and microstimulation of mossy fibers (E3, 4).