Figure 5.

Plasticity underlying SLRs is downstream of the mossy fibers. Top, Microstimulation of mossy fibers supported the acquisition of normal conditioned responses. The inset shows parasagittal sections from one animal, with the approximate locations of the tips of the stimulating electrode (MF) and internal cannula (AIN). Bottom, Sample traces from a subject during test sessions in which either muscimol (cyan) or gabazine (red) were infused into the AIN during paired sessions (left and center) or on the fifth session of extinction (right). Muscimol abolishes CRs (left), whereas gabazine unmasks SLRs (center) even after extinction (right).