Figure 7.

Synaptic traces during behavioral protocol. A, OF exploration preceding inhibitory avoidance training (OF → IA) by 1 h. Top, Weight traces of three individual synapses (blue lines) from input neurons active in the training cage to neurons in the spatial population. Bottom, Mean weight over all synapses originating from input neurons that are highly active in the training cage. B, As in A but with a delay of 2 h between OF and training. C, OF exploration following inhibitory avoidance training after 30 s. Top, Individual synaptic weight traces. Bottom, Mean synaptic weight. Note the rapid increase and immediate reset of weights. D, As in C but with a time difference of 15 min. During OF exposure, synapses are depotentiated. Whereas one of the sample synaptic weight traces (blue) remains at the low value after the OF stimulation, two others recover to their high values. The result for the mean weight (black line, 113% at t = 15 minutes and 109% at t = 40 minutes) indicates that ∼70% of those synapses that were tagged before OF exposure returned to their high efficacy values thereafter.