Synaptic strength dynamics.

(A) Evolution of synaptic strength during presentation of odor sequences (columns) as in Figure 5. Top row: SRDP; bottom row: STDP. In every diagram, the strength of each PN-KC synapse is color coded, from bottom to top, across the 200 1-s learning trials (vertical axis). The corresponding KC is indicated on the horizontal axis, 10 synapses per KC (dotted grid). Values normalized to the initial conductance g* and represented color coded as percentage of change. Note how STDP induces more selective and less dramatic changes. (B) Distribution of synaptic strengths during learning after 50, 100, 150, and 200 learning trials (columns), as in Figure 5. Top box: SRDP; bottom box: STDP. Each box compares values for single odor learning (upper row) with values for learning odor sequences (lower row). Single odor distributions include the average synaptic values for the four odors 1, 2, 3, and 4, whereas sequence distributions include the average synaptic values for the odor sequences “1234,” “2143,” “3421,” and “4321.” Normalization as in (A). Vertical red lines indicate mean values. (C) Average (±SEM) synaptic value during learning of single odors (blue) or odor sequences (red). Values and normalization as in (A).