Figure 10.

Theta burst firing decreases synaptic plasticity. Synaptic plasticity, measured here as LTP of a thalamic evoked EPSP, can be induced in the BLA. A, This LTP is observed in conditions when TBF is ineffective at changing membrane properties (top; TBF without being paired with depolarization). In conditions that promote TBF effects on membrane properties (TBF paired with depolarization), LTP is absent (bottom). B, When TBF is only moderately effective at inducing a change of membrane properties [30 s TBF paired with depolarization (depol)], LTP is attenuated but not absent. C, LTP induced after the weak TBF protocol is accompanied by a change of paired-pulse ratio, indicative of a presynaptic change during LTP. When LTP is blocked by previous TBF, a change of paired-pulse ratio is also blocked.