DESCRIPTION (provided by applicant): Considerable evidence implicates the lateral nucleus of the amygdala (LA) as a key structure in the acquisition and retention of fear mediated behavior, including auditory fear conditioning in which a neutral conditioned stimulus (CS) such as a tone is paired with an aversive unconditioned stimulus (US) such as a shock. At the cellular level, this type of associative learning is thought to require co-activation of LA neurons by two sets of synaptic inputs; specifically, a weak CS and a strong US. During this synaptic activation, the two inputs are integrated to produce long-term plasticity in LA. In the laboratory, this type of associative plasticity is modeled in vitro using associative long-term potentiation (LTP). The aim of this proposal is to examine how two sets of synaptic inputs might be integrated within the dendritic arbors of a single LA neuron and to show how such integrations might produce long-term plasticity (LTP) in LA, in vitro. Aim I of the proposed studies will address how two sets of synaptic inputs summate in individual LA neurons. Aim II will address how the relative timing of the two inputs affects summation. Aim III will address how the integrative properties of LA neurons can affect the mechanism of LTP induction in LA. Two specific mechanisms, the back-propagating action potential and dendritic regenerative events, proposed to underlie LTP induction in hippocampus will be tested in LA.