The lateral nucleus of the amygdala (LA) is the first site in the amygdala where the plasticity underlying fear conditioning could occur. We simultaneously recorded from multiple LA neurons in freely moving rats during fear conditioning trials in which tones were paired with foot shocks. Conditioning significantly increased the magnitude of tone-elicited responses (often within the first several trials), converted unresponsive cells into tone-responsive ones, and altered functional couplings between LA neurons. The effects of conditioning were greatest on the shortest latency (less than 15 ms) components of the tone-elicited responses, consistent with the hypothesis that direct projections from the auditory thalamus to LA are an important link in the circuitry through which rapid behavioral responses are controlled in the presence of conditioned fear stimuli.