Synchronized Oscillatory Activities of the Human Amygdala and Hippocampus during Emotional Learning in Epileptic Patients

The interactions of the amygdala with other brain regions during emotional learning have been studied by single cell and local field potential (LFP) recordings in animals. Recently, a synchronization of theta activity in the amygdalohippocampal network has been described as a correlate of conditioned fear. We investigated synchronized oscillatory activities during emotional learning in humans. Deep electrode ERP recordings (LFPs) were obtained from electrode arrays implanted in the human temporal lobe during invasive presurgical monitoring of N=26 epileptic patients. Contact sites were located within the amygdala, hippocampus, as well as several neocortical sites. We report here on cross correlation data from left (N=12) and right amygdala and anterior hippocampus (N=13) contacts to evaluate synchronized activities in the LFP signal during a differential conditioning procedure [a fear face was paired with an aversive acoustic UCS, (CS+) and a neutral face was used as a within-subject control condition (CS-)]. The results indicate that stable ERPs could be obtained, emerging reliably from contacts in right amygdala and anterior hippocampus. A differential response to CS+ and CS+-alone trials as compared to CS- was found in amygdala and anterior hippocampus LFPs at 450 ms. Event-related synchronizations (ERS) in the theta-band indicated neural coupling of the amygdala and hippocampus as well as temporolateral regions. The findings provide evidence for an involvement of amygdala-hippocampus interactions during emotional memory formation in humans. (DFG Pe 499/3–2).