Coherent gamma oscillations couple the amygdala and striatum during learning

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Abstract
It has been suggested that the basolateral amygdala mediates emotional enhancement of memory. Here, the authors suggest a potential mechanism for this process, showing that coherent gamma oscillations coordinate amgydalostriatal interactions during learning. This coupling could facilitate synaptic plasticity. The basolateral amygdala (BLA) mediates the facilitating effects of emotions on memory. The BLA's enhancing influence extends to various types of memories, including striatal-dependent habit formation. To shed light on the underlying mechanisms, we carried out unit and local field potential (LFP) recordings in BLA, striatum, auditory cortex and intralaminar thalamus in cats trained on a stimulus-response task in which the presentation of one of two tones predicted reward delivery. The coherence of BLA, but not of cortical or thalamic, LFPs was highest with striatal gamma activity, and intra-BLA muscimol infusions selectively reduced striatal gamma power. Moreover, coupling of BLA-striatal unit activity increased when LFP gamma power was augmented. Early in training, the rewarded and unrewarded tones elicited a modest increase in coherent BLA-striatal gamma. As learning progressed, this gamma coupling selectively increased in relation to the rewarded tone. Thus, coherent gamma oscillations coordinate amygdalostriatal interactions during learning and might facilitate synaptic plasticity.