Krista Wahlstrom, University of Iowa
ABSTRACT: Although evidence suggests that the basolateral amygdala (BLA) and dorsal hippocampus (DH) work together to influence the consolidation of spatial/contextual learning, the circuit mechanism by which the BLA selectively modulates spatial/contextual memory consolidation is not clear. The medial entorhinal cortex (mEC) is a critical region in the hippocampus-based system for processing spatial information. As an efferent target of the BLA, the mEC is a candidate by which the BLA influences the consolidation of such learning. To address several questions regarding this issue, male Sprague-Dawley rats received optogenetic manipulations of different BLA afferents immediately after training in different learning tasks. Optogenetic stimulation of the BLA-mEC pathway using ChR2(E123A) following spatial and cued-response Barnes maze training enhanced and impaired retention, respectively. Only stimulation using bursts of 8 Hz light pulses significantly altered retention in either task, suggesting the importance of driving activity in this frequency range. 8 Hz stimulation of the BLA-mEC pathway increased local field potential power in the same frequency range in the mEC and in the DH. Together, the present findings suggest that the BLA modulates the consolidation of spatial memory via projections to the mEC and that activity within the 8 Hz range is critical for this modulation.