• Bénédicte Amilhon, Carey Y L Huh, Frédéric Manseau, Guillaume Ducharme, Heather Nichol, Antoine Adamantidis, and Sylvain Williams.
• Department of Psychiatry, Douglas Mental Health University Institute, McGill University, 6875 Lasalle Boulevard, Montréal, QC H4H 1R3, Canada. Electronic address: benedicte.amilhon@douglas.mcgill.ca.
• Neuron. 2015 Jun 3; 86 (5): 1277-89.

AbstractHippocampal theta rhythm arises from a combination of recently described intrinsic theta oscillators and inputs from multiple brain areas. Interneurons expressing the markers parvalbumin (PV) and somatostatin (SOM) are leading candidates to participate in intrinsic rhythm generation and principal cell (PC) coordination in distal CA1 and subiculum. We tested their involvement by optogenetically activating and silencing PV or SOM interneurons in an intact hippocampus preparation that preserves intrinsic connections and oscillates spontaneously at theta frequencies. Despite evidence suggesting that SOM interneurons are crucial for theta, optogenetic manipulation of these interneurons modestly influenced theta rhythm. However, SOM interneurons were able to strongly modulate temporoammonic inputs. In contrast, activation of PV interneurons powerfully controlled PC network and rhythm generation optimally at 8 Hz, while continuously silencing them disrupted theta. Our results thus demonstrate a pivotal role of PV but not SOM interneurons for PC synchronization and the emergence of intrinsic hippocampal theta.Copyright © 2015 Elsevier Inc. All rights reserved.

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