Neuron
Volume 86, Issue 5, 3 June 2015, Pages 1277-1289
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Article
Parvalbumin Interneurons of Hippocampus Tune Population Activity at Theta Frequency

https://doi.org/10.1016/j.neuron.2015.05.027Get rights and content
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Highlights

  • PV interneuron optogenetic activation drives intrinsic HP theta optimally at 8 Hz

  • PV interneuron optogenetic silencing disrupts intrinsic theta oscillations

  • SOM interneurons are weakly involved in theta generation at the local network level

  • SOM interneurons modulate the entrainment of intrinsic theta rhythm by EC inputs

Summary

Hippocampal 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.

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