A1 Journal article (refereed)
Hippocampal electrical stimulation disrupts associative learning when targeted at dentate spikes (2017)

Nokia, M., Gureviciene, I., Waselius, T., Tanila, H., & Penttonen, M. (2017). Hippocampal electrical stimulation disrupts associative learning when targeted at dentate spikes. Journal of Physiology, 595(14), 4961-4971. https://doi.org/10.1113/JP274023

JYU authors or editors

Nokia, Miriam
Gureviciene, Irina
Waselius, Tomi
Penttonen, Markku

Publication details

All authors or editors: Nokia, Miriam; Gureviciene, Irina; Waselius, Tomi; Tanila, Heikki; Penttonen, Markku

Journal or series: Journal of Physiology

ISSN: 0022-3751

eISSN: 1469-7793

Publication year: 2017

Volume: 595

Issue number: 14

Pages range: 4961-4971

Publisher: Blackwell

Publication country: United Kingdom

Publication language: English

DOI: https://doi.org/10.1113/JP274023

Publication open access: Not open

Publication channel open access:

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/54982

Abstract

Hippocampal electrophysiological oscillations, namely theta and ripples, have been implicated in encoding and consolidation of new memories, respectively. According to existing literature, hippocampal dentate spikes are prominent, short‐duration (<30 ms), large‐amplitude (∼2–4 mV) fluctuations in hilar local‐field potentials that take place during awake immobility and sleep. Interestingly, previous studies indicate that during dentate spikes dentate gyrus granule cells increase their firing while firing of CA1 pyramidal cells are suppressed, thus resulting in momentary uncoupling of the two hippocampal subregions. To date, the behavioural significance of dentate spikes is unknown. Here, to study the possible role of dentate spikes in learning, we trained adult male Sprague–Dawley rats in trace eyeblink classical conditioning. For 1 h immediately following each conditioning session, one group of animals received hippocampal stimulation via the ventral hippocampal commissure (vHC) contingent on dentate spikes to disrupt the uncoupling between the dentate gyrus and the CA1 subregions. A yoked control group was stimulated during immobility, irrespective of brain state, and another control group was not stimulated at all. As a result, learning was impaired only in the group where vHC stimulation was administered contingent on dentate spikes. Our results suggest dentate spikes and/or the associated uncoupling of the dentate gyrus and the CA1 play a significant role in memory consolidation. Dentate spikes could possibly reflect reactivation and refinement of a memory trace within the dentate gyrus triggered by input from the entorhinal cortex.

Keywords: hippocampus

Free keywords: hippocampal electrical stimulation; associative learning; dentate spikes

Fields of science: