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Front Syst Neurosci. 2013 Aug 30;7:43. doi: 10.3389/fnsys.2013.00043. eCollection 2013.

Saccades during visual exploration align hippocampal 3-8 Hz rhythms in human and non-human primates.

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1
Department of Psychology, Centre for Vision Research, York University Toronto, ON, Canada ; Department of Biology, Centre for Vision Research, York University Toronto, ON, Canada ; Neuroscience Graduate Diploma Program, York University Toronto, ON, Canada.

Abstract

Visual exploration in primates depends on saccadic eye movements (SEMs) that cause alternations of neural suppression and enhancement. This modulation extends beyond retinotopic areas, and is thought to facilitate perception; yet saccades may also influence brain regions critical for forming memories of these exploratory episodes. The hippocampus, for example, shows oscillatory activity that is generally associated with encoding of information. Whether or how hippocampal oscillations are influenced by eye movements is unknown. We recorded the neural activity in the human and macaque hippocampus during visual scene search. Across species, SEMs were associated with a time-limited alignment of a low-frequency (3-8 Hz) rhythm. The phase alignment depended on the task and not only on eye movements per se, and the frequency band was not a direct consequence of saccade rate. Hippocampal theta-frequency oscillations are produced by other mammals during repetitive exploratory behaviors, including whisking, sniffing, echolocation, and locomotion. The present results may reflect a similar yet distinct primate homologue supporting active perception during exploration.

KEYWORDS:

electrocorticography; epilepsy; foraging; human; macaque; phase-locking; saccades; theta

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