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J Neurosci. 2015 Sep 30;35(39):13323-35. doi: 10.1523/JNEUROSCI.2278-15.2015.

Bidirectional Modulation of Recognition Memory.

Author information

1
Department of Cognitive, Linguistic and Psychological Sciences and.
2
Department of Neuroscience, Brown University, Providence, Rhode Island 02912.
3
Department of Cognitive, Linguistic and Psychological Sciences and Department of Neuroscience, Brown University, Providence, Rhode Island 02912 rebecca_burwell@brown.edu.

Abstract

Perirhinal cortex (PER) has a well established role in the familiarity-based recognition of individual items and objects. For example, animals and humans with perirhinal damage are unable to distinguish familiar from novel objects in recognition memory tasks. In the normal brain, perirhinal neurons respond to novelty and familiarity by increasing or decreasing firing rates. Recent work also implicates oscillatory activity in the low-beta and low-gamma frequency bands in sensory detection, perception, and recognition. Using optogenetic methods in a spontaneous object exploration (SOR) task, we altered recognition memory performance in rats. In the SOR task, normal rats preferentially explore novel images over familiar ones. We modulated exploratory behavior in this task by optically stimulating channelrhodopsin-expressing perirhinal neurons at various frequencies while rats looked at novel or familiar 2D images. Stimulation at 30-40 Hz during looking caused rats to treat a familiar image as if it were novel by increasing time looking at the image. Stimulation at 30-40 Hz was not effective in increasing exploration of novel images. Stimulation at 10-15 Hz caused animals to treat a novel image as familiar by decreasing time looking at the image, but did not affect looking times for images that were already familiar. We conclude that optical stimulation of PER at different frequencies can alter visual recognition memory bidirectionally. Significance statement: Recognition of novelty and familiarity are important for learning, memory, and decision making. Perirhinal cortex (PER) has a well established role in the familiarity-based recognition of individual items and objects, but how novelty and familiarity are encoded and transmitted in the brain is not known. Perirhinal neurons respond to novelty and familiarity by changing firing rates, but recent work suggests that brain oscillations may also be important for recognition. In this study, we showed that stimulation of the PER could increase or decrease exploration of novel and familiar images depending on the frequency of stimulation. Our findings suggest that optical stimulation of PER at specific frequencies can predictably alter recognition memory.

KEYWORDS:

brain oscillations; familiarity; novelty; optogenetics; perirhinal; vision

PMID:
26424881
PMCID:
PMC4588607
DOI:
10.1523/JNEUROSCI.2278-15.2015
[Indexed for MEDLINE]
Free PMC Article

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