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Optogenetic Entrainment of Hippocampal Theta Oscillations in Behaving Mice
Published on: June 29, 2018
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Precisely timed theta oscillations are selectively required during the encoding phase of memory.
Clare R Quirk1, Ipshita Zutshi1, Sunandha Srikanth1
1Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA, USA.
Nature Neuroscience
|October 5, 2021
Summary
Altering brain rhythms in the medial septal area disrupts memory encoding. Specifically, pacing neuronal firing above the natural theta frequency impaired spatial working memory in mice.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Computational Neuroscience
Background:
- Brain oscillations, particularly theta rhythms (6-9 Hz) in the entorhinal cortex and hippocampus, are crucial for learning and memory.
- These theta oscillations are regulated by pacemaker cells in the medial septal area.
- The precise role of precise neuronal timing in cognitive functions remains debated.
Purpose of the Study:
- To investigate whether precise neuronal timing, driven by medial septal area oscillations, is critical for cognitive functions like spatial working memory.
- To determine if perturbing neuronal firing patterns at specific frequencies impacts memory encoding.
Main Methods:
- Utilized optogenetic stimulation to rhythmically activate parvalbumin-positive neurons in the medial septal area of mice.
- Applied rhythmic optical stimulation at various frequencies, including those at and above the endogenous theta frequency.
- Assessed spatial working memory performance using a spatial working memory task.
- Correlated neuronal activity patterns with memory performance during task performance.
Main Results:
- Rhythmic optical stimulation of medial septal area neurons successfully entrained entorhinal and hippocampal neuronal activity patterns.
- Spatial working memory was not impaired when pacing frequencies were at or below the endogenous theta frequency.
- Memory impairments emerged specifically at pacing frequencies of 10 Hz and above.
- These impairments were most pronounced when pacing targeted neural activity during the encoding phase of the task.
Conclusions:
- Precise neuronal timing, particularly during the encoding phase, is critical for spatial working memory.
- Perturbing neuronal firing patterns by pacing above the endogenous theta frequency selectively disrupts neural computations essential for memory encoding.
- These findings highlight the functional significance of neural timing in cognitive processes.
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