# Electrophysiologic characterization of circadian rhythms of prefrontal cortical network states in a diurnal rodent

> **NIH NIH R21** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2024 · $195,192

## Abstract

ABSTRACT
There are clear circadian rhythms in the behavioral patterns of mammals and circadian disruption is one of the
most common co-morbidities in neuropsychiatric disorders. Behaviors themselves are instantiated via
electrophysiologic activity, such as neuronal action potentials or “spiking” and oscillations. However, we do not
know how circadian behavioral rhythms are brought about by electrophysiologic changes. To study the
circadian modulation of brain electrophysiology, rodent-based neuroscientific methods offer a powerful
platform, since they include tools to probe and record the electrical activity of neural circuits chronically, and in
great detail. Unfortunately, while humans are diurnal, the animal models used in neuroscience tend to be
nocturnal and therefore do not allow us to easily translate findings to humans. This is because nocturnal
animals do not simply represent phase-reversed versions of diurnal animals – there are non-linear differences
between nocturnal and diurnal animals in how brainwide neural circuits couple to the circadian pacemaker.
Therefore, to understand how neural circuits are modulated over the 24-hour cycle in a diurnal brain, we
propose to perform circadian timescale electrophysiologic recordings in a diurnal rodent. We will record from
the medial prefrontal cortex (mPFC), a region with both known import in rodent behavior and relation to human
psychiatric conditions including seasonal affective disorder (SAD) which is heavily affected by alterations in
circadian light patterns. For these long-timescale questions we will use non-traditional electrophysiologic
analytics amenable to chronic and non-stimulus locked quantification – an approach we call “Electrophysiologic
Background State” (EBS). This EBS approach will include a number of metrics of detailed spiking dynamics in
the mPFC amenable to analysis over sustained periods. These include excitatory-inhibitory balance and spike
rate variance which we have been suggested to be circadian modulated either in literature or our preliminary
data. Our hypothesis is that in diurnal species, EBS metrics in medial prefrontal cortex including population
spike rate variability and EI balance show daily rhythms that predict behavioral patterns. To test this hypothesis,
we propose to develop the first-ever chronic high-density electrophysiology in diurnal rodents using our
combination of expertise with diurnal Nile grass rat neurobiology (Yan) and rodent electrophysiology (Watson).
We propose to implant a 64-channel probe into the mPFC and then record for 96-hour periods in diurnal grass
rats. We will measure the spike rate variance and excitatory-inhibitory ratio to determine circadian modulation
of these measures. In the first aim we will determine light versus circadian modulation of any observed EBS
rhythms. In the second aim we will use reduced daylight to induce behavioral changes as in SAD patients and
will then correlate behavioral changes with EBS changes with...

## Key facts

- **NIH application ID:** 10757702
- **Project number:** 5R21MH131527-02
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Brendon O Watson
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $195,192
- **Award type:** 5
- **Project period:** 2023-01-01 → 2025-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10757702

## Citation

> US National Institutes of Health, RePORTER application 10757702, Electrophysiologic characterization of circadian rhythms of prefrontal cortical network states in a diurnal rodent (5R21MH131527-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10757702. Licensed CC0.

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