# Local infrared stimulation modulates spontaneous cortical slow wave dynamics in anesthetized rats

## TL;DR

Local infrared stimulation can change brain wave patterns in anesthetized rats, offering a new way to study brain activity.

## Contribution

This study introduces a minimally invasive method using infrared light to modulate cortical slow waves in specific brain regions.

## Key findings

- NIR stimulation shortened up-state durations and prolonged down-states in cortical slow waves.
- Multi-unit activity amplitudes increased during up-states with steeper transition slopes.
- PtA showed increased slow wave and high delta activity, while S1Tr showed a reduction trend.

## Abstract

Cortical slow waves are hallmark oscillations of deep sleep and certain anesthetic conditions, yet the neurobiological mechanisms controlling their dynamics remain incompletely understood. Here, we investigated the effects of local near-infrared (NIR) stimulation on slow-wave activity in ketamine/xylazine-anesthetized rats. Using a silicon-based multimodal optrode, we simultaneously delivered NIR light and recorded local field potentials (LFPs) and multi-unit activity (MUA) across cortical layers in the primary somatosensory (S1Tr) and parietal association (PtA) cortices. NIR stimulation induces local tissue heating, resulting in reproducible and reversible changes in the properties of slow waves. Specifically, up-state durations were shortened, down-states prolonged, and MUA amplitudes during up-states increased, with steeper slopes at state transitions, indicative of enhanced neuronal synchronization. LFP amplitude and spectral changes varied across cortical regions: PtA exhibited increased slow wave (0.5–2 Hz) and high delta (2–4 Hz) band activity, while S1Tr showed a trend toward reduction. Our findings demonstrate that local infrared stimulation can reliably modulate cortical slow-wave dynamics, likely through temperature-mediated changes in neuronal excitability. This approach provides a minimally invasive method for precise, local manipulation of cortical network activity and offers new insights into the biophysical regulation of slow oscillations.

The online version contains supplementary material available at 10.1038/s41598-026-38781-4.