# Frequency‐ and Layer‐Specific Modulation of Cortical Neuronal Activity by Pulsed Electrical Stimulation

## TL;DR

This study shows how different electrical stimulation frequencies affect brain neurons, revealing that high frequency boosts excitatory neuron activity while both frequencies impact inhibitory neurons.

## Contribution

The study identifies frequency- and layer-specific effects of pulsed electrical stimulation on cortical neurons using two-photon Ca2+ imaging in mice.

## Key findings

- High-frequency stimulation increases Ca2+ activity in layer 2/3 excitatory neurons during and after stimulation.
- Low-frequency stimulation enhances excitatory neuron activity only post-stimulation and transiently suppresses it during stimulation in layer 5.
- Both stimulation frequencies enhance inhibitory neuron activity in layer 2/3 during stimulation.

## Abstract

Electrical stimulation is a common technique in neuroscience and clinical therapies, with stimulation frequency being a critical factor in its efficacy. However, the cellular mechanisms by which different frequencies of pulsed electrical stimulation modulate neuronal activity remain poorly understood. In this study, we explore the effects of 60 Hz (low frequency [LF]) and 160 Hz (high frequency [HF]) pulsed electrical stimulation on excitatory and inhibitory neurons in the primary somatosensory cortex (S1) of mice using two‐photon Ca2+ imaging. Our results show that HF stimulation significantly increased Ca2+ activity in excitatory neurons in layer 2/3, both during and after stimulation, while LF stimulation enhanced neuronal activity only post‐stimulation. In layer 5 excitatory neurons, HF stimulation increased neuronal activity only after stimulation cessation, whereas LF stimulation transiently suppressed activity during stimulation. Both LF and HF stimulation enhanced activity in inhibitory neurons in layer 2/3 during stimulation. In summary, our study reveals that electrical stimulation activates both excitatory and inhibitory neurons, with its primary mechanism of action being the modulation of neuronal rhythm rather than the amplitude of their activity. These findings shed light on stimulation mechanisms, supporting its therapeutic potential for neuropsychiatric disorders targeting neuronal rhythmicity.

High‐frequency electrical stimulation induces stronger activation in excitatory neurons, while both frequencies enhanced similar activation in inhibitory neurons. Both frequencies modulate neuronal rhythm and coherence in excitatory and inhibitory neurons similarly. These findings elucidate frequency‐specific modulation of excitatory and inhibitory neurons, providing a mechanistic foundation for optimizing therapeutic brain stimulation protocols.