# Enhancing visual perception by modulating prestimulus alpha and beta power with tRNS

## TL;DR

This study shows that using tRNS to modulate brain waves can improve visual perception, especially when mental fatigue is low.

## Contribution

The study demonstrates a causal link between tRNS-induced modulation of alpha/beta oscillations and enhanced visual perception in specific brain states.

## Key findings

- tRNS increased HbO amplitude and reduced visual contrast threshold under low fatigue.
- Alpha oscillations showed greater sensitivity to visual perception changes than beta oscillations.
- Fatigue modulates the brain's responsiveness to tRNS in altering sensory processing.

## Abstract

Visual variability is linked to prestimulus alpha (8–13 Hz) and beta (13–30 Hz) power fluctuations, yet their causal role remains unclear. Using transcranial random noise stimulation (tRNS), we tested whether externally modulating cortical excitability could influence these oscillations and alter perception. In a sham-controlled, within-subject design, 29 participants completed a visual detection task combined with electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) recordings. Mental fatigue was modelled as a state-dependent factor. tRNS, primarily under low fatigue, increased online oxyhemoglobin (HbO) amplitude, suppressed offline prestimulus alpha and beta power, and reduced offline visual contrast threshold (VCT), indicating enhanced perception. Further analyses revealed that fatigue influenced the oscillations’ responsiveness to tRNS, and that under low fatigue, alpha power, more than beta, demonstrated greater functional sensitivity to VCT. These findings demonstrate that tRNS can improve perception by modulating alpha/beta oscillations in specific brain states, highlighting the role of brain state in neuromodulation efficacy.

tRNS modulates prestimulus alpha and beta power to enhance visual perception in a state-dependent manner, revealing a causal role of low-frequency oscillations under low fatigue in shaping sensory processing.