J Neurosci. 2024 Aug 21:e2308232024. doi: 10.1523/JNEUROSCI.2308-23.2024. Online ahead of print.

ABSTRACT

The human brain exhibits both oscillatory and aperiodic, or 1/f, activity. Although a large body of research has focused on the relationship between brain rhythms and sensory processes, aperiodic activity has often been overlooked as functionally irrelevant. Prompted by recent findings linking aperiodic activity to the balance between neural excitation and inhibition, we investigated its effects on the temporal resolution of perception. We recorded EEG from participants (both sexes) during resting state and a task in which they detected the presence of two flashes separated by variable inter-stimulus intervals. Two-flash discrimination accuracy typically follows a sigmoid function whose steepness reflects perceptual variability or inconsistent integration/segregation of the stimuli. We found that individual differences in the steepness of the psychometric function correlated with EEG aperiodic exponents over posterior scalp sites. In other words, participants with flatter EEG spectra (i.e., greater neural excitation) exhibited increased sensory noise, resulting in shallower psychometric curves. Our finding suggest that aperiodic EEG is linked to sensory integration processes usually attributed to the rhythmic inhibition of neural oscillations. Overall, this correspondence between aperiodic neural excitation and behavioral measures of sensory noise provides a more comprehensive explanation of the relationship between brain activity and sensory integration and represents an important extension to theories of how the brain samples sensory input over time.Significance statement Neural oscillations are fundamental for temporal organization and communication of information in the brain, while irregular activity has been suggested to disrupt these processes.We investigated the impact of aperiodic electrophysiological activity on a visual integration task known to depend on rhythmic brain organization. Crucially, Individuals exhibiting higher 1/f electrophysiological noise showed increased uncertainty or perceptual noise in temporal perception, highlighting how irregular neural activity affects tasks relying on periodic neural organization. These findings significantly advance our understanding of aperiodic EEG and its implications for perception, shedding light on its intricate interplay with various neural processes.

PMID:39168653 | DOI:10.1523/JNEUROSCI.2308-23.2024