Publication Date
12-28-2024
Journal
Scientific Reports
DOI
10.1038/s41598-024-80911-3
PMID
39730513
PMCID
PMC11681213
PubMedCentral® Posted Date
12-28-2024
PubMedCentral® Full Text Version
Post-print
Published Open-Access
yes
Keywords
Humans, Auditory Cortex, Male, Female, Adult, Acoustic Stimulation, Pupil, Evoked Potentials, Auditory, Young Adult, Electroencephalography, Middle Aged, Aperiodic activity, 1/f slope, Arousal state, Pupil diameter, Auditory cortex, Human iEEG, Sensory processing, Neurophysiology
Abstract
Alteration of responses to salient stimuli occurs in a wide range of brain disorders and may be rooted in pathophysiological brain state dynamics. Specifically, tonic and phasic modes of activity in the reticular activating system (RAS) influence, and are influenced by, salient stimuli, respectively. The RAS influences the spectral characteristics of activity in the neocortex, shifting the balance between low- and high-frequency fluctuations. Aperiodic '1/f slope' has emerged as a promising composite measure of these brain state dynamics. However, the relationship of 1/f slope to state-dependent processes, such as saliency, is less explored, particularly intracranially in humans. Here, we record pupil diameter as a measure of brain state and intracranial local field potentials in auditory cortical regions of human patients during an auditory oddball stimulus paradigm. We find that phasic high-gamma band responses in auditory cortical regions exhibit an inverted-u shaped relationship to tonic state, as reflected in the 1/f slope. Furthermore, salient stimuli trigger state changes, as indicated by shifts in the 1/f slope. Taken together, these findings suggest that 1/f slope tracks tonic and phasic arousal state dynamics in the human brain, increasing the interpretability of this metric and supporting it as a potential biomarker in brain disorders.