Schedule of Events | Symposia

Impact of focal thalamic lesions on task-evoked aperiodic EEG activity

Poster Session A - Saturday, March 29, 2025, 3:00 – 5:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Shannon Stokes¹ (sestokes@uiowa.edu), Neha Nargarkar¹, Boes Aaron¹, Kwang Kai¹; ¹University of Iowa

The goal of this study is to determine the effects of focal thalamic lesions on task-evoked aperiodic slope. Aperiodic activity in EEG recordings may be associated with neural excitation/inhibition(E:I) balance, which can be measured by calculating the slope of the power spectrum. A steeper slope has been interpreted as an increase in inhibition over excitation and vice versa. The neural drivers that change large-scale aperiodic slope properties are relatively understudied. However, converging evidence from anatomical, functional, and lesion studies point to the thalamus being a central subcortical region driving cortex wide E-I balance. This study aims to determine whether a cognitively demanding task can modulate the aperiodic slope and to further investigate whether the human thalamus contributes to this phenomenon using a human lesion study approach. We used the FOOOF algorithm (Donoghue et al., 2020) to extract the aperiodic slope in an EEG dataset from 18 patients with focal brain lesions (5 thalamus, 13 non-thalamus). The patients performed a cognitively demanding hierarchical cognitive control task while EEG data were recorded. We found that in all lesion patients, the aperiodic slope was significantly higher in the task-epoch when compared to baseline. Critically, thalamus lesion patients had a significantly shallower slope in a left temporal cluster of electrodes. These results suggest onset of a task-related stimulus is related to an increase in slope, potentially to promote neural information processing related to cognitive control. Furthermore, we provide unique causal evidence demonstrating that thalamus lesions specifically disrupt task-evoked E:I balance.

Topic Area: EXECUTIVE PROCESSES: Other