Subjective Cognitive Effort Indexes Sub-Criticality in the Brain

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Project Summary / Abstract Cognitive effort is subjectively costly. It can cause people to discount valuable goals and avoid thoughtful planning and careful deliberation. Effort avoidance can thus be problematic, especially in disorders like depression and schizophrenia where excessive cost sensitivity undermines cognitive motivation. To address cost sensitivity, we first need to understand what the brain treats as costly. Traditional indices, like lateral frontal fMRI signals, and parietal alpha desynchronization in EEG data, track cognitive load to a point, but often plateau or decline, even when subjective effort continues to rise. This project will examine a promising candidate metric of cognitive effort: criticality suppression. Criticality characterizes cortical dynamics at rest, and prior studies have shown that brains becomes increasingly sub-critical under the very conditions known to increase subjective effort: increasing working memory load, fatigue, sleep deprivation, novelty, and cognitive aging. In Aim 1, criticality suppression will be monitored with EEG, and compared to behavioral economic measures of subjective effort costs both across individuals (capturing individual differences in cost sensitivity) and within individuals (capturing cost sensitivity across load levels). In Aim 2, TMS will be used to test whether modulating criticality (artificially) impacts sensitivity to effort costs, apart from cognitive demands. Finally, in Aim 3, concurrent TMS- EEG will be used to investigate the mechanisms regulating criticality. In particular, Aim 3 will test the hypothesis that the cortical excitatory-inhibitory balance regulates how closely to a critical state the brain operates, and thereby how sensitive people are to effort costs. Aims 1 and 2 will thus provide the applicant with essential training in EEG and TMS methodologies while testing a novel hypothesis linking criticality to subjective cognitive effort. Subsequently, in the applicant’s independent phase, Aim 3 will combine and apply these methodologies to test hypothesized mechanisms which may underlie cognitive effort, working memory, and cognitive motivation.