Decreased Alertness Reconfigures Cognitive Control Networks

Abstract

The normal variability in alertness we experience in daily tasks is rarely taking into account in cognitive neuroscience. Here we studied neurobehavioral dynamics of cognitive control with decreasing alertness. We used the classic Simon Task where participants hear the word "left" or "right" in the right or left ear, eliciting slower responses when the word and the side are incongruent -the conflict effect. Participants performed the task both while fully awake and while getting drowsy, allowing for the characterisation of alertness modulating cognitive control. The changes in the neural signatures of conflict from local theta oscillations to a longdistance distributed theta network suggests a reconfiguration of the underlying neural processes subserving cognitive control when affected by alertness fluctuations.

Decreasing alertness modulates perceptual decision-making

“…A paired samples t-test with t(31) = −7.78, p<0.05 revealed a reliable effect of alertness on reaction times. These behavioural results (Figure 1C) converge with the original findings from Hori (23) indicating slower reaction times under lower levels of alertness, and in agreement to all our previous work (7,18,25–27).…”

“…Transitions of consciousness in the near-awake to light-decrease of alertness is emerging as a model for internally caused interactions (18,26,27,55,56) . With lesion and pharmacological challenges, neuropsychology and cognitive neuroscience have tried to define the necessary and sufficient brain networks, areas and dynamics of the brain to implement cognition, revealing compensation, reconfiguration and plasticity (57)(58)(59) .…”

“…The above studies provide a general overview on the different regions of the brain involved in processes related to decision-making. To explore the question of how alertness modulates these decision-making related processes, we need to first define the specific aspect of wakefulness to be used as the experimental manipulation (17,18) . Alertness related modulations can be classed into 'tonic' fluctuations that span multiple trials and time-periods, and 'phasic' moment to moment modulations in arousal produced in response to an ongoing task.…”

“…We took a computational approach to this problem, validated and automated this procedure to avoid human error, and further cross-validated it to show robust outcomes (24) across different EEG datasets (64, 128 channel) with participants performing a variety of tasks (semantic decision-making, auditory masking). Recently this method was successfully applied to explore the effect of alertness on cognitive control (18) . This sets up the stage for the primary questions that will be analysed in this study: a) In terms of behaviour, how does a perceptual decision making task get affected by changing levels of tonic alertness.…”

Preserved sensory processing but hampered conflict detection when stimulus input is task-irrelevant

“…the word “left” from the right speaker) but not on others (e.g. the word “right” from the right speaker) (Buzzell et al, 2013; Canales-Johnson et al, 2020). A wealth of previous studies has revealed that conflict arises between task-relevant and task-irrelevant features of the stimulus in these type of tasks (similar to the Simon task and Stroop task, Egner & Hirsch, 2005; Hommel, 2011).…”