Characterising time-on-task effects on oscillatory and aperiodic EEG components and their co-variation with visual...

Area of Science:

• Neuroscience
• Cognitive Psychology
• Computational Neuroscience

Background:

• Brain-behavior relationships are often assumed to stem from random neural fluctuations.
• However, systematic trends with time on task can affect both brain activity and performance metrics like response speed.

Purpose of the Study:

• To investigate if time-on-task trends explain relationships between oscillatory brain activity and behavioral performance (speed, accuracy, confidence).
• To differentiate alpha-band brain-behavior links that are explained by time-on-task from those that persist after accounting for it.

Main Methods:

• Thirty-six participants completed a visual discrimination task with confidence ratings over 900 trials.
• Electroencephalography (EEG) spectral power (1-40 Hz) and aperiodic components were analyzed across experimental blocks.
• Time-on-task effects on EEG were related to single-trial behavioral measures.

Main Results:

• Time-on-task increased alpha power and decreased peak alpha frequency, even after controlling for aperiodic activity.
• These time-on-task effects in alpha activity significantly explained reaction time variability.
• Controlling for time-on-task eliminated the observed relationships between alpha activity and reaction times.
• Time-on-task did not impact other EEG signatures related to decision confidence.

Conclusions:

• Time-on-task systematically alters alpha-band EEG activity.
• Observed brain-behavior relationships in the alpha band are often artifacts of time-on-task effects.
• Accounting for time-on-task is essential for accurately interpreting the functional role of alpha oscillations in visual perception.