EEG phase states at stimulus onset in a variable-ISI Go/NoGo task: Effects on ERP components

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Psychology

Background:

• Previous electroencephalography (EEG) studies identified non-random EEG phases at stimulus onset influencing event-related potentials (ERPs) in fixed interstimulus interval (ISI) tasks.
• These phase effects were substantial, impacting ERP components significantly.

Purpose of the Study:

• To investigate the impact of prestimulus EEG phase on cognitive processing in a variable ISI auditory Go/NoGo task.
• To reduce or prevent preferential phase occurrence by employing a variable ISI.

Main Methods:

• Utilized discrete Fourier transforms to analyze prestimulus EEG phase at Cz for delta, theta, alpha, and beta bands.
• Sorted trials into phase quartiles and examined ERPs using temporal Principal Component Analyses (PCAs).

Main Results:

• Preferential phase occurrence was reduced in the variable ISI task as predicted.
• Random EEG phases at stimulus onset significantly impacted ERP component amplitudes.
• Delta band negativity enhanced both Go and NoGo P3b components; theta band negativity reduced NoGo P3b but not Go P3b.

Conclusions:

• Prestimulus EEG phase at stimulus onset plays a crucial role in differential cognitive processing during two-choice tasks.
• The findings suggest that the brain's state, as reflected by EEG phase, influences how stimuli are processed.
• Variable ISI tasks offer a method to study the effects of random phase on cognitive processing.