Prestimulus EEG alpha oscillations modulate task-related fMRI BOLD responses to auditory stimuli

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• Electroencephalography (EEG) alpha-band activity is traditionally linked to inhibition and reduced attention.
• A competing theory posits alpha oscillations actively process relevant information, involving phase dynamics.
• Understanding the precise role of alpha oscillations (power vs. phase) in cognitive tasks remains debated.

Purpose of the Study:

• To investigate the impact of prestimulus alpha-band activity on brain responses during an auditory oddball task.
• To differentiate the effects of alpha power and phase on task-relevant and decision-related processing.
• To reconcile conflicting hypotheses regarding the function of alpha oscillations.

Main Methods:

• Simultaneous electroencephalography (EEG) and functional Magnetic Resonance Imaging (fMRI) were employed.
• Whole-brain analysis was conducted to examine event-related BOLD responses.
• Posterior alpha rhythm's power and phase were analyzed separately.

Main Results:

• Increased prestimulus alpha power correlated with heightened BOLD activity in late processing areas related to decision-making.
• No significant effect of alpha power was observed in primary sensory regions.
• Alpha phase analysis revealed correlations in the bilateral thalamus, suggesting early modulation of sensory processing.

Conclusions:

• Cortical alpha rhythm acts as a cyclic modulator of task-related responses, particularly early in the processing stream via thalamo-cortical loops.
• Alpha power influences higher-level decision-making processes.
• Findings support an active role for alpha oscillations, integrating both inhibition and active processing mechanisms.