Temporal dynamics of TMS interference over preparatory alpha activity during semantic decisions.

Area of Science:

• Neuroscience
• Cognitive Electrophysiology
• Brain Stimulation

Background:

• EEG alpha (8-12 Hz) power desynchronization (ERD) is a key indicator of task anticipation.
• Anticipatory alpha ERD typically increases and peaks before target stimulus presentation in fixed cue-target interval paradigms.
• Previous research indicates that magnetic stimulation can modulate anticipatory alpha ERD over specific cortical regions.

Purpose of the Study:

• To investigate the temporal dynamics of anticipatory alpha ERD.
• To determine if magnetic stimulation generally attenuates or interrupts the typical development of alpha ERD.
• To examine the causal role of the left angular gyrus (AG) in semantic decision task anticipation.

Main Methods:

• Participants performed a semantic decision task.
• Repetitive transcranial magnetic stimulation (rTMS) was applied over the left AG, left inferior parietal sulcus (IPS), or sham condition.
• EEG was recorded to measure alpha ERD amplitude and temporal dynamics.

Main Results:

• rTMS over the left AG significantly shortened the peak latency and decreased the peak amplitude of anticipatory alpha ERD compared to active (left IPS) and sham TMS.
• The effects were observed during a semantic decision task.
• These findings suggest a disruption of the typical temporal evolution of alpha ERD.

Conclusions:

• The left AG plays a causal role in the anticipation of semantic decision tasks.
• Magnetic stimulation, specifically rTMS over the left AG, not only reduces mean anticipatory alpha ERD amplitude but also interrupts its temporal development.
• These results highlight the complex interplay between cortical stimulation and the temporal dynamics of cognitive anticipation.