Action-related dynamic changes in inferior frontal cortex effective connectivity: A TMS/EEG coregistration study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Motor Control

Background:

• The inferior frontal cortex (IFC) is crucial for visually guided finger movements.
• Understanding the dynamic connectivity of the IFC during action execution is limited.

Purpose of the Study:

• To investigate how the IFC's effective connectivity changes during a visuomotor task.
• To map the temporal dynamics of IFC interactions with other brain regions.

Main Methods:

• Utilized single-pulse transcranial magnetic stimulation (TMS) combined with simultaneous electroencephalography (EEG) recording (TMS-EEG).
• Stimulated the left posterior IFC during rest and a visuomotor task, recording TMS-evoked potentials (TEPs).
• Localized TEP sources using standardized low-resolution brain electromagnetic tomography (sLORETA).

Main Results:

• TEPs showed significant modulation by task conditions at ~60 and ~80 milliseconds post-stimulation.
• At ~60 ms, IFC connectivity increased with fronto-parietal motor areas and decreased with occipito-temporal visual areas.
• At ~80 ms, TEPs increased in regions overlapping with the default-mode network, suggesting its inhibition.

Conclusions:

• Demonstrated dynamic, time-dependent changes in IFC effective connectivity during visuomotor tasks.
• These findings suggest sequential stages of action control, sensory processing, and default-mode network suppression by the IFC.
• Results provide new insights into the neural mechanisms underlying versatile finger movements.