An Essential Role of the Intraparietal Sulcus in Response Inhibition Predicted by Parcellation-Based Network.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• The posterior parietal cortex (PPC) has known connections with the prefrontal cortex, but its necessity in executive functions remains debated.
• Previous lesion studies have questioned the role of the PPC in executive functions, prompting further investigation into specific subregions.

Purpose of the Study:

• To investigate the necessity of the posterior parietal cortex (PPC) in executive functions, specifically response inhibition.
• To identify a candidate PPC region essential for response inhibition using functional MRI and parcellation-based network analysis.
• To confirm the essential role of the identified region in response inhibition using transcranial magnetic stimulation (TMS).

Main Methods:

• Utilized the stop-signal task to assess response inhibition.
• Measured brain activity and resting-state functional connectivity using functional MRI (fMRI) with parcellation-based network analysis.
• Applied transcranial magnetic stimulation (TMS) over the intraparietal sulcus (IPS) and temporoparietal junction (TPJ) to test causal roles.

Main Results:

• The intraparietal sulcus (IPS) was activated during response inhibition and showed functional connectivity with key frontal regions (inferior frontal cortex, presupplementary motor area).
• TMS over the IPS significantly prolonged stop-signal reaction time (SSRT), indicating impaired response inhibition.
• TMS over the temporoparietal junction (TPJ) did not affect SSRT, despite its activation during the task.

Conclusions:

• The intraparietal sulcus (IPS), identified via parcellation-based network analysis, plays an essential role in response inhibition.
• These findings challenge previous views and highlight the critical involvement of the IPS within the posterior parietal cortex in executive functions.
• The study provides causal evidence for the IPS's necessity in controlling prepotent responses.