Cooperative processing in primary somatosensory cortex and posterior parietal cortex during tactile working memory

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Sensory Processing

Background:

• Working memory (WM) is essential for temporary information storage and manipulation.
• The roles of the primary somatosensory cortex (SI) and posterior parietal cortex (PPC) in tactile unimodal WM are not fully understood.
• Understanding brain regions involved in tactile WM is key to deciphering sensory processing mechanisms.

Purpose of the Study:

• To investigate the causal roles of the primary somatosensory cortex (SI) and posterior parietal cortex (PPC) in a tactile unimodal working memory task.
• To determine if these brain regions process tactile information cooperatively or sequentially.
• To compare tactile unimodal WM processing with tactile-visual cross-modal WM.

Main Methods:

• Utilized single-pulse transcranial magnetic stimulation (spTMS) targeting left SI (ipsilateral), right SI (contralateral), and right PPC (contralateral).
• Participants performed a tactile-tactile unimodal delayed matching-to-sample task.
• spTMS was applied at 300, 600, and 900 ms after sample stimulus onset.

Main Results:

• Disrupting either contralateral SI or contralateral PPC significantly impaired task accuracy compared to ipsilateral SI stimulation.
• Performance degradation was consistent across all tested time points (300, 600, 900 ms).
• Ipsilateral SI stimulation showed less impact on accuracy, suggesting hemispheric specialization.

Conclusions:

• The primary somatosensory cortex (SI) and posterior parietal cortex (PPC) cooperatively process tactile information within the same hemisphere during unimodal WM.
• This cooperative processing begins in the early delay phase of the tactile unimodal WM task.
• Tactile unimodal WM processing differs from tactile-visual cross-modal WM, where SI and PPC contribute sequentially, indicating intermodal information transfer.