Stereo-EEG mapping of visual working memory with task-related high-gamma modulations.

Area of Science:

• Neuroscience
• Cognitive Science
• Epileptology

Background:

• Presurgical evaluation for drug-resistant epilepsy necessitates precise mapping of critical cognitive functions.
• Visual working memory (VWM) is a complex cognitive function crucial for daily activities.
• Stereo-electroencephalography (SEEG) offers high spatial resolution for intracranial brain activity monitoring.

Purpose of the Study:

• To introduce a safe, informative, and easily implementable SEEG approach for presurgical VWM mapping.
• To investigate the neural correlates of VWM encoding, retention, recall, and response phases.
• To analyze the impact of VWM-related brain regions on neuropsychological outcomes post-lesioning.

Main Methods:

• Twenty-four epilepsy patients (11-23 years) underwent SEEG monitoring while performing a VWM task.
• High-gamma modulations (HGMs) and weighted phase lag index (wPLI) were analyzed across VWM task phases.
• Correlation between lesion site HGMs and neuropsychological test results was examined.

Main Results:

• The VWM task demonstrated validity through correlations with picture vocabulary scores and response times.
• Distinct patterns of cortical HGMs and neural circuits were identified for each VWM phase (encoding, retention, recall, response).
• Lesioning of sites with high-gamma augmentation negatively impacted VWM-related domains, while suppression affected other cognitive functions.

Conclusions:

• The study extends VWM theoretical models by revealing phase-specific neural subsystem engagement, including the phonological loop and spatial rehearsal.
• Adverse neuropsychological outcomes following VWM site lesioning underscore the clinical significance of presurgical VWM mapping.
• Wider adoption of VWM mapping in presurgical evaluations for drug-resistant epilepsy is recommended.