TRACKING DEEP BRAIN DYNAMICS OF VISUOSPATIAL WORKING MEMORY USING INTRACRANIAL ELECTROENCEPHALOGRAPHY

Visuospatial working memory (VS-WM) enables the short-term retention and manipulation of visual information and relies on interactions across distributed brain networks. While non-invasive studies have mainly characterized cortical dynamics during VS-WM, the contribution of subcortical structures remains difficult to assess. Here, we investigated the neural mechanisms supporting VS-WM using stereoelectroencephalography (SEEG), an intracranial EEG technique employing depth electrodes that enables direct recordings from deep and cortical brain structures, including functionally preserved regions, in 14 neurological patients implanted for clinical evaluation. Participants performed a visuospatial working memory task including distinct retention and manipulation periods. Consistent with previous scalp EEG findings, cortical surface signals showed no sustained task-related modulation during retention, despite preserved behavioral performance. SEEG recordings allowed direct examination of oscillatory activity within deep and cortical regions during task performance. Preliminary analyses revealed sustained theta-band activity within subcortical structures, including the amygdala, cingulum, and hippocampus, during both retention and manipulation periods. At the cortical level, the retention period was associated with increased theta synchronization and beta desynchronization in the orbitofrontal cortex. In contrast, the manipulation period was characterized by alpha-band desynchronization within the temporoparietal junction and the inferior prefrontal cortex Altogether, these preliminary findings indicate that VS-WM engages sustained subcortical theta activity alongside condition-dependent cortical oscillatory dynamics, highlighting the importance of deep brain recordings for capturing neural mechanisms that remain inaccessible to surface electrophysiology.