Compensatory Augmentation in the Pre-Supplementary Motor Area Mediates Aspects of Verbal Fluency Recovery Following
1Department of Rehabilitation medicine, Chiba-Hokusoh Hospital Nippon medical School, Inzai, Chiba, Japan.
Abstract:
BackgroundCerebellar lesions commonly induce executive dysfunction; however, the underlying neuroplastic mechanisms remain unclear. The fronto-cerebellar diaschisis model, where focal cerebellar damage disrupts widespread frontal networks, offers a compelling hypothesis. Given the pre-supplementary motor area (pre-SMA)'s established role in executive functions, we investigated its specific contribution to post-stroke impairment and its potential function as a dynamic compensatory node during recovery.MethodsWe employed a multimodal approach: resting-state SPECT imaging assessed brain perfusion, and f-NIRS quantified pre-SMA oxygenated hemoglobin ([oxy-Hb]) during a phonemic verbal fluency task (VFT) in 11 patients and 12 age-matched controls. Patients were stratified into Good (N = 6) and Poor (N = 5) recovery subgroups based on VFT performance to isolate the compensatory process. Longitudinal f-NIRS data tracked neural activity changes concurrent with cognitive recovery.ResultsSPECT revealed widespread perfusion abnormalities consistent with diaschisis. Patients exhibited significantly impaired VFT performance. Crucially, the Good Recovery subgroup exhibited a significantly augmented [oxy-Hb] response in the pre-SMA compared to controls, supporting a specific compensatory mechanism. This pre-SMA augmentation was statistically independent of the strong confounding effect of age (F(1,15) = 5.164, P = 0.038). Consistent with a transient compensatory effort, longitudinal data demonstrated a reduction in pre-SMA activity concurrent with subsequent cognitive recovery, suggesting increased neural efficiency.ConclusionsThis study provides preliminary evidence that verbal fluency deficits post-cerebellar stroke are linked to fronto-cerebellar diaschisis. Our findings suggests that the pre-SMA serve as a pivotal compensatory node supporting functional recovery. These results provide a hypothesis-generating basis for future targeted rehabilitation strategies and neuromodulatory interventions.
