Cerebellar activity switches hemispheres with cerebral recovery in aphasia.
The right postero-lateral cerebellum participates with the left frontal lobe in the selection and production of words. Using fMRI, we examined whether cerebellar activity switches hemispheres in parallel with recruitment of putative compensatory right homologous frontal regions in post-stroke aphasia. Re-examining the data of Blasi et al. [Blasi, V., Young, A. C., Tansy, A. P., Petersen, S. E., Snyder, A. Z., & Corbetta, M. (2002). Word retrieval learning modulates right frontal cortex in patients with left frontal damage. Neuron, 36(1), 159-170], we asked: (1) if activity in the right cerebellum was disrupted by a left frontal lesion, (2) if activity switched to the left cerebellum, and (3) if activity in the left cerebellum was modulated by learning, as was right frontal cortex. Fourteen age-matched controls and eight mildly aphasic stroke patients participated. Aphasic participants all had lesions due to unilateral left hemisphere stroke at or near Broca's area. Subjects silently performed a word stem completion task with either novel or repeated items. Activity in right cerebellum of aphasic individuals was minimal and was not modulated by learning, as for controls. However, we observed robust learning-related attenuation of the BOLD signal in the left postero-lateral cerebellum consistent with learning-related effects in right frontal cortex. These findings support the hypothesis that right frontal and left cerebellar circuits are likely to be functionally relevant to recovered/residual verbal function.
Connor
Lisa Tabor
LT
Department of Radiology, Box 8225, Washington University School of Medicine, 4525 Scott Avenue, St. Louis, MO 63110, USA, and Neuroradiology Institute, San Raffaele Hospital, Milan, Italy. lconnor@npg.wustl.edu
DeShazo Braby
Tiffany
T
Snyder
Abraham Z
AZ
Lewis
Christopher
C
Blasi
Valeria
V
Corbetta
Maurizio
M
D000328:Adult; D001037:Aphasia / Q000209:etiology / Q000503:physiopathology*; D001931:Brain Mapping; D002531:Cerebellum / Q000502:physiology*; D005625:Frontal Lobe / Q000502:physiology / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D016555:Matched-Pair Analysis; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology; D011930:Reaction Time; D020127:Recovery of Function / Q000502:physiology*; D012016:Reference Values; D020521:Stroke / Q000150:complications / Q000503:physiopathology; D014706:Verbal Learning / Q000502:physiology*