Affiliations: University of Pennsylvania, Department of Psychology, Center for Cognitive Neuroscience, Philadelphia, PA, USA | University of Pennsylvania, Department of Neurology, Center for Cognitive Neuroscience, Philadelphia, PA, USA | University of Pennsylvania, Laboratory for Cognition and Neural Stimulation, Philadelphia, PA, USA
Note: [] Corresponding author: Roy H. Hamilton, MD, MS., 3710 Hamilton Walk, Goddard Laboratories, Room 518, PA, USA. Tel.: +215 573 7065; Fax: +215 573 7136; E-mail: Roy.Hamilton@uphs.upenn.edu
Abstract: Aphasia is a common consequence of unilateral stroke, typically involving perisylvian regions of the left hemisphere. The course of recovery from aphasia after stroke is variable, and relies on the emergence of neuroplastic changes in language networks. Recent evidence suggests that rehabilitation interventions may facilitate these changes. Functional reorganization of language networks following left-hemisphere stroke and aphasia has been proposed to involve multiple mechanisms, including intrahemispheric recruitment of perilesional left-hemisphere regions and transcallosal interhemispheric interactions between lesioned left-hemisphere language areas and homologous regions in the right hemisphere. Moreover, it is debated whether interhemispheric interactions are beneficial or deleterious to recovering language networks. Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are two safe and noninvasive procedures that can be applied clinically to modulate cortical excitability during poststroke language recovery. Intervention with these noninvasive brain stimulation techniques also allows for inferences to be made regarding mechanisms of recovery, including the role of intrahemispheric and interhemispheric interactions. Here we review recent evidence that suggests that TMS and tDCS are promising tools for facilitating language recovery in aphasic patients, and examine evidence that indicates that both right and left hemisphere mechanisms of plasticity are instrumental in aphasia recovery.
Keywords: Aphasia, stroke, neuroplasticity, transcranial magnetic stimulation, transcranial direct current stimulation, neurorehabilitation, interhemispheric interactions
