Subacute aphasia recovery is associated with resting‐state connectivity within and beyond the language network

Abstract

ObjectiveTo examine changes to connectivity after aphasia treatment in the first 3 months after stroke.MethodsTwenty people experiencing aphasia within the first 3 months of stroke completed MRI before and immediately following 15 hours of language treatment. They were classified based on their response to treatment on a naming test of nouns as either high responders (10% improvement or more), or low responders (<10% improvement). Groups were similar in age, gender distribution, education, days since stroke, stroke volume, and baseline severity. Resting‐state functional connectivity analysis was limited to the connectivity of the left fusiform gyrus with the bilateral inferior frontal gyrus, supramarginal gyrus, angular gyrus, and superior, middle, and inferior temporal gyrus, based on previous studies showing the importance of left fusiform gyrus in naming performance.ResultsBaseline ipsilateral connectivity between the left fusiform gyrus and the language network was similar between high and low responders to therapy when controlling for stroke volume. Following therapy, change in connectivity was significantly greater among high responders between the left fusiform gyrus and the ipsilateral and contralateral pars triangularis, ipsilateral pars opercularis and superior temporal gyrus, and contralateral angular gyrus when compared with low responders.InterpretationAn account of these findings incorporates primarily proximal connectivity restoration, but also potentially reflects select contralateral compensatory reorganization. The latter is often associated with chronic recovery, reflecting the transitional nature of the subacute period.

Remapping and Reconnecting the Language Network after Stroke

“…Treatment was associated with restored connectivity between the left MTG and STG and between the right and left IFG. Connectivity of the right pars triangularis [48] and bidirectionally between the right pars triangularis and left fusiform gyrus [49] have been associated more specifically with recovery of concrete words.…”

Transcranial Direct Current Stimulation to Ameliorate Post-Stroke Cognitive Impairment

“…Studies of tDCS to improve language production in persons with chronic left hemisphere stroke and non-fluent aphasia have revealed positive effects associated with stimulation [ 139 , 140 , 141 , 142 ]. Though functional MRI data suggest that recovery is associated with restoration of the left hemispheric residual language network [ 143 ], other studies suggest that language recovery relies on an intact right hemisphere [ 144 , 145 ]. Therefore, there is no consensus on the optimal target for tDCS for aphasia-related impairments.…”