Distinct mechanisms and timing of language recovery after stroke

The "language network" is remarkably stable across language tasks but changes in response to injury to specific components or in response to "disconnection" of input to one component. We investigated network changes during language recovery, hypothesizing that language recovery takes place through distinct mechanisms: (a) reperfusion; (b) recovery from diaschisis; (c) recovery from structural disconnection; and (d) "reorganization" of language, whereby various components assume function of a damaged component. We also tested the hypothesis that "reorganization" depends on: the language task, level of performance, size and site of stroke, and time post onset. We tested these hypotheses in five participants who had structural, perfusion, and functional imaging utilizing spelling, reading, word generation, and picture naming tasks at acute and subsequent stages after ischaemic stroke. These cases illustrate different mechanisms of aphasia recovery or illustrate that reorganization of language acutely depends on individual variables in addition to size and site of stroke.