Brain Advance Access published online on November 10, 2009
Brain, doi:10.1093/brain/awp270
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Anterior temporal lobe connectivity correlates with functional outcome after aphasic stroke
1 Department of Clinical Neuroscience, Division of Neuroscience and Mental Health, Hammersmith Hospital Campus, Imperial College London, London W12 0NN, UK 2 Cognitive Neuroimaging Group, MRC Clinical Sciences Centre, Hammersmith Hospital, London W12 0NN, UK 3 Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, UK 4 Neuroscience and Aphasia Research Unit (NARU), School of Psychological Sciences, University of Manchester, Manchester M13 9PL, UK
Correspondence to:
Dr Jane Warren, Cognitive Neuroimaging Group, MRC Cyclotron Unit, Hammersmith Hospital, London W12 0NN, UK E-mail: jane.warren{at}imperial.ac.uk
Focal brain lesions are assumed to produce language deficits by two basic mechanisms: local cortical dysfunction at the lesion site, and remote cortical dysfunction due to disruption of the transfer and integration of information between connected brain regions. However, functional imaging studies investigating language outcome after aphasic stroke have tended to focus only on the role of local cortical function. In this positron emission tomography functional imaging study, we explored relationships between language comprehension performance after aphasic stroke and the functional connectivity of a key speech-processing region in left anterolateral superior temporal cortex anterolateral superior temporal cortex. We compared the organization of left anterolateral superior temporal cortex functional connections during narrative speech comprehension in normal subjects with left anterolateral superior temporal cortex connectivity in a group of chronic aphasic stroke patients. We then evaluated the language deficits associated with altered left anterolateral superior temporal cortex connectivity in aphasic stroke. During normal narrative speech comprehension, left anterolateral superior temporal cortex displayed positive functional connections with left anterior basal temporal cortex, left inferior frontal gyrus and homotopic cortex in right anterolateral superior temporal cortex. As a group, aphasic patients demonstrated a selective disruption of the normal functional connection between left and right anterolateral superior temporal cortices. We observed that deficits in auditory single word and sentence comprehension correlated both with the degree of disruption of left-right anterolateral superior temporal cortical connectivity and with local activation in the anterolateral superior temporal cortex. Subgroup analysis revealed that aphasic patients with preserved positive intertemporal connectivity displayed better receptive language function; these patients also showed greater than normal left inferior frontal gyrus activity, suggesting a possible top-down compensatory mechanism. These results demonstrate that functional connectivity between anterolateral superior temporal cortex and right anterior superior temporal cortex is a marker of receptive language outcome after aphasic stroke, and illustrate that language system organization after focal brain lesions may be marked by complex signatures of altered local and pathway-level function.
Key Words: aphasia; post-stroke recovery; functional neuroimaging; neural networks; anterior temporal lobe
Abbreviations: BTC, basal temporal cortex; IFG, inferior frontal gyrus; LaBTC, left anterior fusiform gyrus region of interest; LalSTC, left anterolateral STC region of interest; LIFG, left IFG pars triangularis region of interest; MNI, Montreal Neurological Institute; RalSTC, right anterior superior temporal gyrus and suslcus region of interest; SPM, statistical parametric mapping; STC, superior temporal cortex
Received March 5, 2009. Revised July 30, 2009. Accepted September 3, 2009.