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Where language meets meaningful action: a combined behavior and lesion analysis of aphasia and apraxia

It is debated how language and praxis are co-represented in the left hemisphere (LH). As voxel-based lesion symptom mapping in LH stroke patients with aphasia and/or apraxia may contribute to this debate, we here investigated the relationship between language and praxis deficits at the behavioral and lesion levels in 50 sub-acute stroke patients. We hypothesized that language and (meaningful) action are linked via semantic processing in Broca’s region.
Behaviorally, half of the patients suffered from co-morbid aphasia and apraxia. While 24% (n=12) of all patients exhibited aphasia without apraxia, apraxia without aphasia was rare (n=2, 4%). Left inferior frontal, insular, inferior parietal and superior temporal lesions were specifically associated with deficits in naming, reading, writing, or auditory comprehension. In contrast, lesions affecting the left inferior frontal gyrus, premotor cortex and the central region as well as the inferior parietal lobe were associated with apraxic deficits (i.e., pantomime, imitation of meaningful and meaningless gestures). Thus, contrary to the predictions of the embodied cognition theory, lesions to sensorimotor and premotor areas were associated with the severity of praxis but not language deficits.
Lesions of Brodmann area (BA) 44 led to combined apraxic and aphasic deficits. Data suggest that BA 44 acts as an interface between language and (meaningful) action thereby supporting parcellation schemes (based on connectivity and receptor mapping) which revealed a BA 44 sub-area involved in semantic processing.

Weiss 2014

Relationship of the specific lesion correlate of combined aphasic and apraxic deficits with the cytoarchitectonically defined Brodmann areas 44 and 45
A. Lateral view on the rendered left hemisphere of the MNI template brain provided by MRIcron depicting cytoarchitectonically defined Broca’s region based on the maximum probability maps (MPMs) of Brodmann areas (BA) 44 (red) and 45 (green).
B. Depiction of the correspondence between the (macro-anatomical) landmarks of Broca’s region (i.e., pars opercularis and triangularis of the inferior frontal gyrus, IFG) and the specific lesion correlate of combined aphasic and apraxic deficits derived from the VLSM analyses (yellow), the anterior-ventral cluster 3 of Brodmann area (BA) 44 based on connectivity analyses (blue) as well as the maximum probability maps (MPMs) of BA 44 (red) and BA 45 (green) based on cytoarchitecture. Note that the cluster 3 of BA 44 forms - by definition - the anterior-ventral border of BA 44, i.e., this cluster borders on BA 45 (compare Figures 5A and B).

Publication

Weiss PH, Ubben SD, Kaesberg S, Kalbe E, Kessler J, Liebig T, Fink GR (2014) Where language meets meaningful action: a combined behavior and lesion analysis of aphasia and apraxia. Brain, Structure and Function (in press: doi 10.1007/s00429-014-0925-3).


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