When "Crack walnuts" lies in different brain regions: evidence from a voxel-based lesion-symptom mapping study

Theories of lexical processing differ as to how multimorphemic words, such as compounds, are mentally processed. The most recent findings seem to support the dual route hypothesis, which assumes that complex words can be stored and retrieved either whole or by decomposition into their constituents. Despite great efforts to investigate the cognitive mechanisms involved in processing complex words, very little is known about how compounds are represented in the brain. The present study was designed to address this issue in a group of 20 left-hemispheric stroke patients who were submitted to four picture-naming tasks involving nouns, verbs, noun-noun (NN) and verb-noun (VN) compounds. To determine the brain lesions implicated in these tasks, we analyzed patients' performances together with their lesions using Voxel-based Lesion Symptom Mapping (VLSM). Results showed that while NN involved the same temporal areas as nouns, VN (although they belong to the noun category) involved different fronto-temporal regions. This latter finding is discussed within the view that distinct mechanisms process the different constituents of complex words.