Abstract
The contribution of the left inferior prefrontal cortex in semantic processing has been widely investigated in the last decade. Converging evidence from functional imaging studies shows that this region is involved in the “executive” or “controlled” aspects of semantic processing. In this study, we report a single case study of a patient, PW, with damage to the right prefrontal and temporal cortices following stroke. PW showed a problem in executive control of semantic processing, where he could not easily override automatic but irrelevant semantic processing. This case, thus, shows the necessary role of the right inferior prefrontal cortex in executive semantic processing. Compared to tasks previously used in the literature, our tasks placed higher demands on executive semantic processing. We suggest that the right inferior prefrontal cortex is recruited when the demands on executive semantic processing are particularly high.
Highlights
There is an accumulating body of evidence showing that semantic processing is sustained by the temporal lobes, and by prefrontal cortices, especially the left inferior region
PW was presented with semantic judgement tasks in which he was asked to choose among a set of words the one which was related to a cue according to a predefined semantic dimension
As noted in the Introduction, executive semantic processing has mainly been associated with the left inferior prefrontal cortex (e.g., Badre et al, 2005; Cardillo et al, 2004; Demb et al, 1995; Devlin et al, 2003; Metzler, 2001; Moss et al, 2005; Thompson-Schill et al, 1997; Thompson-Schill et al, 1998; Thompson-Schill et al, 1999; Wagner et al, 2000; Wagner et al, 2001; Zhang et al, 2004)
Summary
There is an accumulating body of evidence showing that semantic processing is sustained by the temporal lobes, and by prefrontal cortices, especially the left inferior region (see Fletcher & Henson, 2001, for a review). They found increased activity in the LIPC as the number of words in the choice set increased (from 2 to 4) and as the strength of association between the cue and the target decreased (a target weakly associated to the cue requiring more semantic processing; for similar findings see Bunge, Wendelken, Badre, & Wagner, 2005). Thompson-Schill and colleagues found increased LIPC activity when the semantic task required selecting a task-relevant semantic dimension (Thompson-Schill, D'Esposito, Aguirre, & Farah, 1997; Thompson-Schill, D'Esposito, & Kan, 1999). Increased LIPC activity has been found in a picture naming task, when the item (e.g. the picture of a shark) was preceded by a highly associated distractor (e.g. participant had previously named a “whale” from a verbal description; Moss et al, 2005) or in lexical decision, when the target word was preceded by a semantically incongruent as compared to a semantically congruent context (e.g. “head” preceded by “There was no hair on his...”; Cardillo, Aydelott, Matthews, & Devlin, 2004)
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