Refractory effects in stroke aphasia: A consequence of poor semantic control

Distinct loci of lexical and semantic access deficits in aphasia: Evidence from voxel-based lesion-symptom mapping and diffusion tensor imaging

“…A number of neuropsychological studies demonstrate that patients with aphasia show exaggerated semantic interference when naming (Biegler et al, 2008;McCarthy & Kartsounis, 2000;Schnur, Schwartz, Brecher, & Hodgson, 2006;Schnur et al, 2009;Wilshire & McCarthy, 2002) and comprehending semantically related stimuli (Campanella, Crescentini, Mussoni, & Skrap, 2013;Forde & Humphreys, 1995Gardner et al, 2012;Jefferies et al, 2007; M A N U S C R I P T…”

“…First, patients with aphasia often make more errors in the related compared to unrelated contexts in naming (McCarthy & Kartsounis, 2000;Schnur et al, 2005;Wilshire & McCarthy, 2002) and comprehension (Crutch & Warrington, 2005;Jefferies et al, 2007;Warrington & Cipolotti, 1996, Experiment 4) variants of the task (henceforth, relatedness effect). This is thought to reflect an impairment in accessing the representations themselves (i.e., lexical or semantic; see Figure 1) where damage creates noisy activation of representations, making them difficult to distinguish from one another in semantically blocked sets of trials.…”

“…2000; Warrington & Cipolotti, 1996), and/or damage to a cognitive control mechanism involved in resolving interference (Biegler et al, 2008;Jefferies et al, 2007;Schnur et al, 2006Schnur et al, , 2009.…”

“…This cognitive control mechanism is likely subserved by the left inferior frontal gyrus (LIFG), a region located within the left inferior prefrontal cortex that when damaged impedes competition resolution over lexical and semantic representations (see Novick, Trueswell, & Thompson-Schill, 2010 for a review). However, in Jefferies et al (2007), the size of the patient group was small, as only four patients could perform both production and M A N U S C R I P T NEURAL SUBSTRATES OF SEMANTIC INTERFERENCE 12 comprehension tasks, and the reported increasing relatedness effect was weak or non-significant across the group (see Gardner et al, 2012, p. 781 for a similar discussion). Further, because some studies investigating semantic context effects using cyclical tasks -either in production or comprehension -did not contrast performance across cycles of related items with that of a baseline measure of performance (i.e., an unrelated condition; e.g., Jefferies et al, 2007;McCarthy & Kartsounis, 2000, Test 4a;Hamilton & Martin, 2010;Warrington & Cipolotti, 1996), it is unclear whether increasingly worse performance across cycles reflects a true impairment in cognitive control or a refractory effect that affects repeatedly accessing the same stimuli more generally (for evidence of increasingly worse performance when repeatedly naming unrelated items see McCarthy & Kartsounis, 2000, Test 1).…”

“…Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Further, damage to the left inferior frontal gyrus (LIFG), a region implicated in cognitive control, results in increasing semantic interference when items repeat across cycles in both language production and comprehension (Jefferies, Baker, Doran, & Lambon Ralph, 2007). This generates the prediction that the LIFG via white matter connections supports resolution of semantic interference arising from different loci (lexical vs. semantic) in the temporal lobe.…”