Abstract
IntroductionThe mechanism of functional recovery in right hemisphere (RH) stroke patients when attempting to comprehend a proverb has not been identified. We previously reported that there is bilateral hemisphere involvement during proverb comprehension in the normal population. However, the underlying mechanisms of proverb comprehension following a right middle cerebral artery (MCA) infarction have not yet been fully elucidated.MethodsWe here compared the brain regions activated by literal sentences and by opaque or transparent proverbs in right MCA infarction patients using functional magnetic resonance imaging (fMRI). Experimental stimuli included 18 opaque proverbs, 18 transparent proverbs, and 18 literal sentences that were presented pseudorandomly in 1 of 3 predesigned sequences.ResultsFifteen normal adults and 17 right MCA infarction patients participated in this study. The areas of the brain in the stroke patients involved in understanding a proverb compared with a literal sentence included the right middle frontal gyrus (MFG) and frontal pole, right anterior cingulate gyrus/paracingulate gyrus and left inferior frontal gyrus (IFG), middle temporal gyrus (MTG), precuneus, and supramarginal gyrus (SMG). When the proverbs were presented to these stroke patients in the comprehension tests, the left supramarginal, postcentral gyrus, and right paracingulate gyrus were activated for the opaque proverbs compared to the transparent proverbs.ConclusionsThese findings suggest that the functional recovery of language in stroke patients can be explained by perilesional activation, which is thought to arise from the regulation of the excitatory and inhibitory neurotransmitter system, and by homotopic area activation which has been characterized by decreased transcallosal inhibition and astrocyte involvement.
Highlights
The mechanism of functional recovery in right hemisphere (RH) stroke patients when attempting to comprehend a proverb has not been identified
When compared with the activated regions in the normal subjects following the proverb comprehension testing, we found that the right middle frontal gyrus and frontal pole, right anterior cingulate gyrus/paracingulate gyrus and left inferior frontal gyrus (IFG), middle temporal gyrus (MTG), precuneus, and supramar‐ ginal gyrus (SMG) were more activated in the stroke patients (Table 5, Figure 2)
We found that the left SMG, middle frontal gyrus (MFG), and central opercular cortex were more activated in the stroke patients than in the normal con‐ trol subjects following the opaque proverb comprehension testing, as were the left IFG and MTG following the transparent proverb comprehension
Summary
There has been considerable debate on whether the right hemi‐ sphere (RH) is involved in understanding figurative language in nor‐ mal subjects (Bookheimer, 2002; Bottini et al, 1994; Diaz, Barrett, & Hogstrom, 2011; Faust & Mashal, 2007; Kana, Murdaugh, Wolfe, & Kumar, 2012; Lai, Dam, Conant, Binder, & Desai, 2015; Lee & Dapretto, 2006; Mashal, Faust, & Hendler, 2005; Mitchell, Vidaki, & Lavidor, 2016; Oliveri, Romero, & Papagno, 2004; Papagno, Curti, Rizzo, Crippa, & Colombo, 2006; Proverbio, Crotti, Zani, & Adorni, 2009; Yang et al, 2016; Zempleni, Haverkort, Renken, & Stowe, 2007). It has recently been shown that RH activation can be influenced by various factors such as conventionality at either a word‐level or in a sentential context, by task type, and by the level of transparency (Anaki, Faust, & Kravetz, 1998; Diaz et al, 2011; Faust & Chiarello, 1998; Faust & Mashal, 2007; Mashal et al, 2005; Rapp, Mutschler, & Erb, 2012; Schmidt & Seger, 2009; Sela, Panzer, & Lavidor, 2017; Yang et al, 2016) It has been demonstrated previ‐ ously that metaphoric comprehension involves an enhanced role of the right hemisphere in accordance with hemispheric semantic pro‐ cessing (Anaki et al, 1998). We specu‐ lated that another part of the brain would be activated and involved in abstract processing in these stroke patients than the right SMG and precuneus that is seen in normal subjects
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