The neural basis of metaphor comprehension: evidence from left hemisphere degeneration

Abstract

<p>Despite the ubiquity of metaphor in cognition and communication, it is absent from standard clinical assessments of language, and the neural systems that support metaphor processing are debated. Previous research shows that patients with focal brain lesions can display selective impairments in processing metaphor, suggesting that figurative language abilities may be disproportionately vulnerable to brain injury. We hypothesized that metaphor processing is especially vulnerable to neurodegenerative disease, and that the left hemisphere is critical for normal metaphor processing. To evaluate these hypotheses, we tested metaphor comprehension in patients with left-hemisphere neurodegeneration (LHND), and in demographically- matched healthy control subjects (HC). Stimuli consisted of moderately-familiar metaphors and closely matched literal sentences sharing the same source term (The interview was a painful crawl/ The infant’s motion was a crawl). Written sentences were presented, followed by four modifier-noun answer choices (one target and three foils). HC, though reliably better at literal than metaphor trials, comprehended both sentence conditions well. By contrast, LHND participants performed disproportionately poorly on metaphor comprehension. Anatomical analyses show relationships between metaphor accuracy and patient atrophy in left middle and superior temporal gyri, and the left inferior frontal gyrus, areas that have been implicated in supporting metaphor comprehension in previous imaging research. The behavioral results also suggest deficits of metaphor comprehension may be a sensitive measure of cognitive dysfunction in some forms of neurodegenerative disease.</p>

Non-literal language processing is jointly supported by the language and Theory of Mind networks: Evidence from a novel meta-analytic fMRI approach

“…In contrast, RH damage, which does not strongly affect basic language processing, may make apparent more subtle linguistic impairments, leading to the apparent RH bias for non-literal comprehension. In line with this possibility, several studies have reported that patients with LH damage show similar, or even greater, deficits in non-literal comprehension compared to RH-damaged patients (e.g., Tompkins, 1990; Giora et al, 2000; Zaidel et al, 2002; Gagnon et al, 2003; Klepousniotou & Baum, 2005; Ianni et al, 2014; Cardillo et al, 2018; Klooster et al, 2020).…”

“…More recently, a growing number of empirical studies have begun to challenge the idea of RH dominance in non-literal processing: brain imaging experiments (e.g., Rapp et al, 2004; Lee & Dapretto, 2006; Bosco et al, 2017; see also Oliveri et al, 2004), meta-analyses of such studies (e.g., Bohrn et al, 2012; Rapp et al, 2012; Reyes-Aguilar et al, 2018), and patient investigations (Ianni et al, 2014; Cardillo et al, 2018; Klooster et al, 2020; see Giora et al, 2000; Zaidel et al, 2002; Klepousniotou & Baum, 2005 for evidence of bilateral involvement) have instead implicated the left hemisphere (LH) .…”

“…Early patient investigations linked difficulties in non-literal interpretation with damage to the right hemisphere (RH) (e.g., Winner & Gardner, 1977; Myers & Linebaugh, 1981; Delis et al, 1983; Brownell et al, 1983; 1986; Bryan, 1988; Joanette et al, 1989; Weylman et al, 1989; Burgess & Charello, 1996; Myers, 1998). More recently, a growing number of empirical studies have begun to challenge the idea of RH dominance in non-literal processing: brain imaging experiments (e.g., Rapp et al, 2004; Lee & Dapretto, 2006; Bosco et al, 2017; see also Oliveri et al, 2004), meta-analyses of such studies (e.g., Bohrn et al, 2012; Rapp et al, 2012; Reyes-Aguilar et al, 2018), and patient investigations (Ianni et al, 2014; Cardillo et al, 2018; Klooster et al, 2020; see Giora et al, 2000; Zaidel et al, 2002; Klepousniotou & Baum, 2005 for evidence of bilateral involvement) have instead implicated the left hemisphere (LH) .…”