Abstract
This study examined brain activation while participants read or listened to high-imagery sentences like The number eight when rotated 90 degrees looks like a pair of spectacles or low-imagery sentences, and judged them as true or false. The sentence imagery manipulation affected the activation in regions (particularly, the intraparietal sulcus) that activate in other mental imagery tasks, such as mental rotation. Both the auditory and visual presentation experiments indicated activation of the intraparietal sulcus area in the high-imagery condition, suggesting a common neural substrate for language-evoked imagery that is independent of the input modality. In addition to exhibiting greater activation levels during the processing of high-imagery sentences, the left intraparietal sulcus also showed greater functional connectivity in this condition with other cortical regions, particularly language processing regions, regardless of the input modality. The comprehension of abstract, nonimaginal information in low-imagery sentences was accompanied by additional activation in regions in the left superior and middle temporal areas associated with the retrieval and processing of semantic and world knowledge. In addition to exhibiting greater activation levels during the processing of low-imagery sentences, this left temporal region also revealed greater functional connectivity in this condition with other left hemisphere language processing regions and with prefrontal regions, regardless of the input modality. The findings indicate that sentence comprehension can activate additional cortical regions that process information that is not specifically linguistic but varies with the information content of the sentence (such as visual or abstract information). In particular, the left intraparietal sulcus area appears to be centrally involved in processing the visual imagery that a sentence can evoke, while activating in synchrony with some core language processing regions.
Highlights
Many types of thinking, language comprehension, entail the use of mental imagery
Previous studies have indicated that mental imagery generated from verbal instructions and from visual encoding activate similar cortical regions (Mazoyer et al, 2002; Mellet et al, 1996, 1998, 2002)
We measured the functional connectivities of these two areas to five left hemisphere ROIs, including ROIs centrally involved in language processing, and compared them using an ANOVA with two factors: condition and target ROI (LIPS vs. LT)
Summary
Language comprehension, entail the use of mental imagery. Several studies examining mental imagery have observed activation of the parietal area (Dieber et al, 1998; Ishai et al, 2000; Just et al, 2001; Kosslyn et al, 1993, 1996, 1999; Mellet et al, 1996, 2000), the concrete noun task of Mellet et al (1998) failed to observe such activation This lack of parietal involvement specific to the imagery related to the concrete noun task is interesting because this region has been shown to collaborate closely with prefrontal regions in the performance of working memory processes. One of the main goals was to examine the interaction between two somewhat separable neural systems, the mental imagery and language processing systems To accomplish this goal, we used fMRI to measure the activation levels and the functional connectivities of the regions believed to be involved in mental imagery, to determine the relations between the two systems. The participants were familiarized with the task before performing it in the scanner
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