Presentation
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Neural correlates of linguistic and non-linguistic demand in the visual and auditory modalities
Poster E103 in Poster Session E, Thursday, October 26, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Stephen M. Wilson1,2, Mackenzie Philips2, Ian A. Quillen2, Sarah M. Schneck2, Deborah F. Levy2, Melodie Yen2; 1University of Queensland, 2Vanderbilt University Medical Center
A major challenge in interpreting functional imaging studies of language processing in clinical populations is the difficulty of matching processing effort across groups (e.g., individuals with aphasia compared to controls) and across tasks (e.g., linguistic versus non-linguistic) [1,2]. Processing effort strongly modulates neural activity in many brain regions, but how specific brain regions respond to different kinds of effort in different contexts remains poorly understood. To address this gap, we investigated the neural correlates of task difficulty as a function of task domain (linguistic, non-linguistic) and stimulus modality (visual, auditory) [3,4]. Thirty-nine neurologically normal individuals were scanned with fMRI (age 28–40 years; 34/5 female/male; all left-lateralized for language). Stimulus modality was a between-subjects variable: 20 participants performed tasks in the visual modality and 19 in the auditory modality. In a block design, participants performed easy and difficult linguistic tasks (deciding if two words were semantically related) and easy and difficult non-linguistic tasks: identifying matches between pairs of symbol strings (visual), or pairs of melodies (auditory). Behavioral data showed that our manipulations of difficulty yielded expected effects on accuracy and reaction time, which were generally well matched across domains and modalities. The functional imaging data were analyzed using standard methods. Whole brain analyses were subject to a cluster-defining threshold of p<.005 and corrected for multiple comparisons at p<.05 based on permutation analysis of cluster extent. We also carried out a parallel analysis using functionally defined regions of interest in individual participants [5]. We found that linguistic demand modulated left hemisphere language regions—the IFG and the STS—as well as the right IFG to a lesser extent, in both the visual and auditory modalities. Linguistic demand also modulated the “multiple demand” (MD) network, but surprisingly, only in the visual modality, not in the auditory modality. Non-linguistic demand did not modulate language regions in either modality. The regions modulated by non-linguistic demand were strikingly different in the two modalities investigated: in the visual modality, non-linguistic demand strongly modulated the MD network, while in the auditory modality, only the right anterior insula was modulated. Our findings have implications for the interpretation of clinical studies. The language network is modulated by linguistic demand irrespective of modality, implying that between-groups differences in language regions should be interpreted carefully, because they may reflect differences in linguistic demand. In contrast, it appears that the MD network is not obligatorily recruited for effortful language processing, since its modulation was modality-dependent in our data, and other studies have suggested that this network is minimally involved in natural language processing [6,7]. Activation of the MD network apparently depends on task details that are not well understood, so differences between clinical groups within the MD network should be approached with caution [1,2]. References: [1] Geranmayeh et al. Brain 2014;137:2632–2648; [2] Wilson & Schneck. Neurobiol Lang 2021;2:22–82. [3] Quillen et al. Neurobiol Lang 2021;2:202–225. [4] Philips et al. Neurobiol Lang 2023; in press. [5] Fedorenko et al. J Neurophysiol 2010;104:1177–1194. [6] Wehbe et al. Cerebral Cortex 2021;31:4006–4023. [7] Shain et al. J Neurosci 2022;42:7412–7430.
Topic Areas: Control, Selection, and Executive Processes, Disorders: Acquired