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Poster A7, Wednesday, November 8, 10:30 – 11:45 am, Harborview and Loch Raven Ballrooms

Task difficulty affects language production: Behavioral and fMRI evidence

Haoyun Zhang1, Anna Eppes1, Anne Beatty-Martínez1, Christian Navarro-Torres2, Michele Diaz1;1Pennsylvania State University, 2University of California, Riverside

Language production involves a largely left-lateralized network including temporal, frontal, premotor and motor cortices (Indefrey & Levelt, 2000, 2004; Price, 2010). The CRUNCH model (Reuter-Lorenz & Cappell, 2008) has proposed that task difficulty affects the relationship between performance and brain activation, which has not been fully examined in language production. Therefore, this study manipulated task difficulty to explore how difficulty affects language production behaviorally and neurally. 20 individuals (10 females; 18-34 years) participated in a phonological Go-No-Go picture naming task. We manipulated language production difficulty via the proportions of Go trials and No-Go trials across three runs: All Go (named all the pictures), Go Bias (75% Go trials, named pictures whose name started with a consonant, e.g., nose), and No-Go Bias (75% No-Go trials, named pictures whose name started with a vowel, e.g., ear). A lower proportion of Go trials should elicit greater demands in production (Go trials). On the contrary, a higher proportion of Go trials should elicit greater demands in executive function (No-Go trials, inhibition to withhold responses). Behaviorally, participants failed to inhibit responding (No-Go trials) significantly more often in the Go Bias run than the No-Go Bias run (t (19) = 3.73, p = .001), consistent with increased inhibition difficulty during the Go-Bias run. Moreover, participants were slower to name pictures in the No-Go Bias run compared to the other two conditions (ps < .001), suggesting that naming was most difficult in the No-Go Bias run. In the fMRI analysis, we used a linear trend analysis to compare brain activation to Go trials across the three runs to examine effects of naming difficulty (No-Go Bias > Go Bias > All Go). Results revealed that Go trials in the No-Go Bias run elicited greater activation than Go trials in the other runs in right inferior frontal gyrus (pars triangularis, pars opercularis) which extended into posterior superior and middle temporal gyrus and orbitofrontal cortex, and also in left supramarginal and angular gyri. Similarly, we examined inhibition demands across No-Go trials and found that No-Go trials in the Go Bias run elicited greater activation than No-Go trials in the No-Go Bias run in bilateral orbitalfrontal cortex, which extended to superior and inferior frontal gyri, and anterior cingulate cortex. Combined with our behavioral results, these findings confirm that the more difficult conditions (for both naming and inhibition) elicited more extensive activation. Moreover, we found negative correlations between reaction times and brain activation to Go trials across all runs in bilateral precentral and postcentral gyri, extending to superior frontal gyrus, which suggests that greater recruitment of motor regions facilitated naming. Positive correlations were found in left inferior frontal gyrus and fusiform gyrus. Consistent with the CRUNCH model, our results indicate that task difficulty affects language production behavior and fMRI activation and that in younger adults, increased naming difficulty was associated with increased recruitment of inferior frontal regions. Moreover, increased recruitment of bilateral premotor, motor, and superior frontal regions facilitate naming performance.

Topic Area: Control, Selection, and Executive Processes

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