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Poster E40, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Neural correlates of naming practice of nouns and verbs: An fMRI study in healthy controls

Ekaterina Delikishkina1,3, Angelika Lingnau1,2, Gabriele Miceli1,3;1University of Trento, 2Royal Holloway University of London, 3International Doctorate for Experimental Approaches to Language and Brain (IDEALAB), Universities of Trento, Groningen, Newcastle, Potsdam & Macquarie University

Attempted naming can improve performance in aphasic individuals even in the absence of feedback (Howard et al., 1985; Nickels, 2002). As argued by Heath et al. (2015), neural mechanisms underlying these improvements could at least partially overlap with those that support naming facilitation in the healthy brain. We aimed to investigate neural changes associated with intensive vocabulary practice in healthy individuals. Twenty native Italian speakers (mean age 23.8 years) underwent training of nouns and verbs for ten consecutive days. During each training session they were asked to name twenty objects and twenty actions depicted in color photographs, and were instructed to repeat this procedure ten times. Two identical fMRI sessions were conducted before and after the training period. In the scanner, participants were presented with line drawings of items involved in training, as well as an equal number of untrained objects and actions that served as controls for task habituation effects. For the fMRI analysis we selected 11 left-hemispheric ROIs with a 5-mm radius centered around the coordinates reported in previous studies (Basso et al., 2013; MacDonald et al., 2015). Individual mean beta weights were extracted from each ROI as an estimate of the blood-oxygen level-dependent (BOLD) amplitude and submitted to a repeated-measures ANOVA with factors word class (nouns, verbs) and training (trained, untrained). The ANOVA revealed a main effect of training in the pars triangularis, pars opercularis, anterior insula, anterior cingulate cortex (ACC), mid portion of the middle temporal gyrus (midMTG), posterior cingulate cortex (PCC) and precuneus, as well as a main effect of word class in the pars opercularis, midMTG and posterior inferior temporal gyrus (with verbs eliciting a greater response in comparison to nouns in all three ROIs). The lack of an interaction between the two effects suggests that practice-induced changes were not modulated by word class. Interestingly, changes in the BOLD amplitude in response to training were opposite in their direction in different ROIs — while in the anterior brain regions (including two ROIs within the inferior frontal gyrus, insula and ACC) the BOLD signal was significantly reduced for the trained items, it was increased after practice in the more posterior midMTG, precuneus and PCC. The reduced BOLD response in the frontal regions could be attributed to the facilitation of semantic and/or phonological retrieval and the increased frequency of trained items in the subjects’ mental lexicon. The portion of midMTG selected for the analysis is implicated in semantic storage, and the increase of the BOLD signal for trained in comparison to untrained items may reflect the strengthening of structural representations of objects and actions as a result of practice. Higher BOLD amplitude in response to trained items in the medial parietal regions is more difficult to interpret. While not included in the classic language circuit, PCC and precuneus have been suggested to be an important part of the semantic system (Binder et al., 2009). The exact role of these areas in semantic processing and their functional and structural connections to the language circuit remain to be investigated.

Topic Area: Meaning: Lexical Semantics

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