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Poster D20, Thursday, November 9, 6:15 – 7:30 pm, Harborview and Loch Raven Ballrooms

Frontal Shift of the Imageability Effect on N400 in Elders

Chih-Ting Chang1, Chia-Ju Chou1, Jie-Li Tsai2, Chia-Ying Lee1,2,3,4;1Institute of Neuroscience, National Yang-Ming University, Taipei, Taiwan, 2Department of Psychology, National Chengchi University, Taiwan, 3Institute of Linguistics, Academia Sinica, Taipei, Taiwan, 4Institute of Cognitive Neuroscience, National Central University, Taipei, Taiwan

Aging has been associated with cognitive decline and the aging brain may recruit extra brain regions to cope with the declined neural efficiency and cognitive ability. A well-known phenomenon in the cognitive neuroscience of aging, the Posterior-Anterior Shift in Aging (PASA), is that elders tend to exhibit increased prefrontal lobe activation and decreased activation in visual cortex for tasks involving working memory (WM), visual attention (VA), and episodic retrieval. This phenomenon suggests that older adults compensated for visual processing deficits (occipital decrease) by recruiting higher-order cognitive processes (PFC increase). However, it remains unclear whether the PASA phenomena also exist for visual word recognition. Evidences from event-related potentials (ERPs) studies have suggested that high imagery words may associate with richer semantic features and tend to elicited greater N400 than the low imagery words in the frontal sites. Functional neuroimaging studies of imageability have also showed that the semantic retrieval of words with high versus low imageability might involve different weighting in frontal and temporal regions. This study aims to address this question by examining how aging shapes the familiarity and imageability effect on N400. The imageability (high versus low) and familiarity (high versus low) of the target words were manipulated in a two-by-two factorial design. Two groups of participants were recruited, one group includes 19 younger adults (five males; mean age 25.32 years, range 21-36), and the other group includes 18 elder adults (five males; mean age 65.06 years, range 56-78). Participants were requested to carry out a button-press if the target word refers to an animal. Results from both groups showed the typical familiarity effect on N400, in which the unfamiliar words elicited a greater N400 than the highly familiar words. The imageability effect that the high imagery words elicited a significantly greater N400 than the low imagery words only observed in highly familiar condition. The absence of the imageability effect for unfamiliar words may due to the resources occupation between reading and imagery process (Unnava, Agarwal, & Haugtvedt, 1996). For those highly familiar words, the younger group showed the imageability effect in the centroposterior regions, while the elder group showed the effect distributed in the fronto-central region. Our findings consistent with the PASA phenomenon and suggest the age-related compensatory mechanism in visual word processing in elders.

Topic Area: Language Development

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