engleski

Age related changes in neural dynamics of word processing

Word processing involves a sequence of operations ranging from perceptual/orthographic, such as visual encoding of letters, phonologica l encoding, and activation of lexical and semantic networks to access word meaning. Several event - related (ERP) components associated with word processing have been reported in the literature. P200 component is usually elicited between 100 and 250 ms post - stimulus at fronto - central electrodes and is enlarged when attention is paid to visual stimuli. N200 is typically evoked from 150 to 350 ms in centro - parietal region reflecting classification of relevant stimulus dimensions. The process of understanding a word peaks at about 400 ms after word onset (known as N400) and results from interactive contributions of different brain areas. For this study, we designed a categorization task to elicit perceptual („is the word written in upper - or lowercase letters“) a nd semantic („does the word refer to a living or nonliving object“) components of visual word processing. We compared ERP components in late adolescents aged 19 – 21 years, young adults aged 23 – 27 years and mid adults aged 28 – 44 years (N = 120). Since the way that information is processed can influence memory, immediately after performing the task participants unexpectedly had to orally recall as many words they had encountered in the task as possible. There were no age differences in reaction time bu t mid adults outperformed late adolescents in accuracy. ERP analysis showed age differences in P200 stimulus identification component. The neurophysiological and fMRI data show activation of the left inferior frontal gyrus in first 200 ms of reading and su ggest very early interactions between the vision and language domains during visual word recognition. Inferior frontal gyrus is one of the last brain regions to mature. We speculate that observed age differences in P200 component reflect maturational chang es in the region of cortex giving rise to the P200. Age - related differences were observed on recall task and measure of receptive vocabulary, where mid adults demonstrated greater word knowledge, while late adolescents demonstrated better recall. It seems that late adolescents invested more cognitive effort to identify each word during categorization task, possible reflected in enlarged P200 component. Enhanced effort would leave richer and more elaborate memory trace, and result in better recall.

visual word recognition ; event - related potentials ; incidental recall ; age differences ; young adulthood

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