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From speech and print to meaning: an integrated account of word recognition in young and older adults.

Periodic Reporting for period 1 - VIAWORD (From speech and print to meaning: an integrated account of word recognition in young and older adults.)

Reporting period: 2016-06-01 to 2018-05-31

Language is a uniquely human skill that has allowed us to advance our knowledge and culture over millions of years. Humans can access word meaning via written or spoken language. Thus, comparing the neural basis of the written and spoken word recognition system can improve our theoretical understanding of such a fundamental human cognitive process. In addition, language is a skill that we use throughout our lives. Therefore, understanding the aspects of language that are preserved or decline as we age can help us to maintain such an essential cognitive process.

The main goals of the projects were: 1) to identify modality-specific (visual vs. auditory) neurocognitive processes of word recognition using electrophysiology, and 2) to identify age-related changes in word recognition neurocognitive processes by comparing young and older adults.

To achieve goal one, we compared the results of a speeded and a delayed lexical decision task (in an LDT participants are asked to discriminate words from pseudowords) presented to young adults in the written, spoken and audiovisual (written+spoken) modality while electroencephalogram was recorded. In a LDT, participants are asked to discriminate words from pseudowords. To achieve goal two we compared the brain activity of young and older adults while they performed a delayed LDT.

The main results from goal one show that word meaning –as indexed by an electrophysiologic lexicality effect—was accessed earlier in the visual than in the spoken modality, suggesting the rapid availability of written stimuli leads lexical access. In addition, access to word meaning was modulated by the time pressure participants were asked to make a response: the lexicality lasted longer in the speeded than in the delayed LDT. Further, the lexicality effect was observed again at the time participants made a response in the delayed LDT, suggesting re-accessing of the word in semantic memory in order to accurately perform the task.

The results from goal two show that there are brain dynamics’ differences between young and older adults when they recognize words. The main findings include a right-lateralized distribution of the lexicality effect in older adults, suggesting a specialized semantic system in the aging brain, and longer activation of the effect in the visual and audiovisual modalities in older relative to young adults, suggesting that older adults maintain the concept active in memory until the time of responding in order to perform as accurately as young adults.
Study 1a: cross-modality time course of speeded word recognition (21 participants)
Method: visual, auditory and audiovisual lexical decision task and event-related potentials (ERPs)
Results:
1) lexical access starts earlier in the visual than in the auditory modality
2) more negative ERP amplitudes predict slower speed of responding across modalities.
Conclusions:
1) a written stimulus presented all at once provides an advantage over its auditory counterpart when recognizing words both at the behavioral (speed of responding) and neurophysiological level
2) the speeded LDT tapped into both lexical access and response processes. However, in order to properly tease both processes apart we conducted study 1b, explained below.
Dissemination: 2018 International Meeting of the Psychonomic Society, Amsterdam, The Netherlands.
Manuscript in preparation: López Zunini, R.A. Samuel, A. G., Baart, M., & Armstrong, B. C. The temporal dynamics of visual and auditory word recognition: Insights from behavioral and neural measures.

Study 1b: cross-modality time course of delayed word recognition (21 participants)
Methods: visual, auditory and audiovisual lexical decision task and event-related potentials (ERPs)
Results:
1) lexical access starts earlier in the visual than in the auditory modality
2) re-instantiation of the lexicality effect at the time of responding
3) more negative ERP amplitudes at the time of responding predict slower speed of responding across modalities.
Conclusions:
1) replication of result 1 in study 1a
2) the re-instantiation effect suggest there is re-activation of the stimuli in memory and the time of responding
3) the predictive ERP amplitudes were shifted toward the post-response time window, indicating that such amplitudes are related to post-lexical response processes rather than to lexical access itself.
Dissemination: 2018 International Meeting of the Psychonomic Society, Amsterdam, The Netherlands.
Manuscript in preparation: López Zunini, R.A. Samuel, A. G., Baart, M., & Armstrong, B. C. The temporal dynamics of visual and auditory word recognition: Insights from behavioral and neural measures.

Study 2: cross-modality word recognition in young and older adults (20 young adults and 21 older adults)
Method: visual, auditory and audiovisual delayed lexical decision task and event-related potentials (ERPs)
Results:
1) right-lateralization of lexicality effect across modalities in older adults
2) the lexicality effect post-response was larger in older adults when compared to young adults
3) larger lexicality effect in older than young adults in the audiovisual modality.
Conclusions:
1) the right-laterization of the effect in older adults suggest that they process semantic information qualitatively different from young adults. It seems older adults have a more focused lexico-semantic system
2) the larger post-response effect may reflect a compensatory mechanism that may help older adults keep up with young adult-like accuracy at the time of responding
3) older adults benefit more from multisensory information than young adults, perhaps by relying more on internal semantic knowledge rather than the physical characteristics of visual or auditory stimulus.
Dissemination: 2018 10th Annual Meeting of the Society for the Neurobiology of Language, Quebec City, QC, Canada.
Manuscript in preparation: López Zunini, R.A. Samuel, A. G., Baart, M., & Armstrong, B. C. The temporal dynamics of visual and auditory word recognition in the ageing brain: An Event-Related Potential study.
This project provided an improved theoretical understanding of access to word meaning in the written and spoken language, as well as an improved understanding of how ageing affects it. More specifically, we found that written and spoken word recognition differ in the time course of access to meaning, and that lexical and response processes can be modulated by the speed of responding. In terms of ageing, we found that older adults recognize words as efficiently as young adults despite quantitative and qualitative differences in brain activity.
Graphic distribution of lexico-semantic acess in young and older adults