Event Abstract

Differential impact of listener age on early versus late components of magnetic MMN response to spoken words.

  • 1 MRC Cognition & Brain Sciences Unit, United Kingdom

We assessed applicability of a mismatch paradigm in demonstrating age-related changes in the dynamics of linguistic brain activity. Two subject groups consisted of 15 older (mean age 67.2 years) and 18 younger (24.6 years) English speakers. Four standard stimuli, occurring in separate blocks, were two English word stems (“play”, “tray”), one acoustically similar pseudoword (“qway”) and one acoustically matched non-speech stimulus. Two deviants in each block differed from the standards by addition of a /d/ or /t/ ending (10% each) making them different words (e.g. “play” vs. “played” and “plate”). Standard stimuli were matched for total length (310ms), vowel duration and mean power. Closure time between stem offset and onset of the /d/ or /t/ ending was 10ms and 80ms, respectively, in accordance with natural English phonology. Auditory MEG responses elicited by these stimuli were recorded in a passive non-attend oddball paradigm while participants watched a silent film.

We found that:
1) All mismatch responses, across both age groups, were characterized by greater magnitude in the left hemisphere, reflecting the word/word-like nature of the stimuli.
2) Deviants ending in /t/ relative to /d/ resulted in consistently greater magnitude of MMNm response, explicable in terms of the acoustic differences between these stimulus types: reduced closure time for /d/ results in stronger masking effects from preceding stems. This is relevant to patterns of past-tense verb deficits in some aphasic patients.
3) The early (~50ms) phase of responses was markedly larger in older than younger participants. This early enhanced response to phonological stimulation may reflect reduced neural adaptation to repetitive auditory events. Alternatively, it may indicate recruitment of additional neural resources necessary for stimulus perception by the ageing brain.
4) Conversely, the main peak of the MMNm responses (~100-125ms) was markedly smaller in older than younger individuals. As linguistic MMNs have been linked to long-term memory traces for language elements in the brain, this reduction of MMNm in older participants may be a sign of instability of such memory traces with ageing. Alternative or additional factors include modification of responses due to brain volume changes and greater variability in the older group.
5) A trend for enhancement of later (>130ms) MMNm response dynamics for words relative to pseudowords was evident only in the younger participants. This replicates previous findings of lexical MMN enhancement linked to word memory representations and suggests that this enhancement may be eroded by ageing.

Conference: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009.

Presentation Type: Poster Presentation

Topic: Poster Presentations

Citation: Brindley L, Holland R, Tavabi K, Pulvermüller F, Patterson K and Shtyrov Y (2009). Differential impact of listener age on early versus late components of magnetic MMN response to spoken words.. Front. Hum. Neurosci. Conference Abstract: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications. doi: 10.3389/conf.neuro.09.2009.05.134

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Received: 26 Mar 2009; Published Online: 26 Mar 2009.

* Correspondence: Lisa Brindley, MRC Cognition & Brain Sciences Unit, Cambridge, United Kingdom, lisa.brindley@mrc-cbu.cam.ac.uk

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