'Distraction during working memory encoding and maintenance and age-related changes in working memory'

Frankland 309b
Life and Environmental Sciences, Research
Tuesday 13th October 2015 (13:00-14:00)
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Part of the Social Cognitive Neuroscience and Development Group Seminar Series

Speaker: Fiona McNab

The effectiveness of distractor-exclusion is a potentially important determinant of working memory capacity (WMC) (1,2). Until recently it was assumed that the same mechanism underlies distractor-exclusion during WM encoding and during maintenance. With two experiments involving young adults, 1 conducted in the laboratory with 21 participants, and the other played as a game on smartphones (n = 3,247), distractors were presented either during encoding or during the WM delay period, to determine performance associated with these two types of distraction (3). Despite differences in experimental setting and paradigm design between the 2 studies, both show a unique contribution to WMC from encoding and delay distractor performance, while controlling for performance in the absence of distraction. This dissociation between encoding and delay distractor-exclusion, indicates separate mechanisms that contribute to WMC.

A weakened ability to effectively resist distraction is a potential basis for reduced working memory capacity (WMC) associated with healthy aging (4). Again exploiting data from the smartphone game (n = 29,631), it was observed that as age increases, working memory (WM) performance is compromised more by distractors presented during WM maintenance than distractors presented during encoding (5). However, with increasing age, the ability to exclude distraction at encoding is a better predictor of WMC in the absence of distraction. A significantly greater contribution of distractor filtering at encoding represents a potential compensation for reduced WMC in older age.

Both studies (3,5) highlight a dissociation between distractor-exclusion at encoding and delay. The study of aging (5) also indicates that the way in which information is held in WM changes as we age, with a greater involvement of encoding distractor-exclusion, even when no overt distraction is present. Very preliminary data from adolescents will also be discussed.

(1) Vogel, E.K. & Machizawa, M.G. (2004) Neural activity predicts individual differences in visual working memory capacity. Nature, 428 (6984): 748–751.

(2) McNab, F. & Klingberg, T. (2008) Prefrontal cortex and basal ganglia control access to working memory. Nature Neuroscience, 11 (1): 103-107.

(3) McNab, F. & Dolan, R.J. (2014) Dissociating distractor-filtering at encoding and during maintenance. Journal of Experimental Psychology, Human Perception and Performance, 40: 960-7.

(4) Gazzaley, A., Cooney, J.W., Rissman, J. & D’Esposito, M. (2005) Top-down suppression deficit underlies working memory impairment in normal aging. Nat Neurosci 8(10): 1298–1300.

(5) McNab, F., Zeidman, P., Rutledge, R.B., Smittenaar, P., Brown, H.R., Adams, R.A. & Dolan, R.J. (2015) Age-related changes in working memory and the ability to ignore distraction. Proceedings of the National Academy of Sciences, 112 (20): 6515-6518.