| Summary: | Williams syndrome (WS) is a rare developmental disorder accompanied by mild–moderate learning difficulties. The literature focusing on older adults with WS is limited, thus the thesis examined cognitive and executive dysfunction in adults with WS aged 35+ years, adopting behavioural and electrophysiological methodologies. Claims of premature cognitive ageing, investigated with paired-associates paradigms to measure associative memory ability (Chapter 2), were not supported, rather they highlighted atypicalities capitalising on semantic memory and implementing spontaneous semantic encoding strategies. Further investigation of semantic memory (Levels of Processing paradigm, Chapter 3) showed better recall for ‘deep’ encoded items; however, effect sizes identified atypical access to semantic memory. Importantly, both studies were characterised with greater false alarms and reaction time for rejecting new items, indicative of poor error monitoring, and deficits in executive processes of inhibitory control and attention in WS. Chapter 4 adopted The Sustained Attention to Response Task which is highly sensitive to inhibition and attentional lapse. The WS group showed inhibitory deficits failing to withhold a response, and problems re-engaging attentional control after making an error. Chapters 5 and 6 investigated the neural mechanisms underpinning attentional / inhibitory deficits, employing the Oddball paradigm (ERP), and analysis of the alpha and beta frequency bands during resting states (EEG). The WS group showed a) compromised early monitoring of perceptual input, and inefficient task irrelevant stimulus evaluation, and b) low EEG alpha power indicative of reduced inhibitory control, atypical topographical distributions, and low variability; the latter is associated with poorer behavioural performance. Overall, the thesis has demonstrated how cognitive deficits observed in older adults with WS are grounded in atypicalities in the executive processes of attention and inhibition. It has added to theoretical understanding by advancing our knowledge of both the behavioural and eletrophysiological profiles in older adults with WS, and which sub-serve these atypicalities.
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