Effects of age-related cognitive deficits on EEG phase coherence

Abstract

Abstract-Body and brain undergo several changes with aging. One of these changes is the loss of neuroplasticity, which leads to the decrease of cognitive abilities. Hence the necessity of stopping or reversing these changes is of utmost importance to contemporary society. In the present work, electroencephalogram (EEG) markers of cognitive decline are sought whilst the subjects perform the Wisconsin Card Sorting Test (WCST). Considering the expected age-related cognitive deficits, WCST was applied to young and elder participants. The results suggest that coherence on theta and alpha EEG rhythms decrease with aging and increase with performance. Additionally, theta phase coherence seems more sensitive to performance, while alpha synchronization appears as a potential ageing marker. I. INTRODUCTIONThe process of healthy aging often involves loss of synaptic contacts and neuronal apoptosis, which can lead to declines in the episodic and working memory functions. Neural redundancy and plasticity, alongside with mental and physical training, promotes maintenance of brain activity avoiding the appearance of neuronal impairments, such as Alzheimer's disease and mild cognitive impairment [1][2]. In several studies, the electroencephalogram (EEG) has been used to determine which neuronal areas, their cognitive function and rhythms, are altered with aging [1]. Working and episodic memory studies have been reporting an increase of theta activity during the encoding phase [3]. Alpha activity has been associated to attention and binding processes [3][4]. Among other measures, these studies often apply coherence analysis to detect inter-regional EEG activation changes, both for stimulus-locked and background activations [5].The Wisconsin Card Sorting Test (WCST) is a common neurophysiologic task used to evaluate complex cognitive functions such as working memory and rule shifting. Although WCST has been used to detect frontal dysfunction, recent studies show that the WCST is sensitive but not specific of the frontal regions malfunctioning [6]. A good performance in the WCST involves other brain regions besides the frontal areas, such as parietal and temporal locations [6].In this study we analyzed the effects of age-related cognitive deficits on EEG phase coherence among frontal and parietal locations. The region pairs with EEG coherence *Research co-sponsored by the Portuguese Foundation for Science and Technology and COMPETE program.

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