Evaluating the contributions of age-related changes in sensory acuity and cognitive control on the speed and accuracy of visual search.

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he ability to identify and locate task-relevant objects in the scene is a key component of functional vision. In psychology and human neuroscience, this ability has been investigated using visual search tasks, which measure the speed and accuracy of detection for a target among a variable number of non-target (distractor) stimuli. Ageing is associated with changes in sensory and cognitive processes, which are likely to impact the efficiency of search. Despite this, empirical evidence to support age-related changes in the efficiency of visual search is mixed. Contradictory findings reflect heterogenous samples and different measures used to investigate age-related changes in sensory and cognitive components. Indeed, studies investigating age-related changes in sensory acuity rarely test cognitive mechanisms associated with the evaluation of competing visual input, short-term memory or the planning and execution of saccades. Experiments also rarely titrate the stimuli presented to old and young participants so to eliminate differences in performance that may have been caused by sensory degradation in the former. For these reasons, the present project will attempt to quantify age-related changes in sensory acuity by employing different psychophysical techniques to measure contrast, spatial frequency, and chromatic sensitivity for stimuli across the visual field. Additionally, since the objective is to measure both the contributions of age-related reductions in perceptual processes and the top-down modulation of cognitive processes that influence visual sampling and the maintenance and evaluation of sensory information, the present project aims to combine simultaneous eye tracking and electroencephalogram (EEG) to obtain accurate measures of the neural responses that modulate target representation, guidance, selection and identification during search. Lastly, this project will attempt to integrate pupillometric recordings of task-related changes in pupil size and EEG power spectrum to contrast cognitive effort and sustained attention in young an older observers in response to changes in the perceptual discriminability of displays, task instructions and prior experience