An essential component of object perception involves the detection and discrimination of contours. Studies have shown that contour perception depends significantly on several stimulus factors, such as the alignment of contour elements, and that the effects of these stimulus variables change with healthy aging. However, the neural mechanisms that underlie age differences are not well understood. The present study explores the impact of aging and contour element alignment on contour discrimination by comparing behavioural and neurophysiological measures in younger and older adults.
Electroencephalography (EEG) activity in both age groups was examined during a contour perception task. Participants were presented with a visual stimulus consisting of a spiral-shaped contour embedded among distracters. The contour consisted of multiple, oriented elements, and the alignment of these elements was manipulated between trials to vary contour salience. Contour discrimination ability was assessed by requiring subjects to locate the tail of a spiral contour on each trial. The behavioural data collected to date are consistent with previous findings and show that i) contour discrimination was affected by element alignment; and ii) was generally worse in older adults. Preliminary EEG analyses have also revealed age differences in both the timing and topography of the neural signals evoked by the contour stimulus. Further analyses will examine whether these differences in brain activity correlate to the differences observed in performance. Overall, results suggest that the neural processes underlying contour integration change with age, which may impact our perception of the world around us.