Abstract
Previously, Rousselet et al. (Frontiers in Psychology 2010, 1:19) reported a 1ms/year delay in face visual processing speed in a sample of 62 subjects aged ~20-80, using event-related potentials (ERPs). This result was replicated in another 59 subjects, and was independent of stimulus luminance and senile miosis (Bieniek et al. Frontiers in Psychology 2013, 4:268). To go beyond differences in average brain activity and interpret previous findings, here we investigated what information is coded by early face ERPs in younger and older observers. In a detection task, nineteen older (7 female, median age: 66, 60-86) and eighteen younger (9 female, median age: 23, 20-36) observers each categorized 2,000 pictures of faces and noise textures revealed through 10 Gaussian apertures (“bubbles”; Gosselin & Schyns, Vision Research 2001, 41:2261). Using reverse correlation and Mutual Information (MI), we found that the presence of the left eye elicited fastest detection in both age groups, even though older observers relied more on the eyes to be accurate, suggesting a strategy difference. In both age groups, presence of the eye contralateral to the recording electrode modulated most single-trial ERPs at lateral-occipital electrodes, but this association was about 54% weaker in older observers, and delayed by about 40 ms. We also observed a differentiated coding of the eyes across groups: in younger observers, both the N170 latency and amplitude coded the contralateral eye (Rousselet et al. Journal of Vision 2014, 14(13):7, 1–24), whereas it was only the N170 amplitude in older adults. The latency modulation in younger adults was also higher in the right than in the left hemisphere and very similar across hemispheres in older adults. Our results suggest that ageing is associated with both quantitative differences in face processing (general delay, weaker feature sensitivity, decreased hemispheric lateralization), and qualitative differences (nature of information coding).
Meeting abstract presented at VSS 2015