Cognitive Neuroscience Talks

Age-related delay in information accrual for faces: Evidence from a parametric, single-trial EEG approach

We investigated age-related changes in visual processing speed in a face discrimination task using ERPs. Younger (n=13, mean age=22) and older (n=18, mean age=70) observers performed a spatial, two alternative forced choice task between 2 faces. Emphasis was on accuracy, not speed. Stimulus phase was manipulated in a parametric design, ranging from 0% (noise), to 100% (original stimulus). Behavioural 75% correct thresholds were on average lower, and maximum accuracy was higher, in younger than older observers. The earliest age-related ERP differences occurred in the time window of the N170: Older observers had a significantly stronger N170 in response to noise, but this age difference decreased with increasing phase information. These effects were not due to changes in brain signal variance. Overall, manipulating phase had a greater effect on ERPs from younger observers. This result was confirmed by a hierarchical modelling approach. ERPs from each subject were entered into a single-trial multiple linear regression model to identify variations in neural activity statistically associated with changes in image structure (Rousselet, Pernet, Bennett & Sekuler, BMC Neuroscience, 2008). The main model parameters were stimulus phase noise, kurtosis, and a measure of local phase coherence. The fit of the model, indexed by R2, was computed at multiple post-stimulus time points: peak R2 was similar in the two groups, but it occurred at a longer latency in older observers. Overall, our results suggest that older subjects accumulate face information more slowly than younger subjects. Despite the overall age-related group differences, within each age group chronological age did not predict any of the results.