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Abstract
We used a single-trial ERP approach to quantify age-related changes in the time-course of noise sensitivity. A total of 62 healthy adults, aged between 19 and 98, performed a non-speeded discrimination task between two faces. Stimulus information was controlled by parametrically manipulating the phase spectrum of these faces. Behavioral 75% correct thresholds increased with age. This result may be explained by lower signal-to-noise ratios in older brains. ERP from each subject were entered into a single-trial general linear regression model to identify variations in neural activity statistically associated with changes in image structure. The fit of the model, indexed by R2, was computed at multiple post-stimulus time points. The time-course of the R2 function showed significantly delayed noise sensitivity in older observers. This age effect is reliable, as demonstrated by test–retest in 24 subjects, and started about 120 ms after stimulus onset. Our analyses suggest also a qualitative change from a young to an older pattern of brain activity at around 47 ± 4 years old.
Highlights
Visual cognition depends on fast and progressive transformations of retinal inputs into higher-order representations useful for decision-making (Rousselet et al, 2004; DiCarlo and Cox, 2007; Schyns et al, 2009)
A theory of visual aging must specify how aging affects the time-course of visual processing, the information content of brain activity, and the operations performed on this information
Older subjects needed more stimulus information to achieve the same level of performance as younger subjects, a result that might be explained by lower signal sensitivity in older brains
Summary
Visual cognition depends on fast and progressive transformations of retinal inputs into higher-order representations useful for decision-making (Rousselet et al, 2004; DiCarlo and Cox, 2007; Schyns et al, 2009). The response selectivity of V1 and V2 neurons degrades with age in monkeys (Leventhal et al, 2003; Wang et al, 2005; Yu et al, 2006). In the higher-order cortex of humans, age seems to lessen BOLD preferential categorical responses (Park et al, 2004; Voss et al, 2008). Such changes in tuning may lead to longer processing times, following a model of perceptual decision by accumulation of evidence in neuronal populations (Perrett et al, 1998). EEG and MEG studies in humans have described age-related increases in the peak latency of the P100 component in response to checkerboards and sine-wave gratings (Tobimatsu, 1995)
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