Neural plasticity underlying visual perceptual learning in aging

Abstract

Healthy aging is associated with a decline in basic perceptual abilities, as well as higher-level cognitive functions such as working memory. In a recent perceptual training study using moving sweeps of Gabor stimuli, Berry et al. (2010) observed that older adults significantly improved discrimination abilities on the most challenging perceptual tasks that presented paired sweeps at rapid rates of 5 and 10 Hz. Berry et al. further showed that this perceptual training engendered transfer-of-benefit to an untrained working memory task. Here, we investigated the neural underpinnings of the improvements in these perceptual tasks, as assessed by event-related potential (ERP) recordings. Early visual ERP components time-locked to stimulus onset were compared pre- and post-training, as well as relative to a no-contact control group. The visual N1 and N2 components were significantly enhanced after training, and the N1 change correlated with improvements in perceptual discrimination on the task. Further, the change observed for the N1 and N2 was associated with the rapidity of the perceptual challenge; the visual N1 (120-150 ms) was enhanced post-training for 10 Hz sweep pairs, while the N2 (240-280 ms) was enhanced for the 5 Hz sweep pairs. We speculate that these observed post-training neural enhancements reflect improvements by older adults in the allocation of attention that is required to accurately dissociate perceptually overlapping stimuli when presented in rapid sequence. This article is part of a Special Issue entitled SI: Memory Å.

Keywords: Aging; Cognitive training; ERP; Perceptual learning; Transfer of benefit; Visual perception; Working memory.

Figure 1. Behavioral Performance

A. An example of the double sweep stimulus; the first sweep shown (left) is expanding and the second sweep (right) is contracting. B. (T2-T1) change in proportion correct accuracies on single sweep stimuli (ss50, ss100 and ss200) for the training group (green) and control group (red). No significant performance differences were observed between groups. C. (T2-T1) change in proportion correct accuracies on double sweep stimuli (ds50, ds100 and ds200) for the training (green) and control (red) group. The training group showed significantly greater accuracies at T2 relative to T1 for the ds50 and ds100 stimuli, compared to the control group.

Figure 2. ERP Responses

A. Top: T1 (red) versus T2 (blue) ERPs time-locked to the stimulus onset of ds50 (left) and ds100 (right) at occipital Oz and central Cz sites. Training group and control group ERPs are on top and bottom, respectively. Negative potentials are plotted above the horizontal and the scale for all ERP time series are depicted in the right bottom-most plot. B. Topography maps for the ds50 N1 ERP peak amplitude in the training group showing enhancement at T2 relative to the T1 session (top row). Topography maps for the ds100 N2 peak amplitude in the training group showing enhancement at T2 relative to T1 (bottom row).

Figure 3. Neurobehavioral Correlations

A. Significant correlation between the ds50 N1 ERP amplitude enhancement from T1 to T2 and performance measures: the ds50 accuracy improvement (A) and the working memory (WM) accuracy improvement (B).