Age Related Changes in Motion Perception and Perceptual Learning
- Author(s): Bower, Jeffrey Dennis
- Advisor(s): Andersen, George J
- et al.
The following studies examined age-related decrements in motion perception processing. Using a perceptual learning paradigm, perceptual inefficiency was compared between younger and older observers. Perceptual inefficiency was modeled using the Perceptual Template Model (Lu & Dosher, 1998; Lu & Dosher, 1999). Baseline differences and changes over training were assessed for additive internal noise, tolerance to external noise, and internal multiplicative noise in both older and younger observers. Experiments 1 and 2 examined age-related changes in baseline perceptual inefficiency and learning after training. Experiments 1 and 2 trained participants by manipulating contrast in noise embedded sine-wave gratings and Random Dot Cinematograms (RDCs). The results indicate that older observers have higher additive internal noise and lower tolerance to external noise compared to younger observers. Perceptual learning in older observers was found to be at a similar rate to that of younger observers suggesting that cortical plasticity for motion processing is well preserved in advancing age. Experiment 3 examined transfer of learning between sine-wave gratings and RDCs for both older and younger observers. The results indicated that transfer of learning occurred for both age groups. This suggests that older individuals maintain a sufficient degree of plasticity to allow generalization between sine-wave gratings and RDCs. In addition, training with RDCs was found to produce greater perceptual learning than training with sine-wave gratings. Experiment 4 examined if center-surround antagonism could be increased through perceptual training which would provide evidence that neural inhibition is related to internal noise. Center-surround antagonism enables edge detection through an antagonistic interaction between the center and the surround regions of a receptive field. Younger and older participants were trained on duration thresholds with Gabor patches that varied in size and contrast. The results of Experiment 4 indicate that some perceptual learning occurred in both younger and older participants but were inconclusive with regards to inhibition in visual cortex. The present studies provided important findings regarding changes in perceptual efficiency for motion perception in older adults. Cortical plasticity was found to be well preserved in older adults indicating that perceptual training may be an effective way to improve motion perception.