Explaining training induced performance increments and decrements within a unified framework of perceptual learning

Abstract

Practicing sensory tasks could result in two main perceptual outcomes. The first, and more widely documented, is perceptual learning referring to long-lasting improvement of perceptual thresholds. The second is perceptual deterioration, which is observed when the number of trials is increased within a training session or between closely spaced sessions. Recent results with visual texture discrimination show that these two processes inversely affect each other: decremental effects interfere with further learning, while efficient short practice results in a long-term learning effect in which performance decrements are practically eliminated. Further results show that sleep is necessary to preserve learning effects following short training and facilitates the decay of deterioration that normally results from extensive training. We suggest a theoretical link between perceptual deterioration and learning, assuming a system with saturating connectivity. Training strengthens task related connections, with further training leading to saturation of these connections along with strengthening of less efficient connections corresponding to accumulated noise in the network. Such saturation in network connectivity and reduction of signal-to-noise ratio consequently affects the readout of the network, causing deterioration in discrimination performance. Thus, best learning is achieved with short training sessions. Resistance to saturation is achieved by sleep-dependent consolidation of unsaturated connectivity. The different transfer properties of the performance decrements and increments allow us to identify local and global components of perceptual learning and their interactions. This suggests sleep-dependent consolidation mechanisms that induce modifications in higher brain areas that interact with local early visual networks to enable improvement of perceptual abilities.