Spatial interactions in human vision: from near to far via experience-dependent cascades of connections.

Perceptual learning has been shown to affect early visual processes. Here, we show that learning induces an increase in the spatial range of lateral interactions. Using a lateral masking/facilitation paradigm and bandpass-localized stimuli, we measured the interaction range before and after extensive training on a threshold detection task. For naive observers, target threshold was found to be facilitated by mask presence at distances up to six times the target period. However, practice had the effect of increasing the facilitation range by at least a factor of three. We suggest that the induced longer-range facilitation is a result of internal response transmission via a cascade of local connections. The data presented also show that this chain can be broken. These results suggest a plasticity in early vision governed by Hebbian-like rules.