Scaling effects in crossmodal improvement of visual perception by motor system stimulus

This work underlines the substantial similarity between deficitary and normal brain neural network, which appear to be related by a change of scale of their cerebral excitabilities. Extending the previous works on multisensory effects and crossmodal facilitation in subjects with cortical lesions, we observe similar phenomena, but much weaker, in normal subjects. Specifically, visual acuity is observed to slightly improve in 10 normal subjects under moderate, static muscular effort, and a scaling power law is found to characterize the improvement with the intensity of the effort. This fact supports the generality of the idea of distributed functionality of motor cortex and sensory systems through the whole cortex. The mechanism of activation of unspecific (or multispecific) neural mass that explains facilitation phenomena in damaged brain appears here to be similar in normal brain. The scaling power law for the improvement of perception with intensity of facilitating stimulus would reflect basic biological scaling power laws with the activated mass of the neural network.