Visual feedback enhances activation of muscle movement in response to bodily sensation

Visual feedback is just as important as a sense of body position when it comes to the involuntary reflexes that activate muscle movement, says a new study in the open-access journal eLife.

The findings provide insights into how the brain balances different types of sensory information to control the earliest stages of movement, adding to our understanding of how these processes are controlled in health and disease.

Throughout daily life, we alter our body movements in response to changing cues.

A key component of this feedback is the 'stretch reflex' of muscle, which occurs milliseconds before the actual voluntary muscle movement.

"Several studies have suggested that the brain integrates multiple types of sensory information to achieve voluntary muscle control," explains lead author Sho Ito, a researcher at NTT Communication Sciences Laboratories, Kanagawa, Japan.

In this study we examined how altering visual cues, such as distorting or eliminating this information, affected the intensity of muscle stretch reflexes."

The team conducted experiments with people who were asked to move a cursor towards a visual target.

They found that the decrease in intensity of the muscle stretch reflex occurred only when distortion was introduced in the visual feedback, but not by a distorted map between visual target and motor action.

"Our study suggests that in the absence of clear visual cues, participants feel unsure of their own hand position, which reduces muscle stretch reflex and prevents an inaccurate or inappropriate movement," concludes senior author Hiroaki Gomi, Senior Distinguished Researcher and Group Leader at NTT Communication Sciences Laboratories.