Sharpening Vision Beyond the Focus Point

Summary: While traditional visual training methods enhance perception only in specific visual regions, a new study presents a breakthrough. By actively exploring visual stimuli via eye movement, participants improved their entire visual field, not just the area they focused on.

This method leverages brain mechanisms linked to eye movements to offer a broader range of perceptual learning. The technique promises more efficient and comprehensive visual rehabilitation programs.

Key Facts:

1. Traditional visual training is limited by location specificity; only enhancing perception in exercised areas.
2. The new study involves active exploration of visual stimuli through eye movement, expanding improved perception to untrained areas.
3. This approach accesses different brain mechanisms, potentially transforming visual rehabilitation efficiency and scope.

Source: LMU

Constant training improves the capacities of human perception. Just as years of practice hone the senses of smell and taste of sommeliers, for example, so experienced radiologists are able to spot anomalies in X-rays at a glance.

Conventional training methods in the medical field of visual perception have been limited, however, as improvements have been obtainable only in the specific area of the field of vision that is being exercised – a phenomenon known as location specificity.

If somebody is recovering from acute vision loss after an accident, for example, their eyesight has to be individually trained for various parts of the visual field during their rehabilitation programs, which is a laborious process. This is so because the visual system processes the world in a spatially ordered manner.

“Neurons that process two neighboring areas in the visual field are also located in close proximity to each other in the brain,” explains Professor Zhuanghua Shi from the Chair of General and Experimental Psychology at LMU.

“Consequently, visual training generally produces plasticity in a small group of neurons that cover a very specific location of the field of vision.”

A new study recently published by a team of researchers led by Shi in the journal Proceedings of the National Academy of Sciences (PNAS) now offers an approach that could remove this limitation.

“We’ve cracked the code for how to expand the advantages of visual training to the entire field of vision,” says Shi’s colleague Professor Heiner Deubel.

In contrast to traditional methods, in which visual stimuli are shown merely at specific locations in the visual field, the study participants actively explored the visual stimuli through movement of their eyes.

This innovative approach induced the participants to use certain mechanisms that are associated with eye movements and flexibly encode the location of the visual stimuli. As a result, their perceptual capacities not only improved in the area they were looking at, but this increased ability also spread to other, untrained sections of their visual field.

The results of the study indicate that the targeted activation of eye movements in perceptual learning accesses completely different brain mechanisms than previous methods.

“This is a very interesting prospect especially for programs of visual rehabilitation, which the new approach can make more effective and less cumbersome,” says Shi.

About this visual neuroscience research news

Author: Constanze Drewlo
Source: LMU
Contact: Constanze Drewlo – LMU
Image: The image is credited to Neuroscience News

Original Research: Closed access.
“Perceptual learning across saccades: Feature but not location specific” by Zhuanghua Shi et al. PNAS

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Abstract

Perceptual learning across saccades: Feature but not location specific

Perceptual learning is the ability to enhance perception through practice. The hallmark of perceptual learning is its specificity for the trained location and stimulus features, such as orientation. For example, training in discriminating a grating’s orientation improves performance only at the trained location but not in other untrained locations.

Perceptual learning has mostly been studied using stimuli presented briefly while observers maintained gaze at one location.

However, in everyday life, stimuli are actively explored through eye movements, which results in successive projections of the same stimulus at different retinal locations.

Here, we studied perceptual learning of orientation discrimination across saccades. Observers were trained to saccade to a peripheral grating and to discriminate its orientation change that occurred during the saccade.

The results showed that training led to transsaccadic perceptual learning (TPL) and performance improvements which did not generalize to an untrained orientation. Remarkably, however, for the trained orientation, we found a complete transfer of TPL to the untrained location in the opposite hemifield suggesting high flexibility of reference frame encoding in TPL.

Three control experiments in which participants were trained without saccades did not show such transfer, confirming that the location transfer was contingent upon eye movements. Moreover, performance at the trained location, but not at the untrained location, was also improved in an untrained fixation task.

Our results suggest that TPL has both, a location-specific component that occurs before the eye movement and a saccade-related component that involves location generalization.