Sensory device may help blind ‘see’

By Lauretta Ihonor

Study results indicate that the use of a sensory substitution device (SSD) may allow individuals with visual impairments to experience a form of spatial awareness conventionally thought to be vision-specific.

The authors say: "Our current study lends support to the hypothesis that the representation of space in the brain is modality-independent, or that very little training is required to create a 'visual'-like representation of space, using sounds, to guide fast and accurate movements."

The SSD device, called EyeMusic, developed by Amir Amedi and team at The Hebrew University in Jerusalem, Israel, uses musical tones and scales to represent the appearance and location of images.

The position of an image is represented by the timing of a musical note played, the brightness is represented by the volume of the note, and different musical instrument sounds represent different image colors.

The team reports that the SSD was tested among 18 sighted individuals with a mean age of 24.5 years.

After a familiarization session, the individuals were blindfolded and asked to make fast reaching movements toward an onscreen target. The movements were made in response to SSD cues.

These SSD-guided responses were then compared with responses made without blindfolding.

The findings, reported in Restorative Neurology and Neuroscience, showed no significant difference in the speed, movement time, and path length of responses to the target when participants were under SSD-guidance compared with visual-guidance.

However, target-position identification was less accurate with SSD-guidance than with visual guidance, although the difference in accuracy was small.

Indeed, SSD-guided responses were a mean of 0.41 cm away from the true location of the target.

This, say Levy-Tzedek and team, indicates that "task-specificity, rather than modality-specificity, of brain functions is crucially important for the rehabilitative use of SSDs in the blind and the visually impaired."

They conclude that the high level of accuracy level reached in this study shows that SSDs may be useful in assisting visually impaired individuals with daily tasks that involve fast and specific reaching movements.

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