Learning a New Sense

 

Rats use a sense that humans don’t: whisking. They move their facial whiskers back and forth about eight times a second to locate objects in their environment. At the Weizmann Institute, researchers had blindfolded volunteers learn to sense using artificial “whiskers.”  The findings, which appeared in the Journal of Neuroscience, have yielded new insight into the process of sensing, and they may point to new avenues in developing aids for the blind.

The scientific team, including Drs. Avraham Saig and Goren Gordon, and Eldad Assa in the group of Prof. Ehud Ahissar and Dr. Amos Arieli, all of the Neurobiology Department, attached a “whisker” – a 30-cm-long elastic “hair” with position and force sensors on its base – to the index finger of each hand of a blindfolded subject. Then two poles were placed at arm’s distance on either side and slightly to the front of the seated subject, with one a bit farther back than the other. Using just their whiskers, the subjects were challenged to figure out which pole was the back one. As the experiment continued, the displacement between front and back poles was gradually reduced.

Already on the first day of the experiment, subjects picked up the new sense so well that they could correctly identify a pole that was set back by only 8 cm, determining which pole was farther back because the whisker on that hand made contact earlier. In other words, the subjects figured the spatial information from the sensory timing.

When they repeated the testing the next day, the researchers discovered that the subjects had improved their whisking skills significantly: The average sensory threshold went down to just 3 cm, with some being able to sense a displacement of just 1 cm. Interestingly, the ability of the subjects to sense time differences had not changed over the two days. Rather, they had improved in the motor aspects of their whisking strategies: Slowing down their hand motions – in effect lengthening the delay time – enabled them to sense a smaller spatial difference.

Saig: “We know that our senses are linked to muscles: In order to sense the texture of cloth, for example, we move our fingers across it. In this research, we see that changing our physical movements alone can be sufficient to sharpen our perception.”

Ahissar: “Our findings reveal some new principles of active sensing and show us that activating a new artificial sense in a ‘natural’ way can be very efficient.”  Arieli adds: “Our vision for the future is to help blind people ‘see’ with their fingers. Small devices that translate video to mechanical stimulation, based on principles of active sensing that are common to vision and touch, could provide an intuitive, easily used sensory aid.”