How senses combine to help us better perceive our environment

Washington, Nov 13 : In a new study, scientists have delved into one of the biggest questions plaguing brain research- how different human senses combine to give us a better view of the world.

Recent studies have claimed that there is actually a lot of overlap and blending of the senses occurring in the brain to help us better perceive our environment.

The study by researchers J.E. Lugo and colleagues at the University of Montreal, along with Walter Wittich from McGill University, was aimed at finding how different senses work simultaneously.

They wanted to know if a feeling from an electrical stimulation of a body part (such as the leg) which normally would not be perceived, would be felt if it was simultaneously accompanied by a visual or auditory signal.

For the study, the researchers applied slight electrical stimulation to the right calf of volunteers-the stimulation was so slight that the participants did not detect it.

Then, they paired that electrical stimulation simultaneously with a visual signal, a distinct noise or a progressively louder white noise signal. The volunteers reported when they felt anything in their leg and the electrical response of the calf muscle activation was measured.

It was found that if an electrical stimulation of the leg is not initially detected, the sensation may be perceived by the addition of a visual or auditory signal with a corresponding electrical activation increase.

The scientists observed that the brain not only constantly processes information received from the senses, but also acts on that information to change what is happening in the peripheral system, and thus changing what we actually detect.

The results of the last experiment are characteristic of stochastic resonance, which is an interesting phenomenon where as noise is added to a system, the system's performance improves until, at a certain point, the performance begins to deteriorate.

That's what was found in the study-as the researchers increased the signal, participants reported more feeling in their leg, which eventually decreased, even as the signal continued to get louder.

The scientists observed the resonance signature even if the stimulus they used in the experiment was not noise but a pulse.

The results indicate that a tactile stimulus combined with a specific level of auditory stimulation results in optimal detection of that sensation. However, too much signal energy will limit the response. It also shows that these dynamics represent a fundamental principle of multisensory integration.

The study provides insight into multisensory integration, which according to the authors, will result in increased knowledge of how the brain normally interacts with the peripheral system.

Also, learning more about multisensory integration may pave the way for a better understanding of disorders such as autism, in which altered sensory processing often occurs.

The study was reported in Psychological Science, a journal of the Association for Psychological Science.

ANI