Can Your Hearing Have an Effect on Your Ability to Process Touch?

Those born deaf will process the feeling of touch in a different manner than those born with normal levels of hearing. Findings reveal an early loss in senses can affect an individual’s brain development. It tacks on to the increasing list of new information confirming the impact of any influences from the outside world and experiences that help mold the brain as it develops.
Researcher shows that those born without hearing use their auditory cortex for processing feelings of touch and their visual stimuli far more than those of the hearing population do. Since the developing cortex of those with significant hearing problems is unexposed to any sound stimuli, it ends up adapting and taking on additional tasks for processing information.

Research shows exactly how the brain can rewire itself in the most dramatic of ways. It is of extreme interest to those currently studying the multisensory processing throughout the brain. Previous research shows that those born without hearing are more adept at processing motion and their peripheral vision. Those born with a hearing impairment may end up processing vision in different areas of the brain, especially when it comes to the auditory areas surrounding the primary cortex. No one has been able to tackle whether touch and vision are processed in a different manner when the individual was born without hearing. Due to the experimental settings, it can be extremely hard to produce the type of stimuli needed to find the answer to this question.

Dr. Karns and all of her colleagues developed one of the most unique apparatuses around that enables the user to wear them much like headphones as the patient was put into an MRI scanner. A flexible piece of tubing was connected into a compressor within a separate room, which then delivered small puffs of air directly above the individual’s right eyebrow and below their right eye on the cheek. Brief flashes of light were sent through an optic cable that was mounted beneath the air nozzle. The functional MRI helped measure the reaction of the stimuli at the base of the auditory cortex within the person’s temporal lobe, in addition to other areas of the brain.

Researchers were able to take advantage of the already diagnosed perceptual illusion in those who can hear, which is known as the double flash induced by auditory responses. This allows a singular flash of light along with at least two auditory events to be perceived as if here were multiple light flashes. In the experiment, researchers used the double air puffs as a stimulus for replacing that of the auditory stimulus; however, they kept the one flash of light instead of adding in multiples. The individual’s were also subjected to that of tactile stimuli as well as that of light stimuli on separate occasions and times without the stimuli in an attempt to establish a base for brain activities.

Hearing individuals that were given more than one puff of air and a single flash of light reported only seeing one flash. When the ones without hearing were exposed to identical circumstances, they reported seeing multiple flashes of light. As the scientists looked at the brain activity of those without their hearing, they noticed the activity was far greater within the cortex. However, not all of the brains responded in the same manner or to the same extent. Individuals who are deaf accompanied by the highest degree of activity also had the highest level of response in terms of illusion.

This study proves to be helpful to those without hearing on numerous levels. If vision and touch are interacting more within the deaf population, touch might be useful for the deaf population in learning how to read or compute math problems. It also proves beneficial in helping clinicians improve upon an individual’s hearing quality after getting a cochlear implant, especially among those who received an implant after the age of three. Since these children have been without auditory input since they were born, many will struggle with speech and comprehension due to the way in which their auditory cortex is taking on the other senses. All of these changes can make it more difficult for the cortex to recover the auditory functions after their implants. Knowing how to measure the cortex and how much of it is being ran by the other sensory processors will help provide the necessary input into the types of programs needed for retraining the brain and devoting the necessary capacities to processing auditory signals.