People suffering from tinnitus, a condition of persistent
ringing in the ears, process emotions differently from those with normal
hearing, as per researchers.
Patients afflicted with tinnitus constantly hear noises that are not actually present. These illusory noises are not speech, but rather whooshing noises, train whistles, cricket noises or whines.
The severity of noises differs from one day to another.
The most common cause of tinnitus is noise-induced hearing loss. Increased stress, depression, anxiety, irritability which are linked to brain's emotional processing systems also can cause tinnitus.
"Obviously, when you hear annoying noises constantly that you can't control, it may affect your emotional processing systems," University of Illinois speech and hearing science professor Fatima Husain said. "But when I looked at experimental work done on tinnitus and emotional processing, especially brain imaging work, there hadn't been much research published."
She used functional magnetic resonance imaging (fMRI) brain scans to determine the effects of tinnitus on the brain's emotion processing systems. The scans visualized those areas of the brain that respond to stimulation depending on blood flow to those areas.
The study subjects included three groups of people - those with mild-to-moderate hearing loss and mild tinnitus, those with mild-to-moderate hearing loss without tinnitus and a control group of same-age people with neither hearing loss nor tinnitus.
Each participant was made to listen to a standardized set of 30 emotionally pleasant, 30 unpleasant and 30 neutral sounds (for example, a baby laughing, a woman screaming and a water bottle opening). Then, they were asked to press a button to classify each sound as pleasant, unpleasant or neutral.
The study revealed the tinnitus and normal-hearing people's response to emotion-provoking noises was quicker than their response to neutral sounds. The reacting time of people with hearing loss was similar in all cases.
The overall finding was the people with tinnitus reacted slower than people with normal hearing.
Husain also found to his astonishment that activity in the amygdala (emotional processing part of the brain) was reduced in the tinnitus and hearing-loss group than in the normal-hearing group. But, tinnitus group exhibited increased activity in the parahippocampus and the insula, two other regions of the brain, than normal-hearing people.
"We thought that because people with tinnitus constantly hear a bothersome, unpleasant stimulus, they would have an even higher amount of activity in the amygdala when hearing these sounds, but it was lesser," Husain said. "Because they've had to adjust to the sound, some plasticity in the brain has occurred. They have had to reduce this amygdala activity and reroute it to other parts of the brain because the amygdala cannot be active all the time due to this annoying sound."
Husain called tinnitus a communication and a quality-of-life issue.
She stressed the need to realize how they could get better in the clinical realm and the need to create awareness among audiologists and clinicians in this issue so that they could better serve their patients.
The research was reported in the journal Brain Research.