“The brain is much more changeable in circumstances where we thought it could not change.”Īnd that suggests a possible end-run on rehabilitation, he says. We find hearing function is improved” because the auditory cortex has been altered by changes in the visual realm.įinding so much plasticity in “adult” mice (defined as older than the critical period) was “a big surprise,” he says. “When they read Braille, the visual cortex is active. In blind people, visual areas of the brain begin to serve other functions, Kanold says. “Our work has brought some hope that a fixed duration of visual training can improve auditory performance.” In the past, he says, people have been deterred by the need for a long period of darkness, “but this is not that long, you might need a blindfold for x number of hours not weeks or months.” Not blind to the consequencesĪlthough we began with the extraordinary auditory abilities of blind musicians, the present study shows a related but different phenomenon. If seven days of darkness can improve hearing in the mice, Isaiah wonders about people. “What actually happens to the auditory cortex when you visually deprive an animal?” “There was some data to suggest the brain’s ability to change with training, but there was never a fixed paradigm, such as blindfolding, that would lead to so much increase in auditory acuity.” “I don’t think there is a system in place to do this,” says co-author Amal Isaiah, a senior resident in ear, nose and throat medicine at the University of Maryland.
Could a technique based on temporarily restricting vision help people who have difficulty understanding speech in a noisy restaurant, locating the source of a sound or enjoying music? “It’s possible if we keep them in the dark longer, that could make the auditory change more permanent.” Help on the way?įinding flexibility in the brain of a mature mouse just by turning off the lights for a week is significant. In any case, when the lights are turned on after a week, the auditory response returns to its original status, Kanold says. When vision is turned off, neurons in the visual cortex are starved for input, “so they decide to up-regulate the input of auditory information” and/orĪn animal living in the dark pays more attention to auditory stimuli, “and we know that when you pay more attention, you improve your sensory performance.” “Neurons in the normal mice can’t discriminate that, but the dark-raised mice can distinguish it and they are also more sensitive to soft stimuli,” says Kanold. Specifically, the experimental mice became able to distinguish among different pitches, between pure tones of 8,000 hertz and 8,050 hertz. As the synapses between the thalamus and cortex change, “the flow of information into the auditory cortex is increased,” Kanold says. “We know the blind hear much better, but what are the nuts and bolts? What changes?” Electrical selectivityīy recording electrical activity in the brains of mice, the researchers monitored connections, called synapses, between the thalamus and the cortex - an essential transition point for auditory impulses moving from the ears deep into the brain, where they are interpreted as sound. Understanding the impact of blindness was one goal of the study, he points out. Neuroscientists use “plasticity” to refer to changes in the brain as a result of training or experience. Modified from original Thalamus illustration from Shutterstock.
We sat down together and thought, ‘What actually happens to the auditory cortex when you visually deprive an animal?'” Lee, my co-author, has been studying plasticity in the visual cortex for many years and I have been studying the auditory and visual cortex. We asked corresponding author Patrick Kanold, a professor of biology at the University of Maryland, if he’d been listening to Ray Charles or Art Tatum, but he told us the study originated in curiosity about how the brain changes over time. To document the effects, scientists measured changes in connections between different parts of the brain needed for hearing. Now we learn about hearing improvements in mice that, having left the critical period, lived one week in darkness. Early in life, during the “critical period,” the brain has astounding ability to make changes and connections that are necessary for many types of learning.
Musicians who were blind from birth, or at a young age, are renowned for awesome memory of songs and perfect pitch.Īge matters.
Scientists have known that the brain regions that normally support the lost sense of vision can be press-ganged into serving a surviving sense, like hearing.