Sensory Experience Reshapes Adult Brains

The fifth chapter of “Train Your Mind, Change Your Brain” is concerned with how sensory experience reshapes adult brains.  Pascual-Leone and his colleagues wanted to see what would happen if sighted adults suddenly lost their vision, so they conducted a blindfold experiment.  They recruited people with normal vision and blindfolded them.  These volunteers were blindfolded all day, every day, from a Monday morning to a Friday evening.  With this sudden, new disability, these volunteers were able to get around their rooms at Beth Israel Deaconess Medical Center In Boston, by touch and sound with only a minimum number of bruises.

Before the enforced blindness, the visual cortices of the volunteers only showed activity when they looked at something.  However, after a mere five days of enforced unemployment, the visual cortex started taking on new tasks.  According to fMRI readings, they were handling tactile and auditory information.  When the volunteers listened to tones to determine whether their pitch was the same or different, or when they fingered Braille symbols, their “visual” cortices became active.  Pascal Leone said that five days was not long enough to establish new neuronal connections.  Pascal-Leone said, “some rudimentary somatosensory and auditory connections to the visual cortex must already be present” left over from brain development when neurons from the eyes and ears and fingers connect to many regions of the cortex rather than just the ones they’re supposed to.  Regardless of age, faced with sensory deprivation like blindness or deafness, the brain taps its power of neuroplasticity to reorganize, using the sensory inputs it it does have.

One of the more impressive examples of neuroplasticity  can be found with stroke patients.  Edward Taub developed a therapy that came to be known as constraint-induced movement therapy.  This therapy involves putting the stoke patient’s good arm in a sling and her good hand in an oven mitt so she could not use either.  So if she wanted to hold something or feed herself, get dressed, or do the laborious rehabilitation exercises through which he puts patients, she ended to use her damaged arm.  The rehab had community was united in opposition to this ideas that therapy after a stroke could reverse the neurological effects of the stroke.  The official position of the American Stroke Association was that rehab for patients with chronic stroke only increases a patient’s muscular strength and confidence, but does nothing to address brain damage.

After just ten days of therapy Taub found that patients regained significant use of an arm they thought would always hang uselessly.  They could put on a sweater, unscrew a cap on a jar, and pick up a bean on a spoon and put it into their mouth.  They could perform almost twice as many of the routines of daily living as patients who served as the controls and did not receive therapy.  This therapy worked even for patients who started the therapy more than a year after suffering their stroke.

Another study in which twenty-one patients received constraint-induced therapy showed large improvements in the quality and use of their impaired arm compared to the control group.  Two-years later, the constraint-induced group had retained their edge and were able to use their impaired arm, which was hardly impaired at this point, significantly mor and better than those who did not received this training.

One of the drawbacks of this training is that it is extremely time-consuming.   Consequently Taub and his colleagues developed what he calls AutoCITE, for automated constrain-induced therapy extension.  Research evaluating this remote system has produced favorable results.

The brain is undergoing continuous change as connections between one neuron and another are formed to establish memories.  But neuroplasticity goes beyond that.  It produces wholesale changes in the job functions of particular areas of the brain.  Cortical real estate that use to serve one purpose is reassigned and begins to do another.The brain remakes itself through life, in response to outside stimuli—to its environment and experience

As Taub sees it, neuroplasticity is evolution’s way of letting the brain break the bonds of “of its own genome,” escaping its initial organization.  The brain is neither immutable nor static, but is instead continuously remodeled by the lives we lead.  However, there is a catch.  These changes occur only when the person is paying attention to the input that causes them.  So attentional process are key to neuroplasticity.

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