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CIMIT Summer Education Series 2007
Neurotechnology: Translating Basic Discoveries into Clinical Promise

7.31.2007:

Functional MRI and Brain Plasticity

SPEAKER: John Gabrieli, PhD: MIT


Inducing and Imaging Brain Plasticity

SPEAKER: Gottfried Schlaug, MD, PhD: BIDMC, HMS

 

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  • Summary 1
  • Summary 2
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Series Concludes with Discussion of Brain Plasticity

The fourth in the July series of Forums focused on neurotechnology concluded July 31 at a standing-room-only program at the MIT McGovern Institute for Brain Research.

The series was called “Neurotechnology: Translating Basic Discoveries into Clinical Promise.” Organizers of the four-session program were Charles Jennings, PhD, director of the McGovern Institute of Neurotechnology (MINT) Program, and Steven Schachter, MD, professor of neurology at Harvard Medical School; director of research, Department of Neurology, Beth Israel Deaconess Medical Center; associate director, clinical research, Harvard Medical School Osher Institute; CIMIT Program Leader, neurotechnology; and CIMIT Site Miner, BIDMC.

Presenting were John Gabrieli, PhD, Grover Hermann Professor of Health Sciences and Technology and Cognitive Neuroscience, MIT; director, Athinoula A. Martinos Imaging Center, McGovern Institute of Brain Research; and co-director, MIT Clinical Research Center; and Gottfried Schlaug, MD, PhD, associate professor of neurology; chief, Division of Cerebrovascular Disease, director, Music and Neuroimaging and Stroke Recovery Laboratories, BIDMC and Harvard Medical School.

Dr. Schlaug spoke on the topic of “Inducing and Imaging Brain Plasticity: Health Subjects and Patients Recovering from Stroke.” He said stroke recovery studies have shown that peri-lesional regions on the opposite hemisphere can either substitute for some of the lost function or be involved in the development of alternative strategies for impairment.

Dr. Schlaug’s studies sometimes use music as a means of prompting activity manifested from use of specific parts of the brain. He showed clips of a man who could not speak intelligibly. But when he was asked to sing the same words (while tapping his left hand), he was able to articulate the words that eluded him in speech.

Dr. Schlaug said such probing of parts of the brain have the potential to aid stroke victims in their attempts to regain speaking skills.

He also said non-invasive brain stimulation tools are now available to enhance desired brain changes, or depress unwanted or maladaptive brain changes.

Dr. Gabrieli spoke on the topic of “Functional Imaging of Human Brain Plasticity.”

He said that functional magnetic resonance imaging (fMRI) can reveal experience-dependent brain plasticity that can be seen in healthy people gaining new skills and in dyslexic children given remediation for reading difficulty.

Functional MRI and Brain Plasticity

The human brain is highly plastic, continually undergoing experience-dependent alterations in structure and function.  These changes, which are essential to learning, can be studied at many levels, from that of neurons to that of brain-wide networks.  Functional Magnetic Resonance Imaging (fMRI), which measures vascular changes in the brain associated with local neural activity, does not provide sufficient spatial or temporal resolution to study the behavior of individual neurons or even groups of neurons, but fMRI but can be used to measure how broad patterns of brain activity change over time.   

FMRI studies are extremely common in the field of neuroscience, and the most effective studies go beyond establishing correlations and provide information about how the brain processes information.  In one study led by Dr. Gabrieli of MIT, for example, experimenters were able to show that as people practice the task of mirror-reading, their brains gradually abandon spatial processing pathways in favor of linguistic ones.

Dr. Gabrieli and his team have also attempted to use fMRI to shed light on the causes of dyslexia, unexplained reading difficulties that affect five to ten percent of children.  Most dyslexic children possess normal verbal communication skills, so many researchers have assumed that dyslexia involves deficits in the visual processing of written words.  Dr. Gabrieli’s work, however, indicates that dyslexia may also be caused by deficits in speech processing.  When one compares fMRI images of the brains of dyslexic children to those of normal children, it appears that the brains of dyslexic children do not map letters to sounds, and vice versa, in a normal manner.  One training program designed to improve the “phonemic awareness” of dyslexic children showed promise in early trials. 

FMRI can also be used to study the progression of Alzheimer’s disease.  Many researchers believe that the brain begins to change ten to fifteen years before a patient can be diagnosed with Alzheimer’s, and most Alzheimer’s patients have sustained extensive brain damages by the time they are diagnosed with the disease.  The early identification and treatment of people at risk for Alzheimer’s disease could slow the progression of the disease while there is still time for these people to lead almost normal lives.  People with symptoms known to often precede Alzheimer’s are said to display “mild cognitive impairment,” and fMRI studies have shown that computer-based training regimes can significantly slow hippocampal degradation in these patients.

Finally, the Gabrieli lab has used fMRI to help people control activity in certain brain areas.  FMRI enabled the experimenters to provide each subject with feedback about the activity of a certain area of his or her brain associated with perception of subjective pain.  Subjects were instructed to raise and lower the level of activity in this area, and periodically, they were exposed to invariant thermal shocks.  With practice, subjects began to perceive the shocks as less painful or more painful depending on whether they were trying to lower or raise the activity in their subjective-pain brain areas.  In a small pilot study involving patients with chronic pain syndrome, practice with the feedback device seemed to reduce the pain that patients perceived.

All these results indicate that fMRI technology is a useful tool for understanding clinically relevant consequences of brain plasticity

 

Inducing and Imaging Brain Plasticity

The plasticity of the human brain is vital to learning and to the brain’s ability to recover after it is damaged.  Studying how brain plasticity can be induced promises to help guide therapies aimed at stroke patients and at others who have suffered brain damage.

The lab of Dr. Gottfried Schlaug is seeking to understand how the brain changes as a person learns to play a musical instrument.  Playing an instrument is a multimodal skill practiced over the course of a lifetime.  Dr. Schlaug’s group is in the midst of a longitudinal study that uses imaging techniques, including functional magnetic resonance imaging (fMRI), to measure how musical training affects the ability of children to discriminate between different melodies and rhythms.  The young musicians devote far less time to practice than do many older performers, but early results indicate that as little as sixteen months of musical training is sufficient to cause structural changes in their right motor cortices. 

The Schlaug lab is also seeking to use music to induce plastic responses in the brains of patients suffering from aphasia, the inability to speak normally.  In a person with aphasia, the brain attempts to compensate for the damage it has sustained through enhanced activity in either the perilesional cortex or in the right hemisphere.  Activity in the right hemisphere can be promoted by movement of the left hand or by thinking about melodic intonation.  Dr. Schlaug’s team devised an intense therapeutic method in which aphasic patients were asked to sing words that they could not speak and to simultaneously tap their left hands.  For nine patients who participated in a pilot study, the “melodic intonation therapy” caused improvements that persisted for at least four weeks after the therapy concluded.

Finally, Dr. Schlaug is interested in using transcranial direct current stimulation (tDCS) to promote motor recovery in patients with motor deficits.  FMRI research suggests that brain damage in one hemisphere disinhibits the healthy hemisphere, which in turn excessively inhibits the damaged hemisphere.  This excessive inter-hemispheric inhibition can prevent motor recovery.  TDCS can be used to reduce activity in the healthy hemisphere, and in early studies, it appears that tDCS in combination with occupational therapy is more effective at promoting motor recovery than occupational therapy alone. 

The work of Dr. Schlaug’s lab suggests that therapies designed to influence or even induce plastic responses in the brain may eventually prove effective against a wide range of mental problems.  In the future, imaging techniques may help doctors tailor individual treatment strategies and monitor the effects of different therapies and. 

 

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