Brain Plasticity of Verbal Memory in the Blind
|First Received Date ICMJE||April 19, 2003|
|Last Updated Date||March 3, 2008|
|Start Date ICMJE||April 2003|
|Primary Completion Date||Not Provided|
|Current Primary Outcome Measures ICMJE||Not Provided|
|Original Primary Outcome Measures ICMJE||Not Provided|
|Change History||Complete list of historical versions of study NCT00059189 on ClinicalTrials.gov Archive Site|
|Current Secondary Outcome Measures ICMJE||Not Provided|
|Original Secondary Outcome Measures ICMJE||Not Provided|
|Current Other Outcome Measures ICMJE||Not Provided|
|Original Other Outcome Measures ICMJE||Not Provided|
|Brief Title ICMJE||Brain Plasticity of Verbal Memory in the Blind|
|Official Title ICMJE||Cross-Modal Plasticity of Verbal Memory in the Blind|
This study will examine whether blind people develop changes in the brain that improve memory function. Previous studies have shown that blind people, on average, perform better in memory tasks than sighted people. A possible reason for this is that parts of the brain that process visual information in sighted individuals are engaged in processing mnemonic (remembering) information in blind people.
Blind and sighted people 18 years of age and older are eligible for this study. Healthy, sighted individuals may participate in Part 1 of the study, which is designed to find appropriate words to use in tests for Part 2 of the study. Part 2 will include sighted people and blind people. It will examine whether the (visual) brain in blind people is processing mnemonic information in a way that helps with day-to-day memory functions. Blind participants in this study must have lost their sight by age 4. Candidates will be screened with a medical interview and examination and a brief test of short-term and long-term verbal memory. Sighted patients will also be tested for visual memory and for handedness.
Part 1 - Word Recognition Testing (2 sessions)
Part 2 - MRI Scanning and TMS Experiments (5 - 7 sessions)
Cross-modal plasticity refers to the concept that the cortex normally responsive to one sensory modality, when deprived of its usual input, becomes responsive to inputs from other sensory modalities. In blind subjects, the visual cortex processes somatosensory and auditory information. A recent functional imaging study found that verbal memory recall and verb generation significantly activated the primary visual cortex in early blind humans. The magnitude of occipital activation was positively correlated with subsequent performance on verbal memory and verb generation tasks. These results raised the untested hypothesis that the primary visual cortex may be the neural substrate mediating superior verbal memory performance in early blind individuals. The purpose of this protocol is to test this hypothesis.
The first experiment will identify the magnitude of activation in cortical areas associated with successful verbal memory encoding and retrieval, and with verb generation, in blind individuals and sighted controls. The expected outcome is increased involvement of the visual cortex in the early blind group. In the second experiment, we will test the hypothesis that disruption of activity of the activated visual cortex (using TMS) will have deleterious effects on verbal memory encoding and verb generation in early blind subjects, but not in late blind subjects nor sighted controls. The TMS experiment is necessary to identify a cause-effect link between occipital activation and improved memory performance.
Experiment 1: We plan to study early blind subjects, late blind subjects and sighted controls during encoding into and retrieval from episodic verbal memory, and during verb generation, using functional magnetic resonance imaging (fMRI). The primary outcome measure will be the number of voxels significantly activated in primary visual cortex in early blind subjects vs. late blind subjects and sighted controls. Experiment 2: We plan to apply rTMS over left primary visual cortex, left prefrontal cortex, and a control site during encoding of words into and retrieval of words from episodic memory (primary task), and during a verb generation task. Sighted volunteers, early blind and late blind subjects will be studied. The primary outcome measure will be performance on a memory test during rTMS applied to different sites in the different groups. This investigation is important because it can provide novel evidence on a hierarchically high function of the primary visual cortex in the blind.
|Study Type ICMJE||Observational|
|Study Design ICMJE||Not Provided|
|Target Follow-Up Duration||Not Provided|
|Sampling Method||Not Provided|
|Study Population||Not Provided|
|Intervention ICMJE||Device: Magstim Rapid Magnetic Stimulator|
|Study Group/Cohort (s)||Not Provided|
* Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
|Recruitment Status ICMJE||Completed|
|Completion Date||April 2005|
|Primary Completion Date||Not Provided|
|Eligibility Criteria ICMJE||
Early Blind Subjects: Only compliant early blind subjects who have lost their vision before age 4 years due to diseases affecting the peripheral components of the visual system, i.e., blind subjects without any further neurological problems, and with normal MRI scans, will be selected.
Late Blind Subjects: Only compliant late blind subjects who have lost their vision after age 4 years due to diseases affecting the peripheral components of the visual system, i.e., blind subjects without any further neurological problems, and with normal MRI scans, will be selected.
Sighted Controls: Only compliant adult healthy volunteers with no history of neurological and psychiatric illness who are able to concentrate and to perform simple attentional tasks are eligible.
Blind Subjects: Early and late blind subjects (aged 18 or over) will be included in this protocol. Handedness will be assessed by the Edinburgh inventory scale. All experimental sessions will be studied on outpatient basis.
Sighted Subjects: Healthy sighted (normal or corrected-to normal vision) matched in age, sex and level of education to the blind subjects. Handedness will be assessed by the Edinburgh inventory scale.
Exclusion criteria for the study will be any current medical or surgical condition or psychiatric or neurological illness. Furthermore, any individual who is on medication with potential influence on nervous system function, who has a history of surgery with metallic implants or known history of metallic particles in the eye, cardiac pacemaker, intracardiac lines, neural stimulators, cochlear implants, pregnancy, or history of drug abuse, will be excluded from the study.
|Accepts Healthy Volunteers||Yes|
|Contacts ICMJE||Contact information is only displayed when the study is recruiting subjects|
|Location Countries ICMJE||United States|
|NCT Number ICMJE||NCT00059189|
|Other Study ID Numbers ICMJE||030163, 03-N-0163|
|Has Data Monitoring Committee||Not Provided|
|Responsible Party||Not Provided|
|Study Sponsor ICMJE||National Institute of Neurological Disorders and Stroke (NINDS)|
|Collaborators ICMJE||Not Provided|
|Investigators ICMJE||Not Provided|
|Information Provided By||National Institutes of Health Clinical Center (CC)|
|Verification Date||April 2005|
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