Vision Clinical Trial
Official title:
GABA Levels in the Occipital Cortex of Blind Human Subjects
In blind individuals, the occipital cortex becomes capable of processing tactile and auditory
information, a phenomenon described as crossmodal plasticity. GABA is the major inhibitory
neurotransmitter in the brain and a possible candidate to mediate this form of human
plasticity. We intend to use magnetic resonance spectroscopy (MRS) to measure GABA and
hypothesize that GABA levels in the occipital cortex of blind humans will be lower than in
sighted controls. Such decrease could possibly mediate compensatory changes in the occipital
cortex of the blind.
Objective
Early blind subjects exhibit better tactile acuity than late blinds or sighted individuals.
The purpose of the study is the determine GABA levels in the human occipital cortex after
long-term light deprivation (blindness).
Study Population
Our experiments will make use of early blind, late blind, and sighted control subjects.
Design
Subject will be identified and will receive clinical and neurological examinations at the
NIH. MRS studies will be performed at NIH MRI Center with 3Tesla Magnet. Each subject head
will be positioned in an adjustable holder (designed for minimal motion and maximal comfort)
such that a flat coil lay just below the occipital cortex. The sequence has been described
before [33]. The individuals who perform the data analysis will be blind to the purpose of
the experiments.
Outcome measures
The concentration of GABA from the 14 ml voxel over the visual cortex will be measured.
Edited proton spectrum of GABA will be compared with the edited sub spectrum of creatine for
a concentration reference.
In blind individuals, the occipital cortex becomes capable of processing tactile and auditory
information, a phenomenon described as crossmodal plasticity. GABA is the major inhibitory
neurotransmitter in the brain and a possible candidate to mediate this form of human
plasticity. We intend to use magnetic resonance spectroscopy (MRS) to measure GABA and
hypothesize that GABA levels in the occipital cortex of blind humans will be lower than in
sighted controls. Such decrease could possibly mediate compensatory changes in the occipital
cortex of the blind.
Objective
Early blind subjects exhibit better tactile acuity than late blinds or sighted individuals.
The purpose of the study is the determine GABA levels in the human occipital cortex after
long-term light deprivation (blindness).
Study Population
Our experiments will make use of early blind, late blind, and sighted control subjects.
Design
Subjects will be identified and will receive clinical and neurological examinations at the
NIH. MRS studies will be performed at NIH MRI Center with 3Tesla Magnet. Each subject head
will be positioned in an adjustable holder (designed for minimal motion and maximal comfort)
such that a flat coil lay just below the occipital cortex. The sequence has been described
before. The individuals who perform the data analysis will be blind to the purpose of the
experiments.
Outcome measures
The concentration of GABA from the 14 ml voxel over the visual cortex will be measured.
Edited proton spectrum of GABA will be compared with the edited sub spectrum of creatine for
a concentration reference.
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