Neurophysiology of Surround Inhibition in the Human Motor Cortex
| Status: | Recruiting |
|---|---|
| Conditions: | Healthy Studies |
| Therapuetic Areas: | Other |
| Healthy: | No |
| Age Range: | 18 - 70 |
| Updated: | 8/12/2018 |
| Start Date: | January 11, 2017 |
| End Date: | July 18, 2019 |
| Contact: | Elaine P Considine, R.N. |
| Email: | considinee@ninds.nih.gov |
| Phone: | (301) 435-8518 |
Detailed Evaluation of the Neurophysiology of Surround Inhibition in the Human Motor Cortex
Background:
Movement disorders have many different causes and symptoms. Researchers still do not fully
understand which parts of the brain are involved in fine movement. They want to learn about
which brain regions could be abnormal in people with movement disorders.
Objective:
To better understand how the brain controls movement.
Eligibility:
Healthy, right-handed adults age 18-70 years old.
Design:
Participants will be screened with a physical exam and questions about their handedness. They
may have a urine test.
Participants will have 1 or 2 clinic visits. The first visit will last about 1.5 hours. The
second will last about 3 hours.
Participants will have structural magnetic resonance imaging (MRI). A strong magnetic field
and radio waves take pictures of the brain. Participants will lie on a table that slides in
and out of a metal cylinder.
Participants may have transcranial magnetic stimulation. A wire coil is held on the scalp. A
brief electrical current is passed through the coil and creates a magnetic pulse that
stimulates the brain. Participants will wear a pair of glasses or a headband with small
sensors so researchers can track head position.
Participants will perform a simple index finger movement task.
Participants may have surface electromyography from at least two hand muscles. Small metal
disk or adhesive pad electrodes will be taped to the skin. Participants will be seated in a
comfortable chair with their hands placed on a pillow.
Participants may have an electroencephalography. A cap with small disc electrodes will be
placed on the scalp.
Movement disorders have many different causes and symptoms. Researchers still do not fully
understand which parts of the brain are involved in fine movement. They want to learn about
which brain regions could be abnormal in people with movement disorders.
Objective:
To better understand how the brain controls movement.
Eligibility:
Healthy, right-handed adults age 18-70 years old.
Design:
Participants will be screened with a physical exam and questions about their handedness. They
may have a urine test.
Participants will have 1 or 2 clinic visits. The first visit will last about 1.5 hours. The
second will last about 3 hours.
Participants will have structural magnetic resonance imaging (MRI). A strong magnetic field
and radio waves take pictures of the brain. Participants will lie on a table that slides in
and out of a metal cylinder.
Participants may have transcranial magnetic stimulation. A wire coil is held on the scalp. A
brief electrical current is passed through the coil and creates a magnetic pulse that
stimulates the brain. Participants will wear a pair of glasses or a headband with small
sensors so researchers can track head position.
Participants will perform a simple index finger movement task.
Participants may have surface electromyography from at least two hand muscles. Small metal
disk or adhesive pad electrodes will be taped to the skin. Participants will be seated in a
comfortable chair with their hands placed on a pillow.
Participants may have an electroencephalography. A cap with small disc electrodes will be
placed on the scalp.
Objectives:
The purpose of this protocol is to improve understanding of the neurophysiological mechanisms
that underlie the phenomenon of surround inhibition in the human motor cortex. It is known
that patients with focal hand dystonia have abnormal motor surround inhibition. However, the
physiology of this phenomenon still remains unclear. The 2 sub-studies proposed under this
protocol will integrate several neurophysiological techniques to explore different aspects of
motor surround inhibition. The objectives of sub-study 1 are (a) to identify the EEG
correlate of motor SI (b) to determine the relationship between short interval intracortical
inhibition (SICI) and SI, both of which are compromised in patients with FHD and (c) to
determine if there is an oscillatory frequency band that is relevant for SI. The results from
this sub-study will shed light on the inhibitory mechanisms that are critical for motor SI.
Sub-study 2 is aimed at determining the influence of parietal conditioning on motor surround
inhibition. If conditioning the parietal cortex enhances SI, we can conclude that the
parieto-motor inhibitory network may be involved in motor SI and that this network could be
affected in focal hand dystonia.
Study population:
We intend to study up to 65 healthy volunteers in total. Up to 30 participants will be
recruited for sub-study 1 and 35 for sub-study 2.
Design:
Sub-study 1: This will be an exploratory study. Participants will perform an auditory cued
index finger movement task and motor evoked potentials will be elicited by stimulating the
motor hotspot of a surround muscle using transcranial magnetic stimulation (TMS). EEG will be
recorded continuously. Single or paired TMS pulses (with postero-anterior or antero-posterior
current) will be delivered either while the subject is at rest or at movement onset.
TMS-evoked potentials (TEPs) will be obtained by time-locked averaging of all the trials in
each condition. The amplitudes of the different peaks of the TEP will be compared across
conditions which may be correlated with the degree of SI or SICI. The components of the TEP
that are most relevant to motor SI will thus be identified.
Sub-study 2: This will be a hypothesis-driven study. Our primary hypothesis is that parietal
conditioning will influence motor SI in healthy volunteers. Participants will perform an
auditory cued index finger movement task and motor evoked potentials will be elicited by
stimulating the motor hotspot of a surround muscle using transcranial magnetic stimulation.
Two coils, one positioned over the motor cortex and the other over an inhibitory region of
the inferior parietal lobule, will deliver TMS pulses at a fixed inter-stimulus interval. The
pulses will be delivered either while the subject is at rest or at movement onset. The ratio
of mean MEP amplitude obtained with parietal conditioning to that obtained with motor cortex
stimulation alone at movement onset will reveal any parieto-motor influence on SI.
Outcome measures:
For sub-study 1, our outcome measures will be (1) amplitudes of the different TEP peaks (2)
degree of surround inhibition and short interval intracortical inhibition (3) correlation
between them and relevant peak amplitudes (4) power and cortico-cortical coherence at
different frequency bands.
MEP amplitude will be the primary outcome measure in sub-study 2.
The purpose of this protocol is to improve understanding of the neurophysiological mechanisms
that underlie the phenomenon of surround inhibition in the human motor cortex. It is known
that patients with focal hand dystonia have abnormal motor surround inhibition. However, the
physiology of this phenomenon still remains unclear. The 2 sub-studies proposed under this
protocol will integrate several neurophysiological techniques to explore different aspects of
motor surround inhibition. The objectives of sub-study 1 are (a) to identify the EEG
correlate of motor SI (b) to determine the relationship between short interval intracortical
inhibition (SICI) and SI, both of which are compromised in patients with FHD and (c) to
determine if there is an oscillatory frequency band that is relevant for SI. The results from
this sub-study will shed light on the inhibitory mechanisms that are critical for motor SI.
Sub-study 2 is aimed at determining the influence of parietal conditioning on motor surround
inhibition. If conditioning the parietal cortex enhances SI, we can conclude that the
parieto-motor inhibitory network may be involved in motor SI and that this network could be
affected in focal hand dystonia.
Study population:
We intend to study up to 65 healthy volunteers in total. Up to 30 participants will be
recruited for sub-study 1 and 35 for sub-study 2.
Design:
Sub-study 1: This will be an exploratory study. Participants will perform an auditory cued
index finger movement task and motor evoked potentials will be elicited by stimulating the
motor hotspot of a surround muscle using transcranial magnetic stimulation (TMS). EEG will be
recorded continuously. Single or paired TMS pulses (with postero-anterior or antero-posterior
current) will be delivered either while the subject is at rest or at movement onset.
TMS-evoked potentials (TEPs) will be obtained by time-locked averaging of all the trials in
each condition. The amplitudes of the different peaks of the TEP will be compared across
conditions which may be correlated with the degree of SI or SICI. The components of the TEP
that are most relevant to motor SI will thus be identified.
Sub-study 2: This will be a hypothesis-driven study. Our primary hypothesis is that parietal
conditioning will influence motor SI in healthy volunteers. Participants will perform an
auditory cued index finger movement task and motor evoked potentials will be elicited by
stimulating the motor hotspot of a surround muscle using transcranial magnetic stimulation.
Two coils, one positioned over the motor cortex and the other over an inhibitory region of
the inferior parietal lobule, will deliver TMS pulses at a fixed inter-stimulus interval. The
pulses will be delivered either while the subject is at rest or at movement onset. The ratio
of mean MEP amplitude obtained with parietal conditioning to that obtained with motor cortex
stimulation alone at movement onset will reveal any parieto-motor influence on SI.
Outcome measures:
For sub-study 1, our outcome measures will be (1) amplitudes of the different TEP peaks (2)
degree of surround inhibition and short interval intracortical inhibition (3) correlation
between them and relevant peak amplitudes (4) power and cortico-cortical coherence at
different frequency bands.
MEP amplitude will be the primary outcome measure in sub-study 2.
- INCLUSION CRITERIA:
- Age between 18 - 70 years.
- Right-handed (tested by the Edinburg handedness inventory).
- Able to give informed consent.
- Able to comply with all study procedures.
- Abstain from alcohol for at least 48 hrs prior to the study and caffeine on the day of
the study (based on oral interview).
EXCLUSION CRITERIA:
- Illegal drug use within the past 6 months based on history alone. The intent is to
exclude those with drug use that may affect study results.
- Self-reported consumption of >14 alcoholic drinks/week for a man and >7 alcoholic
drinks/week for a woman.
- Abnormal findings on neurological examination.
- History of or current brain tumor, stroke, head trauma with loss of consciousness,
epilepsy or seizures.
- Current episode of major depression or any major psychiatric illness.
- Taking medications that act directly on the central nervous system such as
anti-epileptics, anti-histamines, anti-parkinsonian medication, muscle relaxants,
medication for insomnia, anti-depressants, anti-anxiety medication.
- Presence of any metal in the eye or skull area such as a brain stimulator, shrapnel,
surgical metal, clips in the brain, cochlear implants, metal fragments in the eye.
- Presence of pacemaker, intracardiac lines, implanted pumps or stimulators or metal
objects inside the eye or skull.
- Known hearing loss.
- NIH employees and/or staff.
- Pregnancy
EXCLUSION CRITERIA for MRI (sub-study 2 only):
We will follow the Clinical Radiology/NMR Center guidelines for MR safety.
Some of the exclusions are:
- Have non-MRI compatible metal in the body, such as a cardiac pacemaker, brain
stimulator, shrapnel, surgical metal, clips in the brain or on blood vessels, cochlear
implants, artificial heart valves or metal fragments in the eye as these make having
an MRI unsafe.
- Have metallic dental fillings which are likely to cause MRI artifacts
- Unable to lie flat on the back for the expected length of the experiment,
- up to 30 mins.
- Uncomfortable being in a small space for the expected length of the experiment, up to
30 mins.
- Pregnancy.
We found this trial at
1
site
9000 Rockville Pike
Bethesda, Maryland 20892
Bethesda, Maryland 20892
301-496-2563
Phone: 800-411-1222
National Institutes of Health Clinical Center The National Institutes of Health (NIH) Clinical Center in...
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