Role of Brain Region Changes in Tactile (Touch) Ability Following Nerve Block
| Status: | Completed |
|---|---|
| Conditions: | Healthy Studies |
| Therapuetic Areas: | Other |
| Healthy: | No |
| Age Range: | 18 - Any |
| Updated: | 4/21/2016 |
| Start Date: | December 2001 |
| End Date: | December 2007 |
Substrates Mediating Deafferentiation-Induced Enhancement of Tactile Spatial Acuity
This study will examine the role of different brain regions in tactile (touch) ability after
application of a tourniquet (inflated blood pressure cuff). When the forearm is deprived of
blood for a short period of time, tactile ability in the other hand improves. This study
will try to learn what causes this improvement.
Healthy normal volunteers are eligible for this study. Candidates will have a brief medical
history and physical examination.
Volunteers will undergo two experiments, described below, that involve the following
procedures:
- Ischemic nerve block - A blood pressure cuff is inflated for 35-40 minutes around the
elbow area (also around the calf for Experiment 2 - see below). The resulting numbness,
tingling, loss of muscle strength, and discoloration of the forearm and hand disappear
within minutes after the cuff is deflated.
- Magnetic resonance imaging (MRI) - This test uses a magnetic field and radio waves
instead of X-rays to produce images of brain structure and function. The volunteer lies
on a stretcher that is moved into the scanner (a cylinder containing a strong magnet),
wearing earplugs to protect the ears from loud thumping noises that occur with
electrical switching of radio frequency circuits. The subject can communicate with an
investigator by intercom at all times during the scan.
- Transcranial magnetic stimulation (TMS) - An insulated wire coil is placed on the
patient's scalp. A brief electrical current passes through the coil, creating a
magnetic pulse that travels through the scalp and skull and causes small electrical
currents in the outer part of the brain. The stimulation may cause muscle hand or arm
twitching or transient tingling in the forearm, head or face muscles.
- Tactile spatial acuity testing - The subject's left arm is placed in a cast and the
left index finger is immobilized for this test which involves identifying the direction
of grooves applied to the finger.
Experiment 1
This experiment measures changes in tactile acuity and brain activation following cuff
inflation. The subject lies in the MRI scanner, with the left arm immobilized. Tactile
acuity is measured repetitively at the left index finger during placement and inflation of a
pressure cuff around the right forearm. The experiment consists of two sessions with the
cuff around the forearm and one with the cuff around the calf and lasts from 90 minutes to 2
hours.
Experiment 2
This experiment measures changes in tactile acuity linked to TMS stimulation. The subject
sits in an armchair with the left arm immobilized. Tactile acuity is measured repetitively
at the left index finger during placement and inflation of a pressure cuff around the right
forearm. In addition, TMS pulses (about one pulse per second) are delivered at different
locations over the right side of the head for up to 30 minutes. The experiment consists of
10 separate sessions on different days, each lasting about 1 hour.
application of a tourniquet (inflated blood pressure cuff). When the forearm is deprived of
blood for a short period of time, tactile ability in the other hand improves. This study
will try to learn what causes this improvement.
Healthy normal volunteers are eligible for this study. Candidates will have a brief medical
history and physical examination.
Volunteers will undergo two experiments, described below, that involve the following
procedures:
- Ischemic nerve block - A blood pressure cuff is inflated for 35-40 minutes around the
elbow area (also around the calf for Experiment 2 - see below). The resulting numbness,
tingling, loss of muscle strength, and discoloration of the forearm and hand disappear
within minutes after the cuff is deflated.
- Magnetic resonance imaging (MRI) - This test uses a magnetic field and radio waves
instead of X-rays to produce images of brain structure and function. The volunteer lies
on a stretcher that is moved into the scanner (a cylinder containing a strong magnet),
wearing earplugs to protect the ears from loud thumping noises that occur with
electrical switching of radio frequency circuits. The subject can communicate with an
investigator by intercom at all times during the scan.
- Transcranial magnetic stimulation (TMS) - An insulated wire coil is placed on the
patient's scalp. A brief electrical current passes through the coil, creating a
magnetic pulse that travels through the scalp and skull and causes small electrical
currents in the outer part of the brain. The stimulation may cause muscle hand or arm
twitching or transient tingling in the forearm, head or face muscles.
- Tactile spatial acuity testing - The subject's left arm is placed in a cast and the
left index finger is immobilized for this test which involves identifying the direction
of grooves applied to the finger.
Experiment 1
This experiment measures changes in tactile acuity and brain activation following cuff
inflation. The subject lies in the MRI scanner, with the left arm immobilized. Tactile
acuity is measured repetitively at the left index finger during placement and inflation of a
pressure cuff around the right forearm. The experiment consists of two sessions with the
cuff around the forearm and one with the cuff around the calf and lasts from 90 minutes to 2
hours.
Experiment 2
This experiment measures changes in tactile acuity linked to TMS stimulation. The subject
sits in an armchair with the left arm immobilized. Tactile acuity is measured repetitively
at the left index finger during placement and inflation of a pressure cuff around the right
forearm. In addition, TMS pulses (about one pulse per second) are delivered at different
locations over the right side of the head for up to 30 minutes. The experiment consists of
10 separate sessions on different days, each lasting about 1 hour.
Acute deafferentation in one hand leads to improvements in tactile discriminative skills in
the other, non-deafferented hand. This phenomenon, recently identified in our laboratory,
represents an adaptive, behaviorally important consequence of deafferentation. It
demonstrates that acute loss of sensory input from one hand results in rapid improvement of
skills in the remaining hand. The first experiment in this protocol seeks to identify
cortical regions activated in association with this improvement in tactile spatial acuity.
In the second experiment, we will determine the effects of transient inactivation of focal
cortical regions on this behavioral gain. While the first experiment will characterize brain
regions activated in association with this performance improvement, the second experiment
will provide information on the functional role of these regions. Understanding the
substrates that mediate this behavioral gain may be important for the design of strategies
to enhance them.
the other, non-deafferented hand. This phenomenon, recently identified in our laboratory,
represents an adaptive, behaviorally important consequence of deafferentation. It
demonstrates that acute loss of sensory input from one hand results in rapid improvement of
skills in the remaining hand. The first experiment in this protocol seeks to identify
cortical regions activated in association with this improvement in tactile spatial acuity.
In the second experiment, we will determine the effects of transient inactivation of focal
cortical regions on this behavioral gain. While the first experiment will characterize brain
regions activated in association with this performance improvement, the second experiment
will provide information on the functional role of these regions. Understanding the
substrates that mediate this behavioral gain may be important for the design of strategies
to enhance them.
- INCLUSION CRITERIA:
Normal volunteers who are willing and able to remain relaxed and immobile during active
scans, for a period of up to 2 hours.
EXCLUSION CRITERIA:
Subjects with: metal in the cranium except for crowns or fillings in mouth and permanent
metal dental braces, metal fragments from occupational exposure or surgical clips in or
near the brain.
Subjects with eye, blood vessel, cochlear or eye implants, with increased intracranial
pressure as evaluated by clinical means, with cardiac or neural pacemakers, intracardiac
lines and/or implanted medication pumps.
Subjects with large hemorrhagic or brain stem stroke.
Subjects with multiple cerebral lesions with residual deficits.
Subjects with history of head injury with loss of consciousness.
Subjects with history of severe alcohol or drug abuse or psychiatric illness.
Subjects with unstable cardiac dysrhythmia or unresponsive arterial hypertension (greater
than 160/100 mmHg).
Subjects with history of hyperthyroidism or individuals receiving drugs acting primarily
on the central nervous system or disorders of the blood coagulation system.
Subjects with excessive callus at their fingers.
Preganant women will be excluded from the study.
SUBJECTS DISCONTINUATION CRITERIA:
Subject's poor compliance with protocol evaluations or examinations and subject's request
to withdraw.
We found this trial at
1
site
9000 Rockville Pike
Bethesda, Maryland 20892
Bethesda, Maryland 20892
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