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B. NEURAL CORRELATES OF VIBRISSA RESONANCE

B. NEURAL CORRELATES OF VIBRISSA RESONANCE

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1521_book.fm Page 246 Tuesday, April 5, 2005 12:20 PM



Somatosensory (SEF) Responses: Lip



Normal healthy subject:



FHd Severe: Short

latency, high amplitude



FHd Mild; Long latency,

short amplitude



FIGURE 11.4 Somatosensory Evoked Responses Using MEG: The Lip. There were no

differences in latency or amplitude of somatosensory evoked responses for normal subjects

and subjects with focal hand dystonia based on mapping an uninvolved area. From Byl, N.N.,

Nagarajan, S.S., Merzenich, M.M., Roberts, T., McKenzie, 2002. Correlation of clinical neuromusculoskeletal and central somatosensory performance: variability in controls with patients with severe and

mild focal hand dystonia. Neural Plasticity 9:177–203. With permission.



on the affected side (mean latency ranging from 30 to 60 msec and the mean

amplitude ranging from 20 to 119 fT). There was a negative linear trend of amplitude

by latency for the digits on the unaffected side for FHd subjects and all of the

controls (as the latency increased, the amplitude decreased.

The field evoked firing patterns for controls and those with dystonia (mild and

severe) were similar when measured on an unaffected part, the lip. (Figure 11.4)

However, integrating amplitude by latency, those with severe dystonia had a significantly higher amplitude than those with mild dystonia. Those with severe dystonia

had a short latency and a high amplitude and those with mild dystonia had a long

latency and a low amplitude. (Figure 11.5) Bilaterally, the volume of the representation of the hand for those with mild dystonia was larger than the volume for

subjects with severe dystonia.

There were high, significant correlations (0.9029 affected and 0.8477 unaffected;

p<0.001, respectively) between dystonia severity and the SEF ratio of amplitude to

latency. On the affected side, there were negative correlations between SEF ratio and

dystonia severity with musculoskeletal performance, motor control on the target task

and fine motor skills. FHd subjects with mild dystonia tended to have a low SEF

ratio and demonstrated higher performance on these tasks than those with severe

dystonia. There was a significantly negative correlation between fine motor skills and

SEF ratio on the affected side; those with a high SEF ratio of amplitude to latency

demonstrated greater inaccuracy. On the unaffected side, there was a significant,

moderately positive correlation between the severity of dystonia performance on the

target task; with mild dystonia having lower performance scores on the target task.



© 2005 by Taylor & Francis Group.



1521_book.fm Page 247 Tuesday, April 5, 2005 12:20 PM



Somatosensory Evoked Field

Responses

D. Control - Affected Digit



A. Control - Unaffected Digit



200



200



100



100



0



0



–100



–100



–200

–100



0



100



200



–200

–100



0



100



G



120

FHD-Affected side-Affected Digit

Control

100

p<0.01

80

60

40

20

0

–20

0

20

40

60

80 100 120



140



H



120

FHD-Affected side-Affected Digit

Control

100

80

60

40

20

0

–20 0

20

40

60

80 100



120



140



I



120

FHD-Affected side-Affected Digit

Control

100

p<0.01

80

60

40

20

0

–20 0

20

40

60

80 100 120



140



200



B. FHD(Severe) - Unaffected Digit E. FHD(Severe) - Affected Digit



200



200



100



100



0



0



–100



–100

0



100



200



–200

–100



C. FHD(Mild) - Unaffected Digit



200



100



100



0



0



–100



–100



–200

–100



0



100



200



0



100



200



F. FHD(Mild) - Affected Digit



200



–200

–100



Meg. field (fT)



–200

–100



0



100



200



FIGURE 11.5 Somatosensory Evoked Responses Using MEG: The Hand. The subjects with

severe focal hand dystonia had a shorter latency and a higher amplitude on the involved digits

compared to normal subjects (B E compared to A and D). In addition, those with mild hand

dystonia had a longer latency and a lower amplitude than normal subjects (C and F compared

to A and D). Compared to controls, on the somatosensory evoked response, the affected digits

had a lower amplitude (G) but the somatosensory evoked response on the unaffected digits on

the affected side and the digits on the unaffected side of subjects with FHd was similar to normal

controls. From Byl, N.N., Nagarajan, S.S., Merzenich, M.M., Roberts, T., McKenzie, 2002. Correlation

of clinical neuromusculoskeletal and central somatosensory performance: variability in controls with patients

with severe and mild focal hand dystonia. Neural Plasticity 9:177–203. With permission.



2. Experiment II: Intervention (12 Subjects)

The purpose of this study was to assess the effectiveness of learning based sensorimotor training and recovery of task specific and sensory motor function in patients

with focal hand dystonia. Twelve subjects met the same criteria summarized in

Experiment I. A broad range of clinical tests were administered as in Experiment I.

The goals of treatment were to: 1. stop the learning of the abnormal movements

(stop performance on the target task); 2. use the hands in a stress-free way for all

activities (e.g., maintain carpal and oblique arches, initiate movement at MP joints

with lumbricals and interossei, avoid the lateral key pinch grip and forceful gripping,

let the sensory information from objects open the hand); 3. improve postural alignment with gravity and reduce adverse neural tension; 4. maximize flexibility in finger

spread, forearm rotation and shoulder rotation by decreasing muscle tension and



© 2005 by Taylor & Francis Group.



1521_book.fm Page 248 Tuesday, April 5, 2005 12:20 PM



releasing soft tissue adhesions; 5. facilitate positive health and healing (e.g., hydration, nutrition, and general exercise); 6. restore a positve self image regarding

performance on the target task; 7. quiet the hypersensitivity of muscle co-contractions when applying light and deep touch stimuli through the skin; 8. modify the

instrument as necessary to ease biomechanical stresses and facilitate the independent

control of the fourth and fifth digits of the left hand; 9. improve graded fine motor

movements and, most importantly, 10. restore the normal somatosensory representation of the hand in cortical area 3b to achieve normal sensory discrimination and

normal motor control. restore normal fine motor control on the target task

Subjects saw the physical therapist once a week (1–2 h) for supervised, learning

based sensorimotor training and were asked to be diligent with a home training

program. The intervention started with education about the condition of FHd and

the sensorimotor learning hypothesis for the etiology of FHd. The patients were

asked to stop all activities that caused abnormal finger movements of the left hand

(e.g., the target task as well as other work related tasks or activities of daily living).

To ease the tension in the postural muscles the subjects were instructed in diaphragmatic breathing, vestibular balance activities (eyes closed, head turning, unstable

static and dynamic support surfaces), calming (e.g., wrapping the arm and hand

tightly to the trunk for 5–15 minutes), passively maintaining the wrist and hand

into positions where the over-excitable extrinsic muscles were placed in a shortened

position (90–120 seconds) and practice using the hands in a stress free way. In

addition, the patients were instructed to carry out positive health and wellness

activities (good hydration, regular exercise, balanced diet). If the patient had musculoskeletal problems, then the home program included activities to improve flexibility, strength in the intrinsic hand muscles, and postural alignment in addition

to sensory retraining.

In each of the supervised sessions (1.5 h), 5–10 minutes were spent on soft

tissue mobilization and inhibitory positioning as needed to relieve the tension in

the affected limb, then 30–45 minutes were spent on supervised learning based

sensory motor training progressing from sensory discrimination activities, to sensory motor activities and then 10–20 minutes focused on selective fine motor

training on nontarget and target tasks using biofeedback (auditory or tape). The

sensory discrimination training focused initially on the involved fingers, with each

finger individually challenged on the distal pads as well as the dorsum and sides

of the fingers. Sensory discrimination activities were done with the patient in

different positions (supine, sitting or standing). Both passive and active stimulation

was used. The sensory motor activities included graded movements where sensory

information was used to control the hand (e.g., eyes closed, objects with different

surfaces [rough and smooth] introduced to the hand, explored and then used

appropriately). The fine motor tasks included instruction in stress free use of the

hand in common tasks such as picking up objects, doing activities of daily living

(ADLs), using the computer and ultimately playing the target instrument.

As part of the sensory retraining at home (at least 1 h/d), the patients were asked

to physically carry out sensory discrimination tasks, use a mirror of the unaffected

side to provide an image of the affected side which was out of sight behind the

mirror (Figure 11.6), use biofeedback to minimize cocontractions, and mentally



© 2005 by Taylor & Francis Group.



1521_book.fm Page 249 Tuesday, April 5, 2005 12:20 PM



Affected hand:

behind mirror



Unaffected hand:

in front of mirror



Right hand looks like left in mirror



FIGURE 11.6 Sensorimotor Mirror Training. While the subject looked at the mirror image

of the affected side, sensory and motor tasks were formed to provide positive feedback and

facilitate normal performance.



practice tasks such as: 1. the hand feeling normal; 2. the hand playing the instrument

normally and easily with appropriate speed and accuracy; 3. using eating utensils

normally; 4. writing without excessive gripping on the pen and moving the pen from

the elbow-shoulder; 5. doing detailed hand work; and 6. completing fine motor tasks.

Each subject was also encouraged to make a video of someone playing their instrument or doing tasks that they could view and imagine themselves doing the task.

As sensory processing skills improved, they were also asked to practice, small,

independent, isolated movements of the uninvolved and involved digits. If they

returned to instrumental play, they were asked to begin with new music.

This was a pre-experimental single group, prepost test study design with 12

subjects with FHd that participated in a controlled sensorimotor training program

for 6 months. All scores were reported descriptively and prepost test differences

were tested for significance using the paired Wilcoxon Test or the Paired t Test

depending on whether the dependent variables were ordinal or ratio scales.

a. Study Findings

All patients improved significantly on all parameters of clinical performance (25%

to 80%), bringing the performance of musculoskeletal parameters, sensory discrimination and fine motor control to the level of normal subjects. Task specific motor

control increased to 94%. All but two subjects returned to their previous work.

However, none gained 100% control of the hand. Rather, they still had to be careful



© 2005 by Taylor & Francis Group.



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