The Treatment of Akinesia using Virtual Images

by Jerrold D. Prothero

T.R.'s Summary

In a letter to Suzanne Weghorst dated May 20th, 1993, T.R. provided us with his impression of his trials with the VV Sport display and laser pointer.

I thought I would just give you my impressions of my two days at your facility. I have purchased a laser light and have been practicing my new skills. Currently I am about at the same point as when you last saw me.

Prior to visiting the HIT lab my chief complaint was akinesia while unmedicated or during frequent off periods. I was almost completely immobile in this state relative to ambulation. I could take slight festinating steps of 3 -- 4 inch length. I believe the experience at HIT has enabled me to ``learn'' new motor skills which hopefully will continue to grow as I exercise them. Currently my unmedicated ambulatory skills are as follows. About 80% of the time I can initiate ambulation via conscious effort by targeting a spot that forces me to extend my stride length beyond its normal range. After that I can establish a steady cruising gait about 60% of the time. I can maintain that gait, intermittently, on an unconscious, automatic level which shifts to a conscious level when external stimuli invade such as approaching obstacles or turns in direction. This ambulation breaks down frequently as a result of external stimuli and has to be re-established. It is also difficult to initiate in an obstructive (e.g. a doorway or a short hallway) environment. Acceleration and deceleration is also disruptive. It seems that changes in speed are best accomplished by slowing down the speed of the stride without shortening its length.

Ambulation with tangible cues (or presumably virtual images of tangible cues) is still easier, and more reliable. A grid of playing cards spaced 26--28 inches apart allows me omnidirectional ambulation with ease albeit on a conscious level. This type of cued ambulation is much less fragile relative to external stimuli and consequently allows easier navigation around obstacles. However, the necessity to remain in the fully conscious mode is a drawback. Any significant inattention to the cue results in breakdown of ambulation.

In a telephone conversation with Dr. Carolyn Tanner of the Calif. Parkinson's Research Center (who has done extensive research on P.D.), she expressed her opinion that the above findings, if valid, were unique and qualitatively different. She was very interested to learn more about the VV glasses.

training stages:

1.

real world visual cues (playing cards)

2.

VV glasses with various scrolling images

3.

VV glasses with scrolling images plus real world static initiating cue

4.

as in step 2 but with mental extrapolation of scrolling image to provide initiating cue

5.

laser light pen as static initiating cue

6.

laser light pen as kinetic initiating cue (scrolling the target to my feet)

7.

chasing the light pen spot (target is about 26-28 inches in front of feet)

8.

7 but turning off the light pen after gait is established

9.

unassisted ambulation conscious attention to stride length

10.

9 with periods of automatic gait

11.

? total automatic gait (as yet unattainable)

In spite of my apparent progress ambulation remains extremely vulnerable to external stimuli and thus breaks down frequently. I have great difficulty inside my home, negotiating around tight corners and kitchen chairs. However, yesterday at the local high school track I was able to walk and then run a 1/4 mile without difficulty. Even full sprinting was possible. Visual cue walking remains significantly superior relative to initiating and sustaining gait, and ignoring external stimuli. If these limitations cannot be overcome by practice, then I believe the Virtual Vision glasses are by far the best option for trying to deal with this problem.

The following are a couple of suggestions as to what I believe would make the Virtual Vision glasses effective.

1.

the screen must superimpose over the entire southern hemisphere of the field of vision

2.

``objects'' should be spaced at simulated stride length in the foreground

3.

as a substitute for a scrolling image, a stroboscopic on/off effect might be effective.

Thank you again for all your efforts on my behalf.

At the time he wrote the above letter, he felt that he had learned something fundamentally new. He thinks now that it was more a working out of a latent potential, which he could have achieved in some other way.

Unfortunately, while T.R.'s new ambulatory skills lasted for a couple of months, they seem to have been removed by the general advance of his disease. Despite the advance in severity of his akinesia, however, the strong visual cuing effect remains intact. This is to be expected if one accepts the theory that visual cues bypass the basal ganglia (see Appendix C).

T.R.'s suggestions regarding an improved VV Sport display for prosthetic purposes are discussed in Subsection 6.4.1.