The Treatment of Akinesia using Virtual Images

by Jerrold D. Prothero

Glossary

Most of the medical definitions come from Taber [78].

ablate: To remove, especially by incision.

accommodation: The adjustment of the eye for various distances whereby it is able to focus the image of an object on the retina by changing the curvature of the lens.

adduction: Movement of a limb or eye toward median plane of body or, in case of digits, toward axial line of a limb.

akinesia: Complete or partial loss of muscle movement.

athetosis: Slow, writhing movements of the fingers and hands, and sometimes of the toes.

ballism: Violent, flailing movements.

basal ganglia: Five large subcortical nuclei (the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra) involved with controlling movement.

bradykinesia: Extreme slowness of movement.

brain stem: A joint term for the medulla oblongata, pons, and midbrain, which form a ``stem'' connecting the brain hemispheres to the spinal column.

cerebellum: Modulates motions and takes part in motor learning.

chorea: A nervous condition marked by involuntary muscular twitching of the limbs or facial muscles.

ciliary muscle: Smooth muscle whose contraction allows the lens of the eye to assume a more spherical shape, thus accommodating for near vision.

CT: Computed tomography.

dopamine: A neurotransmitter implicated in Parkinson's disease.

dyskinesia: See chorea.

dystonia: Impaired or disordered tonicity, esp. muscle tone.

festination: Abnormal and involuntary increase in speed of walking in an attempt to catch up with the displaced center of gravity due to the patient's leaning forward.

field-of-view: That portion of space which the fixed eye can see.

fovea: The central part of the visual field, approximately a degree across, which provides the sharpest vision.

freezing: See akinesia.

globus pallidus: One of the basal ganglia nuclei.

head-up display: A head-up display is one in which information is viewed superimposed on the outside world (as by displaying on a windscreen or visor) so that the information can be read with the head erect and with the outside world always in the field of view [2].

HITL: Human Interface Technology Laboratory.

HMD: Head-mounted display.

hypothalamus: Regulates autonomic, endocrine, and visceral functions.

kinesia paradoxa: Transient episodes of near-normal movement and of gait in particular in otherwise severely akinetic subjects [26].

LCD: Liquid crystal display.

L-dopa: See levodopa.

levodopa: A drug which has shown considerable effectiveness in treating Parkinson's disease. A form of a metabolic precursor of the natural neurotransmitter dopamine.

medulla oblongata: Lower part of the brain stem, controlling automatic functions such as digestion and breathing.

micrographia: A disorder in which a subject can begin writing normally, but in which the writing becomes increasingly small as the subject progresses.

midbrain: Connects the pons and cerebellum with the brain hemispheres. Controls various motor and sensory functions.

MRI: Magnetic resonance imaging.

myoclonus: Twitching or clonic spasm of a muscle or group of muscles.

nigrostriatal: Concerning a bundle of nerve fibers that connect the substantia nigra of the brain to the corpus striatum.

NTSC: A video signal standard established by the National Television Standards Committee.

on-off phenomenon: Changes in medical effect associated with varying levels of levodopa in the bloodstream.

oxidative stress: Overactivity of some biochemical pathway producing an excess of free radicals which react with and gradually destroy neurons.

Parkinson's disease: A chronic nervous disease characterized by a fine, slowly spreading tremor, muscular weakness and rigidity, and a peculiar gait.

pons: Connects the medulla oblongata and cerebellum to the upper portions of the brain.

Postencephalitic Parkinson's Disease: A form of Parkinson's disease which can be particularly potent and which can strike all age groups, caused by a viral infection. Epidemic between 1916 and 1927.

rigidity: tenseness; immovability; stiffness; inability to bend or be bent [78].

space stabilization: The illusion that a virtual object has a fixed location in space.

spinal cord: Center for reflex action, routing station for all nerves to the trunk and limbs.

stereopsis: Vision in which things have the appearance of solidity and relief as though seen in three dimensions, due to retinal disparity of images to the eyes.

stereotaxis: A method of precisely locating areas in the brain; use of this technique is essential in certain neurosurgical procedures.

striatum: Joint term for the caudate nucleus and putamen, which together form the input portion of the basal ganglia.

substantia nigra: One of the basal ganglia nuclei.

subthalamic nucleus: One of the basal ganglia nuclei.

thalamus: Receives all sensory input except olfactory. Serves as the interface from the rest of the central nervous system to the cerebral cortex.

tremors: Rhythmic, involuntary, oscillatory movements.

trophic: Concerned with nourishment. Applied particularly to a type of efferent nerves believed to control the growth and nourishment of the parts they innervate.

virtual environments: displays which attempt to present information in ways which are natural or intuitive to human users. Usually space-stabilized relative to the axis of orientation.

VV: Virtual Vision, Inc.

Virtual Vision, Inc.: A company started in 1992 which markets the Virtual Vision Sport.

Virtual Vision Sport: A head-mounted display consisting of a lens reflecting an LCD display mounted on a visor. The lens is mounted 24 below the line of sight of one eye and occludes 15 vertically by 22 horizontally of the visual field.