Efficacy of electrotactile vestibular substitution in patients with peripheral and central vestibular loss.

Vestibular dysfunction of either central or peripheral origin can significantly affect balance, posture, and gait. We conducted a pilot study to test the effectiveness of training with the BrainPort balance device in subjects with a balance dysfunction due to peripheral or central vestibular loss. The BrainPort balance device transmits information about the patient's head position via electrotactile stimulation of the tongue. Head position data is sensed by an accelerometer and displayed on the tongue as a pattern of stimulation. This pattern of stimulation moves forward, backward, and laterally on the tongue in direct response to head movements. Users of the device were trained to use this stimulation to adjust their position in order to maintain their balance. Twenty-eight subjects with peripheral or central vestibular loss were trained with the BrainPort balance device and tested using the following standardized quantitative measurements of the treatment effects: Computerized Dynamic Posturography (CDP) using the Sensory Organization Test (SOT), Dynamic Gait Index (DGI), Activities-specific Balance Confidence Scale (ABC), and Dizziness Handicap Inventory (DHI). All subjects had chronic balance problems and all but one had previously participated in vestibular rehabilitation therapy. The scores on the clinical tests upon entry into the study were compared to their scores following training with the BrainPort balance device. Our results exhibit consistent positive and statistically significant improvements in balance, posture and gait. These results exceed what could normally be achieved in three to five days of traditional balance training alone. Since this was not a controlled study, we are unable to distinguish the degree to which these improvements are attributable to training with the BrainPort balance device versus the balance exercises performed by all subjects as a part of the BrainPort training sessions. Nonetheless, after training with the BrainPort balance device, all subjects demonstrated significant improvements in performance beyond what might be expected from conventional vestibular rehabilitation therapy.

Efficacy of electrotactile vestibular substitution in patients with bilateral vestibular and central balance loss.

Patients with bilateral vestibular loss (BVL) of both central and peripheral origin experience multiple problems with balance and posture control, movement, and abnormal gait.Wicab, Inc. has developed the BrainPort balance device to transmit head position/orientation information normally provided by the vestibular system to the brain through a substitute sensory channel: electrotactile stimulation of the tongue. Head-orientation data (artificially sensed) serves as the input signal for the BrainPort balance device to control the movement of a small pattern of stimulation on the tongue that relates to head position in real-time. With training, the brain learns to appropriately interpret the information from the device and utilize it to function as it would with data from a normal-functioning natural sense. Ina total of 40 subjects trained with the BrainPort, 18 have been tested using standardized quantitative measurements of the treatment effects. A specialized set of exercises, testing, and training procedures has been developed that may serve as the course of intensive physical therapy with the BrainPort balance device. Our results demonstrate consistent positive and statistically significant balance rehabilitation effects independent of aging and etiology of balance deficit.

Brain plasticity: 'visual' acuity of blind persons via the tongue.

The 'visual' acuity of blind persons perceiving information through a newly developed human-machine interface, with an array of electrical stimulators on the tongue, has been quantified using a standard Ophthalmological test (Snellen Tumbling E). Acuity without training averaged 20/860. This doubled with 9 h of training. The interface may lead to practical devices for persons with sensory loss such as blindness, and offers a means of exploring late brain plasticity.

Theoretical and practical considerations in the restoration of function after stroke.

Recovery of function after stroke appears to include elements of both restoration and compensation. The brain is highly plastic, which allows reorganization after damage. Stroke produces permanent damage to the brain, so recovery must be based on activity in surviving cells that are either adjacent, contralateral, or in a different region. Furthermore, representation of a particular function in the brain is usually not limited to a single brain region. Multiple representation provides the opportunity for brain reorganization; functions are assumed by surviving brain structures. Compensation can be the initial response in the recovery phase and may persist through later phases because of the new habits formed (as the restraint therapy studies of Taub and others would suggest), because the damage to the brain is extensive and hinders restoration, because of secondary pathology, such as tendon shortening and muscle wasting, that does not allow brain reorganization to be translated into functional recovery, or because of inadequate (especially late) rehabilitation.

The cost of an action potential.

Neuronal modules, or 'cell-assemblies', comprising millions of mutually interconnected cells have been postulated to form the basis of many functions of the brain, such as mood, sleep, hunger, vigilance, and more. Depending on the extent of the module, neurocommunication in cell-assemblies might exceed metabolic resources. A medium-size (10000 neurons) module would require at least 10 J per l of brain, based on a calculated cost of an isolated action potential (AP) of 10(11)-10(12) molecules of ATP per cm(2) of cell membrane, with an absolute minimum of 10(6) ATP at a node of Ranvier. The figure matches the cost of depolarizing the unmyelinated axon of the large monopolar cell in the blowfly retina. A circuit model of the cell membrane, based on abrupt changes of Na(+) and K(+) conductances, is used to emulate the AP and to assess the resulting ionic unbalance. The cost of an AP is equated to the metabolic energy necessary to fuel ATP-based pumps that restore intracellular K(+). The high metabolic demand of a cell-assembly suggests that less expensive means of neurocommunication may be involved, such as non-synaptic diffusion neurotransmission (NDN), which would comply with a proposed law of conservation of space and energy in the brain.

Bases científicas de la rehabilitación neurológica tardía / Scientific bases of late neurological rehabilitation

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Theoretical aspects of sensory substitution and of neurotransmission-related reorganization in spinal cord injury.

Spinal cord rehabilitation has progressed enormously since World War II, and persons with spinal cord injuries now have long life expectancies. Research has recently concentrated on improvement of the quality of life, and on neural mechanisms of recovery. This article will explore some aspects of both of these areas. In the first section, the potential applications of sensory substitution systems for such functions as sex sensation and sensation from feet and from robotic hands will be examined. In the second section, the potential role of nonsynaptic diffusion neurotransmission (NDN) in neural reorganization after spinal cord injury will be considered. This article includes portions of previous publications and reports.

The grant portfolio of the National Center for Medical Rehabilitation Research: the first five years.

OBJECTIVE: To relate grant funding activities of the National Center for Medical Rehabilitation Research (NCMRR) with the Center's mission, priorities, and terminology for disability classification. STUDY DESIGN: Retrospective review by the National Advisory Board on Medical Rehabilitation Research (NABMRR). DATA: Abstracts of 153 research proposals and one contract funded by the NCMRR from 1992 through 1996. METHOD: A six-member research group participated in the development of a rating form and related instructions used to evaluate each abstract. The form was piloted and revised, and interrater agreement was monitored. RESULTS: Funded proposals reflected each of the NCMRR priorities evaluated, with the highest proportion in the areas of assistive technology and whole body system, and the lowest in the area of behavioral adaptation. Although some proposals were funded in each of the domains of the disability classification system, proportionately fewer addressed the domains of disability and societal limitations. Findings also indicated that few funded proposals addressed more than one domain in the disability classification system and that most abstracts did not address consumers' perspectives on quality of life. RECOMMENDATIONS: The NABMRR recommended that the NCMRR (1) encourage more research in the areas of disability and societal limitations and in behavioral adaptation, (2) examine funded proposals in light of a recent Institute of Medicine report, and (3) explore quality-of-life measurements. Further, members of the rehabilitation community are encouraged to e-mail their responses to this review to NCMRR staff at (1q2n@nih.govA) and to suggest areas of research emphasis.

Form perception with a 49-point electrotactile stimulus array on the tongue: a technical note.

Form perception with the tongue was studied with a 49-point electrotactile array. Five sighted adult human subjects (3M/2F) each received 4 blocks of 12 tactile patterns, approximations of circles, squares, and vertex-up equilateral triangles, sized to 4x4, 5x5, 6x6, and 7x7 electrode arrays. Perception with electrical stimulation of the tongue is better than with fingertip electrotactile stimulation, and the tongue requires 3% (5-15 V) of the voltage. The mean current for tongue subjects was 1.612 mA. Tongue shape recognition performance across all sizes was 79.8%. The approximate dimensions of the electrotactile array and the dimensions of compartments built into dental retainers have been determined. The goal is to develop a practical, cosmetically acceptable, wireless system for blind persons, with a miniature TV camera, microelectronics, and FM transmitter built into a pair of glasses, and the electrotactile array in a dental orthodontic retainer.

Brain cell microenvironment effects on neuron excitability and basal metabolism.

In a model of neurons in a brain cell assembly, changes in volume of the extracellular space affect neuronal excitability and basal metabolism. A widely applicable coefficient of excitability with respect to a variation of the volume fraction has been determined. Calculations suggest that chloride increases membrane stability by indirectly promoting an acceleration of the metabolic pumping rate as a response to a diminished extracellular volume fraction. Volume fraction changes induced by cell swelling in a compact and highly tortuous microenvironment may play a role in epilepsy and, following brain damage, in cell death and recovery.

Nerve length and volume in synaptic vs diffusion neurotransmission: a model.

Non-synaptic diffusion neurotransmission (NDN) may be an important factor in brain space and energy conservation, especially within cell assemblies and for mass sustained functions. We have illustrated the extreme cases of total synaptic and total ND neurotransmission for the purpose of noting the differences between the two. For these modeling studies, in which we assume assemblies of 1000 to 100 000 cells supplied by at least one fiber and a single synapse from each of the other cells, each cell assembly would have approximately 200 m to 8000 km of nerve fibers more than when innervated by diffusion. For coeruleo-cortical synaptic innervation, linking each to a common origin (the locus coeruelus), the fiber lengths are 38 cm (1000 cells) to 170 m (100,000 cells). It is likely , however, that neuronal arrays include both 'wireless' (NDN) as well as synaptic intercellular communication systems.

Non-synaptic diffusion neurotransmission: a novel concept for future migraine research.

The concept of non-synaptic diffusion neurotransmission (NDN) is reviewed. Evidence is presented that monoamine neurotransmission is largely by NDN. The role of NDN in pain and sleep is described and its relevance to migraine research is discussed.

The brain beyond the synapse: a review.

Several topics in contemporary neuroscience are treated in historical perspective. These include the localizationist-connectionist model of brain function and its influence on experimental neuroscience and clinical management of brain damaged persons; brain plasticity; the accumulating evidence for non-synaptic diffusion neurotransmission (NDN) as a major mechanism of information transmission in the brain; and the co-existence of plasticity and localization as well as of synaptic and non-synaptic mechanisms. The status of theory in the neurosciences is examined.

Stroke rehabilitation in Stockholm. Basis for late intervention in patients living at home.

In order to identify the basis of late-therapy intervention in patients with stroke, we studied a population-based sample of 20 patients. The requests were that they should be living at home 1-3 years after being hospitalized, and that they had declared themselves in need of rehabilitation services. The assessment of abilities and activities of the patients was related to the model of human occupation developed by Kielhofner and co-workers. Most individuals reported a change in activity and interest patterns after stroke, and high motivation in current activities. The cognitive functions were within normal limits for all tested patients. However, the motor abilities and verbal performances were frequently affected and varied considerably. About 3/4 of the patients were not motivated to change their level of dependence in personal and instrumental ADL. Social and leisure activities outside the home were identified as the most promising goals for community-based rehabilitation programmes. Focusing on such activities, potential improvement in quality of life for this population could be achieved by individually-planned rehabilitation programmes using non-professional collaborators and patient organizations.