Biomedical subjects

K L Kilgore

Publications and source records attributed to K L Kilgore.

25 records · Page 2Linked to original sources

PubMed1996

Tri-state myoelectric control of bilateral upper extremity neuroprostheses for tetraplegic individuals.

For the purpose of bimanual control of tetraplegic hands that have useful movement restored by a neuroprosthetic device, the use of myoelectric signals from bilateral sternoclei-domastoid muscles is proposed. Three state control has been proposed where each sternocleidomastoid controls its ipsilateral hand. Demonstration was made with spinal-cord-injured and nonspinal-cord-injured subjects providing three levels of activation that can be repeatably made with each of these muscles. The agonist and antagonist sternocleidomastoids during this command control were differentiated so that the desired hand will respond to a command. Neither normal head movements nor head position within its comfortable range of motion were shown to interfere with the proposed command. The provision of feedback was shown as important to provide robustness in the operation for the users selection of the right or left hand. The performance of spinal cord injured and noninjured persons using this controller was quantitatively measured through the completion of precision tracking tasks by the manipulation of on-screen virtual hands. All subjects were able to operate the controller with a degree of skill acceptable for completion of functional tasks with bilateral stimulated hand grasps. The sensitivity of the subjects performance to variation in controller parameters was also measured.

Arm↗

PubMed1993

Grasp synthesis for upper-extremity FNS. Part 1. Automated method for synthesising the stimulus map.

Functional neuromuscular stimulation (FNS) has been used in open-loop upper-extremity neuroprostheses to provide grasp and release for quadriplegic individuals. A principal issue in implementation of the open-loop neuroprosthesis is the synthesis of the grasp stimulus map, which is the relationship between the input control signal and the output stimulus applied to each electrode. The goal of this project was to develop a method of stimulus map synthesis which compensates for the influence of the electrode-position-dependent recruitment properties on the grasp output, and which can be performed using automated procedures. A method called the external moment grasp synthesis procedure (GSP) has been developed which meets these criteria. The GSP uses an external moment of model of the hand which describes the interaction between the active moments produced by electrical stimulation, the passive joint moments and the total joint moment and angle. The GSP was used to develop the stimulus map for three paralysed subjects, and in all cases the GSP-generated grasp patterns had lower errors than grasp patterns developed using the previously implemented rule-based method of stimulus map synthesis. The GSP was successfully implemented by computer and was able to compensate for the effects of the electrode recruitment properties on the grasp pinch force.

Electric Stimulation Therapy↗

PubMed1993

Grasp synthesis for upper-extremity FNS. Part 2. Evaluation of the influence of electrode recruitment properties.

Functional neuromuscular stimulation (FNS) has been used in upper extremity neuroprostheses to provide grasp and release for quadriplegic individuals. The goal of this project was to determine the electrode/muscle input/output characteristics with the greatest influence on the grasp output. This was evaluated by simulating the grasp synthesis procedure, using a model of the electrode/muscle output as a function of stimulus level and joint angle. The parameters of this model were determined from experimental data from 112 electrodes. The grasp output for 500 different modelled pairs of electrodes were analysed, with each pair consisting of a thumb flexor and a thumb extensor. The simulation results indicate that the most influential electrode input/output characteristics are the output stiffness, defined as the change in force output for a unit change in joint angle at a constant level of stimulation, and the length dependency mean-squared error. Recruitment gain was found to be of secondary influence on the grasp output, and the threshold, force direction and non-linearity of the stimulus level to force relationship were found to have little influence on the grasp output. These results establish criteria for electrode selection and implantation for use in upper extremity FNS.

Electric Stimulation Therapy↗

PubMed1990

Electrode characterization for functional application to upper extremity FNS.

A quantitative method has been developed to characterize the isometric force vectors of electrically stimulated paralyzed muscles of the thumb. The vectorial force output as a function of the stimulus level was measured for individual electrode/muscle combinations in a number of intramuscular and epimysial electrodes implanted in paralyzed thenar muscles of cervical level spinal cord injury subejcts. Vectors are used to determine the output characteristics of each electrode/muscle combination. The characteristics studied include: the strength of the contraction, the stimulus level at which fibers from other muscles are stimulated, the recruitment gain of force, dependency of the output on the skeletal position, and the direction of force produced. These characteristics can then be used to select stimulus parameters to produce coordinated hand motion and force generation by functional neuromuscular stimulation (FNS). The range of muscle force and direction for each electrode/muscle combination showed considerable variation between subjects and between electrodes in the same subject. This variation is primarily due to differences in electrode placement within the muscle. Comparison between intramuscular and epimysial electrodes demonstrated similar characteristics in the force vector output. Preliminary results show the potential for using the force vector output to predict the cocontracted output of two muscles.

Electric Stimulation↗

PubMed1989

Implantable functional neuromuscular stimulation in the tetraplegic hand.

Functional neuromuscular stimulation of the upper extremity provides manipulative capacity to persons with high level tetraplegia who have insufficient voluntary muscles available for tendon transfer surgery. We report an enhancement of the technique to include surgical implantation of a multichannel receiver-stimulator, sensory feedback stimulation, and tendon transfers. Tendon transfers were done with spastic, rather than voluntary motors employing standard surgical techniques. The system described has been operational for more than 1 1/2 years.

Activities of Daily Living↗

PubMed1989

Synthesis of hand grasp using functional neuromuscular stimulation.

A functional neuromuscular stimulation system has been developed to provide grasp-release function in quadriplegic individuals. A single command input from the subject controls the stimulus levels to a number of electrodes, thus simultaneously activating several muscles. A method for synthesizing the command input to stimulus output relationship has been developed. The first step involves electrode profiling, which is a method for characterizing the output of an individual electrode/muscle combination. The electrodes are then grouped according to function and a set of rule based procedures is used to synthesize the basic grasp parameters. Results are presented demonstrating the output from lateral and palmar grasps developed by this method. The method has successfully resulted in grasping patterns that can be utilized functionally. Limitations of the method and future improvements are discussed.

Electric Stimulation Therapy↗

PubMedDate not supplied

Neuroprosthesis consumers' forum: consumer priorities for research directions.

The purpose of this forum was to discuss with consumers having spinal cord injury what their research priorities would be for the field of functional electrical stimulation (FES) and to explore the impact of technology in the lives of people with disabilities. Both FES users and nonusers were included on the panel. The format for the discussion was primarily question and answer, with each participant giving his or her personal response to the moderator's question. Consumer research priorities depended on the individual and his or her personal priorities, preferences, background, history, and level of injury. Common themes that emerged were independence, ease of movement, ease of control, and spontaneity. From the consumers' perspective, the focus of research to restore function ought to be based on the needs and desires of the consumer, not just on the scientifically intriguing aspects of a particular technology.

Electric Stimulation Therapy↗