Synergistic control of stimulated pronosupination with the stimulated grasp of persons with tetraplegia.

The control of stimulated forearm pronosupination in concert with stimulated hand grasp of persons with tetraplegia has been investigated. It has been shown that hand grasp stability increased as supination was achieved. In accordance with this, a strategy of object acquisition has been proposed incorporating pronosupination and hand grasp. It has been proposed that, after object acquisition in the pronated posture, that supination be used to increase grasp stability. Three types of pronosupination control which act in synchrony with grasp were implemented incorporating this principle. The three types used were position-controlled pronator stimulation, touch-controlled pronator stimulation, and constant pronation stimulation. These controllers played a supporting role to the separate user control of hand grasp and release. The three controllers were evaluated and compared using a standardized test procedure that incorporated stimulated pronosupination control with stimulated grasp. Such methods of pronosupination control are likely to provide enhanced options for improving upper extremity function using electrical stimulation.

Detection of fatigue in the isometric electrical activation of paralyzed hand muscles of persons with tetraplegia.

Paralyzed muscle fatigue is the eventual depression of force due to either prolonged or repetitive electrical stimulation of motor units. The robustness and safety of future functional electrical stimulation (FES) systems will rely on their ability to detect the onset of muscle fatigue. The relative degree of muscle activation can be estimated by monitoring the M-wave. The aim of this study was to test a proposed method of quantitative fatigue assessment that detects muscle force output and its corresponding M-wave measured concurrently. The detection of force and M-wave concurrently allows any reduction in muscle force output to be attributed to either changes in the fatigue state of the stimulated muscle or changes in the degree of stimulus activation of that muscle. The fatigue assessment scheme can thereby accommodate the corresponding changes in muscle force caused by an alteration in the stimulation intensity during fatigue. The Extensor Digitorum Communis (EDC), Extensor Pollicis Longus (EPL), and Flexor Pollicis Longus (FPL) muscles of two C5/C6 tetraplegic men were studied. Stimulation recruitment tests over the pulsewidth range from 0 to 200 micros, were performed at intervals during 20 min of maximal stimulation (200 micro/s). Muscle force correlated to the M-wave parameter, second phase area, with mean correlation coefficients of greater than 0.82, when the muscle was in either a nonfatigued or fatiguing state. After the initial force, likely to be primarily due to the fast glycolytic (FG) motor units, had declined the M-wave demonstrated only minor changes throughout the fatigue of muscle force during 20 min of constant maximal stimulation. The second phase area and root-mean-square (rms) of the M-wave [see Fig. 2(a) reflected muscle activation during modulated stimulation and also remained relatively constant during the fatigue-related force decline when the muscle was stimulated at a constant intensity. This detection of M-wave parameters satisfies the defined requirement for a myoelectric parameter that indicates electrical activation, but is relatively invariant to muscular fatigue. Index Terms-Electrical stimulation, electromyography (EMG), functional electrical stimulation (FES), muscle fatigue, spinal cord injury, tetraplegia.

The use of bilateral stimulated hand grasp in the bimanual activities of persons with tetraplegia.

Grasp and release has been provided to both upper extremities of subjects with tetraplegia using percutaneous and fully implanted stimulation. This is to determine quantitatively the performance of these subjects in three bimanual tests using two handed stimulation. Their performance here is compared with two separate cases: the same tests using single handed stimulation assisted by a nonstimulated hand and using two unstimulated hands. It was found that bilateral stimulation significantly improved the efficacy of performing the bimanual tests assessed over that using unilateral stimulation assisted by the nonstimulated hand (in two of three tests) or no stimulation three of three tests). These results show quantitative evidence of the benefits of providing bilateral stimulation for the completion of bimanual tasks for persons with tetraplegia who are appropriate candidates for stimulated grasp. These benefits were observed especially in cases where the ability of the subject in completing the task using unilateral stimulation was not strong.

Quantitative evaluation of two methods of control of bilateral stimulated hand grasps in persons with tetraplegia.

Electrical stimulation has been applied to the paralyzed muscles of both hands of two persons with tetraplegia using percutaneous and implantable electrodes. Two separate methods of user control were being investigated. The first monitored the myoelectric signals from the user's own sternocleidomastoid muscles and the second monitored wrist joint angle. These signals were used as commands to modify the stimulated grasps. The hands were instrumented to detect the degree of hand closure and grip force and the users matched these to specific target parameters using the controller during tracking tasks. Performance in these tracking tasks was measured quantitatively. Wrist control was found to be less sensitive to the direction of hand opening/closing required than the myoelectric control. The user's performance with the myoelectric control demonstrated sensitivity to the target size and the speed of hand movement in response to the command control. The wrist controller required less training than the myoelectric controller for users to become proficient in its use. Based on these results, the wrist controller and the myoelectric controller both provide successful control of bilateral hand grasp and release. Of the two controllers, the wrist controller is likely to provide the greater ease of use, although it is only available to the population of users with active wrist extension.

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.

Colonic necrosis following sodium polystyrene sulfonate (Kayexalate)-sorbitol enema in a renal transplant patient. Report of a case and review of the literature.

The authors present the case of a patient who developed near total colonic necrosis shortly after renal transplantation. The onset of symptoms was temporally related to the administration of sodium polystyrene (Kayexalate; Sanofi Winthrop Pharmaceuticals, New York, NY)-sorbitol enemas for treatment of hyperkalemia. Three similar cases have been reported in the literature. The presence of uremia and the use of sorbitol appear to be common denominators in the pathophysiology of this complication. It is suggested that Kayexalate-sorbitol enemas be avoided in renal transplant patients.

The responsiveness of neurones in the frontal opercular gustatory cortex of the macaque monkey is independent of hunger.

1. In order to determine whether the responsiveness of neurones in the primary gustatory cortex is influenced by hunger, the activity of neurones in the gustatory cortex in the frontal operculum was recorded while macaque monkeys (Macaca fascicularis) were fed to satiety. The responses of single neurones in the gustatory cortex to the prototypical taste stimuli glucose, NaCl, HCl and quinine hydrochloride, and to fruit juice, were measured before, while, and after the monkey was fed to satiety with glucose or fruit juice. 2. While behaviour turned from avid acceptance to active rejection upon repletion, the responsiveness of the neurones to the stimulus array, including the satiating solution, was unmodified. 3. It is concluded that in the gustatory cortex in the frontal operculum, neuronal responses to gustatory stimuli are not influenced by the normal transition from hunger to satiety. This is in contrast to the responses of a population of neurones recorded in the hypothalamus, which only occur to the taste of food when the monkey is hungry. Thus the neurones in the primary gustatory cortex are involved in a motivation-independent analysis of gustatory stimuli, whereas the hypothalamic neurones may be more closely related to the influence of motivational state on behavioural responsiveness to gustatory stimuli.

Satiety does not affect gustatory activity in the nucleus of the solitary tract of the alert monkey.

Feeding to satiety decreases the acceptability of the taste of food. In order to determine whether the responsiveness of gustatory neurons in the nucleus tractus solitarius (NTS) is influenced by hunger, neural activity in the NTS was analyzed while monkeys were fed to satiety. Gustatory neural activity to glucose, fruit juice, NaCl, HCl and quinine HCl was measured before, while and after the monkey was fed to satiety with glucose, fruit juice or sucrose. While behavior turned from avid acceptance to active rejection upon repletion, the responsiveness of NTS neurons to the stimulus array, including the satiating solution, was unmodified. It is concluded that at the first central synapse of the taste system of the primate, neural responsiveness is not influenced by the normal transition from hunger to satiety. This is in contrast to the responses of a population of neurons recorded in the hypothalamus, which only occur to the taste of food when the monkey is hungry. Thus, NTS gustatory activity appears to occur independently of normal hunger and satiety, whereas hypothalamic neuronal activity is more closely related to the influence of motivational state on behavioral responsiveness to gustatory stimuli.

The effects of forced molt treatment on blood biochemicals in hens.

A study was conducted to determine the effects of an environmentally induced force molt treatment on concentrations and daily variations of selected serum biochemicals during early molt. Laying hens were placed into two environmental control chambers. In one chamber, control (Con) laying hens were maintained on long photoperiods of 19 hr of light daily to maintain egg production. In the other chamber, early molt (EM) hens were exposed to short photoperiods of 6 hr of light daily to decrease egg production. After 2 weeks in the chambers, feed was withdrawn from EM hens for 2 days to initiate molt. Three days after feed was restored, hens from both groups were blood sampled every 2 hr for 2 days for selected serum biochemical analyses. Serum concentrations of calcium (Ca), inorganic phosphate (P), glutamic pyruvic transaminase (GPT), and albumin (Alb) were depressed in EM hens. Serum concentrations of alkaline phosphatase (Alk P), lactic acid dehydrogenase (LDH), glutamic oxaloacetic transaminase (GOT), glucose (Glu), cholesterol (Chol), and globulin (Glob) were elevated in EM hens. Daily temporal rhythms of Ca, Glu, total protein (TP), and Alb were found in both hen groups. These temporal changes were independent of force molt treatment. Serum GOT was positively correlated with nuclei free liver corticosteroids (LCS) and negatively associated with plasma corticosterone in Con hens. Serum GOT was positively correlated with nuclei free LCS in EM hens.