ORCID Profile
0000-0002-9323-1961
Current Organisation
Sydney Children's Hospital Randwick
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Springer Singapore
Date: 2022
Publisher: Wiley
Date: 10-1993
DOI: 10.1111/J.1476-5381.1993.TB13857.X
Abstract: 1. The effect of nitric oxide on the efficacy of synaptic transmission in the chick ciliary ganglion of post-hatched birds has been determined by use of the size of the postganglionic compound action potential resulting from chemical transmission through the ganglion as a measure of synaptic efficacy. 2. Sodium nitroprusside (100 microM) increased the synaptic efficacy by an average 26%. This is likely to be due to its ability to release nitric oxide, as potassium ferricyanide (100 microM) did not cause a potentiation. Sodium azide (100 microM), shown in sympathetic ganglia to stimulate production of cyclic GMP, did not modulate synaptic efficacy significantly. 3. 8-Br-cyclic-GMP (100 microM) increased synaptic efficacy by an average 61%. The addition of 8-Br-cyclic-AMP (100 microM) had less effect, increasing transmission by on average 46%. 4. The nitric oxide synthase blocker, NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) was added prior to the tetanic stimulation of the preganglionic nerves at 30 Hz for 20 s, a procedure known to produce both post-tetanic potentiation and long-term potentiation of synaptic transmission through the ganglion. L-NAME reduced the long-term potentiation by an average of 47% but did not significantly change the post-tetanic potentiation. 5. Following the brief application of 8-Br-cyclic AMP, 8-Br-cyclic GMP and sodium nitroprusside there was an enhancement of the efficacy of synaptic transmission that persisted after the withdrawal of the drugs. The maximum increase in synaptic efficacy following the brief addition of 8-Br-cyclic GMP was 116%, sodium nitroprusside was 110% and 8-Br-cyclic AMP was 126%.6. These results suggest that nitric oxide modulates synaptic transmission through the ganglion by acting on an endogenous guanylate cyclase that produces cyclic GMP.
Publisher: Wiley
Date: 09-1993
DOI: 10.1111/J.1476-5381.1993.TB13833.X
Abstract: 1. The effects of tetanic stimulation of the oculomotor nerve on transmission through the avian ciliary ganglion have been determined by use of the litude of the compound action potential recorded in the ciliary nerve, in the presence of hexamethonium (300 microM), as a measure of synaptic efficacy. 2. Tetanic stimulation for 20 s at 30 Hz potentiated the chemical phase of the compound action potential by at least 100% of its control level. This potentiation, reflecting an increase in synaptic efficacy, decayed over two distinct time courses: firstly, a rapid decay with a time constant in the order of minutes, and secondly, a slower decay, representing a smaller potentiation, with a time constant in the order of an hour. The large increase in synaptic efficacy is attributed to post-tetanic potentiation (PTP) whereas the smaller but longer lasting increase is attributed to long-term potentiation (LTP). 3. Higher frequencies of tetanic stimulation gave increased PTP and LTP. 4. In order to test whether the influx of calcium ions into the nerve terminal during the tetanus is likely to be involved in potentiation, facilitation was measured during PTP and LTP. Facilitation was reduced to approximately zero during PTP but recovered to normal values about 15 min into LTP. A requirement for the induction of LTP was shown to be the presence of calcium in the bathing solution. However, blocking synaptic transmission with a high concentration of hexamethonium (3 mM) during the tetanic stimulation did not block the induction of LTP. 5. Application of the muscarinic inhibitor, atropine (2 microM), did not affect the magnitude of PTP or LTP. 5. Application of the muscarinic inhibitor, atropine (2 tM), did not affect the magnitude of PTP or LTP.6. The activator of protein kinase C, phorbol 12,13-dibutyrate (2 microM) potentiated synaptic transmission and reduced the potentiation due to PTP although it did not affect that due to LTP, but the inhibitor of this kinase, staurosporine (0.5 microM), partially blocked the appearance of LTP without affecting PTP after the tetanus.7. An inhibitor of calmodulin, W-7 (5 microM), reversibly blocked the appearance of LTP significantly after a tetanus although the size of PTP was not affected.8. The results presented here suggest that the initiation of LTP in the ciliary ganglion is due to an influx of calcium ions into the calyciform nerve terminal during the tetanus and that the mechanism for LTP involves a calcium-calmodulin-dependent process.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-1997
DOI: 10.1109/86.593303
Abstract: The use of a probe measuring tendon tension for the purpose of controlling a neuroprosthesis suited to spinal cord injured persons is investigated. The implanted probe detected inwardly directed radial force exerted by the tendon as the result of longitudinal tension. Varying types of load were applied to the tendon in order to measure static and dynamic parameters of the probe within the tendon. The results are discussed with respect to the potential use of the probe, within an active muscle's tendon, as a hand grasp neuroprosthesis controller. In addition, use of the probe to monitor electrically stimulated paralyzed muscle for the augmentation of closed loop control schemes is discussed.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2000
DOI: 10.1109/86.867870
Abstract: 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.
Publisher: Elsevier BV
Date: 10-2001
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2001
DOI: 10.1109/7333.948453
Abstract: 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.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2000
DOI: 10.1109/86.867885
Abstract: 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.
Publisher: Springer Science and Business Media LLC
Date: 06-03-2015
DOI: 10.1007/S11517-015-1255-1
Abstract: Sensitivity analysis for a user command controller monitoring head position for artificial control of the proximal upper limb was performed. The controller was evaluated by having subjects complete target matching tasks manipulating a simulated on-screen hand representation to investigate the effects of target location and target speed on performance. Sixteen subjects took part in the study, 11 of whom had sustained cervical spinal cord injuries. The subjects were able to control the on-screen hand with overall low sensitivity of performance with the controller to target position in its five-degrees-of-freedom. The optimal speed was found to be a compromise between low speed and high accuracy but longer completion time and fast speed for short completion time with lower accuracy. The results demonstrated the robustness of the controller across a population of non-injured subjects and those with tetraplegia.
Publisher: SPIE
Date: 28-07-2003
DOI: 10.1117/12.484375
Publisher: Springer Science and Business Media LLC
Date: 13-12-2012
DOI: 10.1007/S11517-012-0996-3
Abstract: An independent lifestyle requires the ability to place the hand in the complete workspace in concert with hand grasp and release. A novel user command controller monitoring head position for purpose of controlling hand location and orientation is proposed and demonstrated. The controller detected five degrees of freedom which were applied to upper limb movements including forearm and hand placement in three-dimensional space. The controller was evaluated by having subjects complete tracking tasks manipulating a simulated on-screen upper limb representation. Thirteen of the eighteen subjects assessed using the controller had sustained a spinal cord injury at or above the sixth cervical vertebra. Two of the injured subjects with decreased cervical spine mobility were unable to operate the controller. The remaining subjects performed the tracking tasks effectively after minimal training. This simple five-degree of freedom controller has been proposed for the use by those disabled by upper limb utation, paralysis, weakness or hypertonicity.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-1996
DOI: 10.1109/86.547925
Abstract: 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.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 30-09-2019
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2000
DOI: 10.1109/86.847827
Abstract: 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.
Publisher: Springer Science and Business Media LLC
Date: 09-2002
DOI: 10.1007/BF02345459
Start Date: 2003
End Date: 2004
Funder: National Health and Medical Research Council
View Funded Activity