Barry McKay - Academia.edu (original) (raw)

Papers by Barry McKay

Neurorehabilitation and neural repair, Jan 18, 2015

The human lumbosacral spinal circuitry can generate rhythmic motor output in response to differen... more The human lumbosacral spinal circuitry can generate rhythmic motor output in response to different types of inputs after motor-complete spinal cord injury. To explore spinal rhythm generating mechanisms recruited by phasic step-related sensory feedback and tonic posterior root stimulation when provided alone or in combination. We studied stepping in 4 individuals with chronic, clinically complete spinal cord injury using a robotic-driven gait orthosis with body weight support over a treadmill. Electromyographic data were collected from thigh and lower leg muscles during stepping with 2 hip-movement conditions and 2 step frequencies, first without and then with tonic 30-Hz transcutaneous spinal cord stimulation (tSCS) over the lumbar posterior roots. Robotic-driven stepping alone generated rhythmic activity in a small number of muscles, mostly in hamstrings, coinciding with the stretch applied to the muscle, and in tibialis anterior as stance-phase synchronized clonus. Adding tonic 3...

American Journal of Neuroprotection and Neuroregeneration, 2016

Experimental Brain Research, 2021

Increased use of epidural Spinal Cord Stimulation (eSCS) for the rehabilitation of spinal cord in... more Increased use of epidural Spinal Cord Stimulation (eSCS) for the rehabilitation of spinal cord injury (SCI) has highlighted the need for a greater understanding of the properties of reflex circuits in the isolated spinal cord, particularly in response to repetitive stimulation. Here, we investigate the frequency-dependence of modulation of short- and long-latency EMG responses of lower limb muscles in patients with SCI at rest. Single stimuli could evoke short-latency responses as well as long-latency (likely polysynaptic) responses. The short-latency component was enhanced at low frequencies and declined at higher rates. In all muscles, the effects of eSCS were more complex if polysynaptic activity was elicited, making the motor output become an active process expressed either as suppression, tonic or rhythmical activity. The polysynaptic activity threshold is not constant and might vary with different stimulation frequencies, which speaks for its temporal dependency. Polysynaptic ...

American Journal of EEG Technology

Spinal cord, May 1, 2018

Cross-sectional survey. Determine the impact of motor control characteristics attributed to spast... more Cross-sectional survey. Determine the impact of motor control characteristics attributed to spasticity, such as spasms, stiffness, and clonus on the daily life of people with spinal cord injury (SCI). Nationwide, United States. Internet-administered questionnaire, the Patient Reported Impact of Spasticity Measure (PRISM) and items describing characteristics of spasticity including stiffness, spasms, clonus, and pain. Of the 145 respondents, 113 (78%) reported a PRISM score of at least 5/164, indicating spasticity had some impact on their daily lives. Stiffness impact was highly correlated (ρ = 0.84; p < 0.01) with the PRISM negative impact on Daily Activities subscale and moderately correlated with the other PRISM subscales (ρ = 0.55-0.63; p < 0.01). Spasm presence had a negligible or low correlation with PRISM negative impact subscales (ρ = 0.29-0.47; p < 0.01). Trunk muscle stiffness and spasms had a low correlation with PRISM Need for Assistance and Daily activities (ρ =...

Spinal cord, Jun 1, 2018

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2002

Ten subjects diagnosed with a spinal cord injury participated in gait training. Six patients were... more Ten subjects diagnosed with a spinal cord injury participated in gait training. Six patients were ASIA C and four were ASIA D. Nine were trained using supported treadmill ambulation training (STAT), while one was trained conventionally. Each was trained for twenty minutes, five days per week for three months. Before training, patient motor control patterns were evaluated bilaterally from five

Applied neurophysiology, 1980

The averaged electrical potentials evoked by the stimulation of the peripheral nerves were record... more The averaged electrical potentials evoked by the stimulation of the peripheral nerves were recorded with surface electrodes over the lumbosacral, lower thoracic and cervical spine and with epidurally placed electrodes in the cervical area. The waveforms of the lumbosacral and cervical spinal cord potentials show similar complexity reflecting peripheral and central generators. The larger negative wave with at least two components is followed by a slower positive deflection. Evoked potentials recorded over the cervical segments of the spinal cord with epidural electrodes are of much higher amplitude and more complex waveform than those recorded with surface electrodes.

Restorative neurology and neuroscience, 1993

The tonic stretch reflex elicited by vibration of a muscle or tendon provides a means of studying... more The tonic stretch reflex elicited by vibration of a muscle or tendon provides a means of studying segmental reflex activity in humans with impaired volitional motor activity due to spinal cord injury (SCI). Vibration applied to the achilles or patellar tendon in a group of 51 SCI subjects elicited motor unit activity different from that found in 12 healthy subjects. Four distinct features of motor unit responses to vibration of a single tendon (achilles or patellar) could be seen in the SCI subjects: (i) a rapid onset, tonic response, frequently beginning with a single burst analogous to a tendon jerk, in 72% of vibrated sites; (ii) repetitive, phasic bursts of activity or vibratory-induced clonus in 23% of the tonic responses; (iii) spread of activity to muscles distant from the vibration in 44% of the tonic responses; and vibratory-induced withdrawal reflexes (VWR) which occurred after vibration of 37% of the sites. Overall, 81% of stimulated sites responded to vibration in SCI su...

Advances in neurology, 1997

We have described motor control in people with different degrees of SCI by using surface polyelec... more We have described motor control in people with different degrees of SCI by using surface polyelectromyographic recordings during single- and multijoint volitional motor tasks. We have shown that neurobiologic conditions of the injured spinal cord can be expressed in two main categories: "new anatomy" and "reduced anatomy". The evidence for a variety of definite features of motor control elicited by volitional effort for the performance of a present or even clinically absent motor task suggests that we can benefit from animal experimental neurobiologic studies while we are progressing toward the application of this new knowledge for the restoration of impaired spinal cord function in humans. Reports on the successfully enhanced regenerating capabilities of the axons and improved connectivity within neuronal circuits after SCI encourage us to intensify our efforts in parallel with studies on the recovery processes found in experimentally induced lesions in animals,...

Respiratory physiology & neurobiology, 2014

This case-controlled clinical study was undertaken to investigate to what extent pulmonary functi... more This case-controlled clinical study was undertaken to investigate to what extent pulmonary function in individuals with chronic spinal cord injury (SCI) is affected by posture. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax) were obtained from 27 individuals with chronic motor-complete (n=13, complete group) and motor-incomplete (n=14, incomplete group) C2-T12 SCI in both seated and supine positions. Seated-to-supine changes in spirometrical (FVC and FEV1) and airway pressure (PImax and PEmax) outcome measures had different dynamics when compared in complete and incomplete groups. Patients with motor-complete SCI had tendency to increase spirometrical outcomes in supine position showing significant increase in FVC (p=.007), whereas patients in incomplete group exhibited decrease in these values with significant decreases in FEV1 (p=.002). At the same time, the airway pressure val...

Journal of Visualized Experiments, 2013

Electroencephalography and Clinical Neurophysiology, 1983

Wiley Encyclopedia of Biomedical Engineering, 2006

Respiratory Physiology & Neurobiology, 2013