A. Prochazka - Academia.edu (original) (raw)

Papers by A. Prochazka

Research paper thumbnail of Proprioception during voluntary movement

Canadian Journal of Physiology and Pharmacology, 1986

In the last decade, a number of laboratories have accumulated data on the firing of single affere... more In the last decade, a number of laboratories have accumulated data on the firing of single afferent fibres from muscle and skin during movement in awake cats, monkeys and human subjects. While there is general agreement on the firing behaviour of skin afferents and tendon organ (Ib) afferents during movement, there remains a significant divergence of opinion regarding the way in which the response of muscle spindle afferents (Ia and II) to length changes is modified by fusimotor action (e.g., alpha–gamma linkage versus "fusimotor set"). The controversies surrounding the fusimotor system have tended to overshadow the emergence of several important characteristics of propioceptive behaviour, corroborated in separate laboratories, (i) Mean la firing rates during active movements are nearly always higher than at rest. Thus, activation of the fusimotor system is reserved for the control of, or preparation for, movement. In animals, there is now strong evidence that there is usu...

Research paper thumbnail of Characterization and optimization of the stimulus router system, a novel neuroprosthesis

Research paper thumbnail of Feedback Control of Movement

Encyclopedia of Neuroscience

Research paper thumbnail of International Spinal Cord Injury Data Sets

Research paper thumbnail of Responses of muscle spindles to stretch after a period of fusimotor activity compared in freely moving and anaesthetized cats

Neuroscience Letters, 1977

Research paper thumbnail of Transcutaneously Coupled, High-Frequency Electrical Stimulation of the Pudendal Nerve Blocks External Urethral Sphincter Contractions

Neurorehabilitation and Neural Repair, 2008

Background. Detrusor-sphincter dyssynergia is a condition in which reflexive contractions of the ... more Background. Detrusor-sphincter dyssynergia is a condition in which reflexive contractions of the external urethral sphincter occur during bladder contractions, preventing the expulsion of urine. High-frequency stimulation (kHz range) has been shown to elicit a fast-acting and reversible block of action potential propagation in peripheral nerves, which may be a useful technique in the management of this condition. Objective. The aim of these experiments was to see if a newly developed stimulus delivery system, capable of transmitting current transcutaneously to remote peripheral nerves using a passive implanted conductor, was an effective way to transmit high-frequency waveforms to the pudendal nerve to block ongoing sphincter contractions. Methods. High-frequency waveforms were delivered through the skin to the pudendal nerve using a passive implanted conductor in 6 adult cats anesthetized with isoflurane. Five of the experiments were acute, terminal procedures, and the remaining ca...

Research paper thumbnail of X-ray imaging of intramuscular markers during movement in man

Journal of Neuroscience Methods, 1986

Research paper thumbnail of Properties of the Stimulus Router System, a Novel Neural Prosthesis

IEEE Transactions on Biomedical Engineering, 2010

Research paper thumbnail of Biomechanical imperatives in the neural control of locomotion

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009

Research paper thumbnail of Properties of implanted electrodes for functional electrical stimulation

Annals of Biomedical Engineering, 1991

Research paper thumbnail of Attenuation of pathological tremors by functional electrical stimulation II: Clinical evaluation

Annals of Biomedical Engineering, 1992

Research paper thumbnail of Development of quantitative and sensitive assessments of physiological and functional outcome during recovery from spinal cord injury: A Clinical Initiative

Brain Research Bulletin, 2011

The ability to detect physiological changes associated with treatments to effect axonal regenerat... more The ability to detect physiological changes associated with treatments to effect axonal regeneration, or novel rehabilitation strategies, for spinal cord injury will be challenging using the widely employed American Spinal Injuries Association (ASIA) impairment scales (AIS) for sensory and motor function. Despite many revisions to the AIS standard neurological assessment, there remains a perceived need for more sensitive, quantitative and objective outcome measures. The purpose of Stage 1 of the Clinical Initiative was to develop these tools and then, in Stage 2 to test them for reliability against natural recovery and treatments expected to produce functional improvements in those with complete or incomplete spinal cord injury (SCI). Here we review aspects of the progress made by four teams involved in Stage 2. The strategies employed by the individual teams were (1) application of repetitive transcranial magnetic stimulation (rTMS) to the motor cortex in stable (chronic) SCI with intent to induce functional improvement of upper limb function, (2) a tele-rehabilitation approach using functional electrical stimulation to provide hand opening and grip allowing incomplete SCI subjects to deploy an instrumented manipulandum for hand and arm exercises and to play computer games, (3) weight-assisted treadmill walking therapy (WAT) comparing outcomes in acute and chronic groups of incomplete SCI patients receiving robotic assisted treadmill therapy, and (4) longitudinal monitoring of the natural progress of recovery in incomplete SCI subjects using motor tests for the lower extremity to investigate strength and coordination.

Research paper thumbnail of Limb movements generated by stimulating muscle, nerve and spinal cord

Archives italiennes de biologie, 2002

We have compared the movements generated by stimulation of muscle, nerve, spinal roots and spinal... more We have compared the movements generated by stimulation of muscle, nerve, spinal roots and spinal cord in anesthetized, decerebrate and spinalized cats. Each method produced a full range of movements of the cat's hind limb in the sagittal plane against a spring load, except for stimulation of the roots. Stimulation of the dorsal roots produced movements that were mainly up and forward, whereas stimulation of the ventral roots produced complementary movements (down and backward). Results from stimulation in the intermediate areas of the spinal cord were compared to predictions of the "movement primitives" hypothesis. We could not confirm that the directions were independent of stimulus amplitude or the state of descending inputs. Pros and cons of stimulating at some sites were provisionally considered for the reliable control of limb movements with functional electrical stimulation (FES) in clinical conditions.

Research paper thumbnail of General properties of locomotor control systems

Research paper thumbnail of The neuromechanical tuning hypothesis

Progress in Brain Research, 2007

Research paper thumbnail of Torque-angle relationships of human wrist muscles

Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1999

In intact human subjects we studied the relationship between active torque and angle about the wr... more In intact human subjects we studied the relationship between active torque and angle about the wrist using either surface electrical stimulation or voluntary effort to contract the muscles. The wrist was moved at a constant 10° s-1 by a torque motor from 50° flexion to 50° extension (full range-of-motion: ROM), or over 20° portions of this range. Isometric torque was

Research paper thumbnail of Neural prostheses

The Journal of Physiology, 2001

Research paper thumbnail of Coding of position by simultaneously recorded sensory neurones in the cat dorsal root ganglion

The Journal of Physiology, 2004

Research paper thumbnail of Control of Locomotor Cycle Durations

Journal of Neurophysiology, 2005

In intact animals and humans, increases in locomotor speed are usually associated with decreases ... more In intact animals and humans, increases in locomotor speed are usually associated with decreases in step cycle duration. Most data indicate that the locomotor central pattern generator (CPG) shortens cycle duration mainly by shortening the durations of extensor rather than flexor phases of the step cycle. Here we report that in fictive locomotion elicited by electrical stimulation of the midbrain locomotor region (MLR) in the cat, spontaneous variations in cycle duration were due more to changes in flexor rather than extensor phase durations in 22 of 31 experiments. The locomotor CPG is therefore not inherently extensor- or flexor-biased. We coined the term “dominant” to designate the phase (flexion or extension) showing the larger variation. In a simple half-center oscillator model, experimental phase duration plots were fitted well by adjusting two parameters that corresponded to background drive (“bias”) and sensitivity (“gain”) of the oscillator's timing elements. By analogy...

Research paper thumbnail of Sensory Control of Locomotion: Reflexes Versus Higher-Level Control

Advances in Experimental Medicine and Biology, 2002

Research paper thumbnail of Proprioception during voluntary movement

Canadian Journal of Physiology and Pharmacology, 1986

In the last decade, a number of laboratories have accumulated data on the firing of single affere... more In the last decade, a number of laboratories have accumulated data on the firing of single afferent fibres from muscle and skin during movement in awake cats, monkeys and human subjects. While there is general agreement on the firing behaviour of skin afferents and tendon organ (Ib) afferents during movement, there remains a significant divergence of opinion regarding the way in which the response of muscle spindle afferents (Ia and II) to length changes is modified by fusimotor action (e.g., alpha–gamma linkage versus "fusimotor set"). The controversies surrounding the fusimotor system have tended to overshadow the emergence of several important characteristics of propioceptive behaviour, corroborated in separate laboratories, (i) Mean la firing rates during active movements are nearly always higher than at rest. Thus, activation of the fusimotor system is reserved for the control of, or preparation for, movement. In animals, there is now strong evidence that there is usu...

Research paper thumbnail of Characterization and optimization of the stimulus router system, a novel neuroprosthesis

Research paper thumbnail of Feedback Control of Movement

Encyclopedia of Neuroscience

Research paper thumbnail of International Spinal Cord Injury Data Sets

Research paper thumbnail of Responses of muscle spindles to stretch after a period of fusimotor activity compared in freely moving and anaesthetized cats

Neuroscience Letters, 1977

Research paper thumbnail of Transcutaneously Coupled, High-Frequency Electrical Stimulation of the Pudendal Nerve Blocks External Urethral Sphincter Contractions

Neurorehabilitation and Neural Repair, 2008

Background. Detrusor-sphincter dyssynergia is a condition in which reflexive contractions of the ... more Background. Detrusor-sphincter dyssynergia is a condition in which reflexive contractions of the external urethral sphincter occur during bladder contractions, preventing the expulsion of urine. High-frequency stimulation (kHz range) has been shown to elicit a fast-acting and reversible block of action potential propagation in peripheral nerves, which may be a useful technique in the management of this condition. Objective. The aim of these experiments was to see if a newly developed stimulus delivery system, capable of transmitting current transcutaneously to remote peripheral nerves using a passive implanted conductor, was an effective way to transmit high-frequency waveforms to the pudendal nerve to block ongoing sphincter contractions. Methods. High-frequency waveforms were delivered through the skin to the pudendal nerve using a passive implanted conductor in 6 adult cats anesthetized with isoflurane. Five of the experiments were acute, terminal procedures, and the remaining ca...

Research paper thumbnail of X-ray imaging of intramuscular markers during movement in man

Journal of Neuroscience Methods, 1986

Research paper thumbnail of Properties of the Stimulus Router System, a Novel Neural Prosthesis

IEEE Transactions on Biomedical Engineering, 2010

Research paper thumbnail of Biomechanical imperatives in the neural control of locomotion

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009

Research paper thumbnail of Properties of implanted electrodes for functional electrical stimulation

Annals of Biomedical Engineering, 1991

Research paper thumbnail of Attenuation of pathological tremors by functional electrical stimulation II: Clinical evaluation

Annals of Biomedical Engineering, 1992

Research paper thumbnail of Development of quantitative and sensitive assessments of physiological and functional outcome during recovery from spinal cord injury: A Clinical Initiative

Brain Research Bulletin, 2011

The ability to detect physiological changes associated with treatments to effect axonal regenerat... more The ability to detect physiological changes associated with treatments to effect axonal regeneration, or novel rehabilitation strategies, for spinal cord injury will be challenging using the widely employed American Spinal Injuries Association (ASIA) impairment scales (AIS) for sensory and motor function. Despite many revisions to the AIS standard neurological assessment, there remains a perceived need for more sensitive, quantitative and objective outcome measures. The purpose of Stage 1 of the Clinical Initiative was to develop these tools and then, in Stage 2 to test them for reliability against natural recovery and treatments expected to produce functional improvements in those with complete or incomplete spinal cord injury (SCI). Here we review aspects of the progress made by four teams involved in Stage 2. The strategies employed by the individual teams were (1) application of repetitive transcranial magnetic stimulation (rTMS) to the motor cortex in stable (chronic) SCI with intent to induce functional improvement of upper limb function, (2) a tele-rehabilitation approach using functional electrical stimulation to provide hand opening and grip allowing incomplete SCI subjects to deploy an instrumented manipulandum for hand and arm exercises and to play computer games, (3) weight-assisted treadmill walking therapy (WAT) comparing outcomes in acute and chronic groups of incomplete SCI patients receiving robotic assisted treadmill therapy, and (4) longitudinal monitoring of the natural progress of recovery in incomplete SCI subjects using motor tests for the lower extremity to investigate strength and coordination.

Research paper thumbnail of Limb movements generated by stimulating muscle, nerve and spinal cord

Archives italiennes de biologie, 2002

We have compared the movements generated by stimulation of muscle, nerve, spinal roots and spinal... more We have compared the movements generated by stimulation of muscle, nerve, spinal roots and spinal cord in anesthetized, decerebrate and spinalized cats. Each method produced a full range of movements of the cat's hind limb in the sagittal plane against a spring load, except for stimulation of the roots. Stimulation of the dorsal roots produced movements that were mainly up and forward, whereas stimulation of the ventral roots produced complementary movements (down and backward). Results from stimulation in the intermediate areas of the spinal cord were compared to predictions of the "movement primitives" hypothesis. We could not confirm that the directions were independent of stimulus amplitude or the state of descending inputs. Pros and cons of stimulating at some sites were provisionally considered for the reliable control of limb movements with functional electrical stimulation (FES) in clinical conditions.

Research paper thumbnail of General properties of locomotor control systems

Research paper thumbnail of The neuromechanical tuning hypothesis

Progress in Brain Research, 2007

Research paper thumbnail of Torque-angle relationships of human wrist muscles

Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1999

In intact human subjects we studied the relationship between active torque and angle about the wr... more In intact human subjects we studied the relationship between active torque and angle about the wrist using either surface electrical stimulation or voluntary effort to contract the muscles. The wrist was moved at a constant 10° s-1 by a torque motor from 50° flexion to 50° extension (full range-of-motion: ROM), or over 20° portions of this range. Isometric torque was

Research paper thumbnail of Neural prostheses

The Journal of Physiology, 2001

Research paper thumbnail of Coding of position by simultaneously recorded sensory neurones in the cat dorsal root ganglion

The Journal of Physiology, 2004

Research paper thumbnail of Control of Locomotor Cycle Durations

Journal of Neurophysiology, 2005

In intact animals and humans, increases in locomotor speed are usually associated with decreases ... more In intact animals and humans, increases in locomotor speed are usually associated with decreases in step cycle duration. Most data indicate that the locomotor central pattern generator (CPG) shortens cycle duration mainly by shortening the durations of extensor rather than flexor phases of the step cycle. Here we report that in fictive locomotion elicited by electrical stimulation of the midbrain locomotor region (MLR) in the cat, spontaneous variations in cycle duration were due more to changes in flexor rather than extensor phase durations in 22 of 31 experiments. The locomotor CPG is therefore not inherently extensor- or flexor-biased. We coined the term “dominant” to designate the phase (flexion or extension) showing the larger variation. In a simple half-center oscillator model, experimental phase duration plots were fitted well by adjusting two parameters that corresponded to background drive (“bias”) and sensitivity (“gain”) of the oscillator's timing elements. By analogy...

Research paper thumbnail of Sensory Control of Locomotion: Reflexes Versus Higher-Level Control

Advances in Experimental Medicine and Biology, 2002