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Michael Grey

University of Birmingham, School of Sport, Exercise and Rehabilitation Sciences, Faculty Member

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Dr Michael J Grey is a motor neuroscience physiologist with interests in cortical/spinal plasticity and neurorehabilitation. He uses non-invasive electrophysiology, transcranial magnetic stimulation and neuroimaging techniques to study human movement. He has a particular interest in acquired brain injury including stroke and concussion.
Phone: +44 (0) 121 414 7242

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Papers by Michael Grey

An Extensive Evaluation of Different Knee Stability Assessment Measures: A Systematic Review

Journal of Functional Morphology and Kinesiology, 2016

Viscoelastic properties of the human wrist during the stabilization phase of a targeted movement

Joint stability is a critical factor in the control of human movement. An understanding of the me... more

Resting state brain metabolism and functional connectivity of the occipital cortex in congenital blindness: a combined rTMS and PET-FDG study

NeuroImage, 2009

645 F-AM Source-localized EEG reveals neural basis of surround-suppression in human V1 and hMT+,

Functional electrical stimulation � the role of proprioceptive feedback

Neuroimage, 2009

Is muscle afferent contribution to the soleus muscle activity decreased during human spastic walking?

Proceedings of the Physiological Society, 2006

Rehabilitation of the hemiparetic gait supported by two modalities of electrical stimulation

Neurorehabilitation of hemiplegia using Functional Electrical Therapy

Afferent-Mediated Locomotor Activity

The objective of the present study was to investigate the involvement of afferent feedback in the... more The objective of the present study was to investigate the involvement of afferent feedback in the generation of plantar flexor muscle activity during human walking. Healthy subjects walked on a treadmill with the left leg attached to a portable stretching device. Changes in the soleus (SOL) background EMG were analyzed following slow, small amplitude, dorsiflexion perturbations applied to the ankle joint during the stance phase. The perturbations were applied with a small velocity increment compared with the ongoing ankle velocity (between 1 and 15 ˚/s). The results showed that the SOL muscle activity increased with the perturbation amplitude. It is argued that the observed change in the SOL background EMG could be due to the increased afferent feedback from muscle receptors in the stretched muscles.

Functional Electrical Therapy of Walking: Pilot Study

ABSTRACT

Group Ib afferents probably contribute to the human stance phase soleus EMG

Changes in cortical activity after a single training session with FET assessed by fMRI

Increased cortical excitability following one session of FET

Furthermore, FET might enhance motor recovery following stroke by increasing cortical excitabilit... more

Loss of Ground Support Produces a Decrement in SOL EMG during Human Walking

... Bibtex EndNote TEI RefWorks %% lirmm-00106446, version 1 %% http://hal-lirmm.ccsd.cnrs. fr/li... more

The TMS Map Scales with Increased Stimulation Intensity and Muscle Activation

Brain Topography, 2015

One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic st... more One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic stimulation (TMS) to construct a map of corticospinal excitability. TMS maps are reported to be acquired with a wide variety of stimulation intensities and levels of muscle activation. Whilst MEPs are known to increase both with stimulation intensity and muscle activation, it remains to be established what the effect of these factors is on the map's centre of gravity (COG), area, volume and shape. Therefore, the objective of this study was to systematically examine the effect of stimulation intensity and muscle activation on these four key map outcome measures. In a first experiment, maps were acquired with a stimulation intensity of 110, 120 and 130 % of resting threshold. In a second experiment, maps were acquired at rest and at 5, 10, 20 and 40 % of maximum voluntary contraction. Map area and map volume increased with both stimulation intensity (P \ 0.01) and muscle activation (P \ 0.01). Neither the COG nor the map shape changed with either stimulation intensity or muscle activation (P [ 0.09 in all cases). This result indicates the map simply scales with stimulation intensity and muscle activation.

the human soleus muscle Effects of prolonged walking on neural and mechanical components of stretch responses in

by Michael Grey and Masaki Ishikawa

Cronin NJ, Peltonen P, Ishikawa M, Komi PV, Avela J, Sinkjaer T, Voigt M. Effects of contraction ... more Cronin NJ, Peltonen P, Ishikawa M, Komi PV, Avela J, Sinkjaer T, Voigt M. Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae. The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8°; 250°/s) were applied to the triceps surae at different moment levels (0 -100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because shortlatency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required. stretch distribution; muscle spindle; short-latency reflex; ultrasound Address for reprint requests and other correspondence: N. J.

Barefoot vs Common Footwear: A systematic review of the kinematic, kinetic and muscle activity differences during walking

by Nicola Heneghan and Michael Grey

Gait & Posture, 2015

Hand grasp mirror training does not increase corticospinal excitability in all healthy participants

Brain Stimulation, 2015

TMS Brain Mapping in Less Than Two Minutes

Brain Stimulation, 2015

Transcranial magnetic stimulation (TMS) corticospinal excitability maps are a valuable tool to st... more Transcranial magnetic stimulation (TMS) corticospinal excitability maps are a valuable tool to study plasticity in the corticospinal tract. Traditionally, data acquisition for a single map is time consuming, limiting the method&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s applicability when excitability changes quickly, such as during motor learning, and in clinical investigations where assessment time is a limiting factor. To reduce the time needed to create a reliable map by 1) investigating the minimum interstimulus interval (ISI) at which stimuli may be delivered, and 2) investigating the minimum number of stimuli required to create a map. Frameless stereotaxy was used to monitor coil position as the coil was moved pseudorandomly within a 6 × 6 cm square. Maps were acquired using 1-4 s ISIs in 12 participants. The minimum number of stimuli was determined by randomly extracting data and comparing the resulting map to the original data set. To confirm validity, the pseudorandom walk method was compared against a traditional mapping method. Reliable maps could be created with 63 stimuli recorded with a 1 s ISI. Maps created acquiring data using the pseudorandom walk method were not significantly different from maps acquired following the traditional method. To account for inter-participant variability, outliers, coil positioning errors and, most importantly, participant comfort during data acquisition, we recommend creating a map with 80 stimuli and a 1.5 s ISI. This makes it possible to acquire TMS maps in 2 min, making mapping a more feasible tool to study short- and long-term changes in cortical organization.

Muscle Afferent Feedback during Human Walking

by Michel Ladouceur and Michael Grey

Frontiers in Neuroscience, 2001

TMS assessed cortical representation scales with stimulation intensity and muscle activation

Brain Stimulation, 2015

ABSTRACT Transcranial magnetic stimulation (TMS) is routinely used to construct a map of corticos... more ABSTRACT Transcranial magnetic stimulation (TMS) is routinely used to construct a map of corticospinal excitability (CSE). TMS elicited motor evoked potentials (MEPs) are known to increase both with stimulation intensity and muscle activation. Whilst a wide variety of stimulation intensities and levels of muscle activation are used to generate TMS maps, their effect on the cortical representation has yet to be systematically explored. Two experiments were performed to describe the effect of stimulation intensities (Experiment 1) and muscle activation (Experiment 2) on the map outcome measures: aspect ratio, centre of gravity (COG), map area and map volume. Twelve participants were recruited for each experiment. TMS maps were acquired from the first dorsal interosseous (FDI). Maps were acquired using 80 stimuli pseudorandomly across a 6x6 cm area with a 1.5 s interstimulus interval, allowing the maps to be acquired in two minutes. In Experiment 1 maps were compared at 5, 10, 20 and 40% of the maximum voluntary contraction. All maps were acquired with a stimulation intensity of 120% of the resting motor threshold (RMT). In Experiment 2 maps were compared at the stimulation intensities of 110, 120 and 130% of RMT, whilst the muscle was at rest. A significant increase in map area and map volume were observed with stimulation intensity and level of muscle activation as would be expected. Neither the COG nor the aspect ratio were changed with either increased stimulation intensity or muscle activation. This study demonstrates that the cortical representation scales with stimulation intensity and level of muscle activation, but the shape of the map does not change.

An Extensive Evaluation of Different Knee Stability Assessment Measures: A Systematic Review

Journal of Functional Morphology and Kinesiology, 2016

Viscoelastic properties of the human wrist during the stabilization phase of a targeted movement

Joint stability is a critical factor in the control of human movement. An understanding of the me... more

Resting state brain metabolism and functional connectivity of the occipital cortex in congenital blindness: a combined rTMS and PET-FDG study

NeuroImage, 2009

645 F-AM Source-localized EEG reveals neural basis of surround-suppression in human V1 and hMT+,

Functional electrical stimulation � the role of proprioceptive feedback

Neuroimage, 2009

Is muscle afferent contribution to the soleus muscle activity decreased during human spastic walking?

Proceedings of the Physiological Society, 2006

Rehabilitation of the hemiparetic gait supported by two modalities of electrical stimulation

Neurorehabilitation of hemiplegia using Functional Electrical Therapy

Afferent-Mediated Locomotor Activity

The objective of the present study was to investigate the involvement of afferent feedback in the... more The objective of the present study was to investigate the involvement of afferent feedback in the generation of plantar flexor muscle activity during human walking. Healthy subjects walked on a treadmill with the left leg attached to a portable stretching device. Changes in the soleus (SOL) background EMG were analyzed following slow, small amplitude, dorsiflexion perturbations applied to the ankle joint during the stance phase. The perturbations were applied with a small velocity increment compared with the ongoing ankle velocity (between 1 and 15 ˚/s). The results showed that the SOL muscle activity increased with the perturbation amplitude. It is argued that the observed change in the SOL background EMG could be due to the increased afferent feedback from muscle receptors in the stretched muscles.

Functional Electrical Therapy of Walking: Pilot Study

ABSTRACT

Group Ib afferents probably contribute to the human stance phase soleus EMG

Changes in cortical activity after a single training session with FET assessed by fMRI

Increased cortical excitability following one session of FET

Furthermore, FET might enhance motor recovery following stroke by increasing cortical excitabilit... more

Loss of Ground Support Produces a Decrement in SOL EMG during Human Walking

... Bibtex EndNote TEI RefWorks %% lirmm-00106446, version 1 %% http://hal-lirmm.ccsd.cnrs. fr/li... more

The TMS Map Scales with Increased Stimulation Intensity and Muscle Activation

Brain Topography, 2015

One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic st... more One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic stimulation (TMS) to construct a map of corticospinal excitability. TMS maps are reported to be acquired with a wide variety of stimulation intensities and levels of muscle activation. Whilst MEPs are known to increase both with stimulation intensity and muscle activation, it remains to be established what the effect of these factors is on the map's centre of gravity (COG), area, volume and shape. Therefore, the objective of this study was to systematically examine the effect of stimulation intensity and muscle activation on these four key map outcome measures. In a first experiment, maps were acquired with a stimulation intensity of 110, 120 and 130 % of resting threshold. In a second experiment, maps were acquired at rest and at 5, 10, 20 and 40 % of maximum voluntary contraction. Map area and map volume increased with both stimulation intensity (P \ 0.01) and muscle activation (P \ 0.01). Neither the COG nor the map shape changed with either stimulation intensity or muscle activation (P [ 0.09 in all cases). This result indicates the map simply scales with stimulation intensity and muscle activation.

the human soleus muscle Effects of prolonged walking on neural and mechanical components of stretch responses in

by Michael Grey and Masaki Ishikawa

Cronin NJ, Peltonen P, Ishikawa M, Komi PV, Avela J, Sinkjaer T, Voigt M. Effects of contraction ... more Cronin NJ, Peltonen P, Ishikawa M, Komi PV, Avela J, Sinkjaer T, Voigt M. Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae. The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8°; 250°/s) were applied to the triceps surae at different moment levels (0 -100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because shortlatency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required. stretch distribution; muscle spindle; short-latency reflex; ultrasound Address for reprint requests and other correspondence: N. J.

Barefoot vs Common Footwear: A systematic review of the kinematic, kinetic and muscle activity differences during walking

by Nicola Heneghan and Michael Grey

Gait & Posture, 2015

Hand grasp mirror training does not increase corticospinal excitability in all healthy participants

Brain Stimulation, 2015

TMS Brain Mapping in Less Than Two Minutes

Brain Stimulation, 2015

Transcranial magnetic stimulation (TMS) corticospinal excitability maps are a valuable tool to st... more Transcranial magnetic stimulation (TMS) corticospinal excitability maps are a valuable tool to study plasticity in the corticospinal tract. Traditionally, data acquisition for a single map is time consuming, limiting the method&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s applicability when excitability changes quickly, such as during motor learning, and in clinical investigations where assessment time is a limiting factor. To reduce the time needed to create a reliable map by 1) investigating the minimum interstimulus interval (ISI) at which stimuli may be delivered, and 2) investigating the minimum number of stimuli required to create a map. Frameless stereotaxy was used to monitor coil position as the coil was moved pseudorandomly within a 6 × 6 cm square. Maps were acquired using 1-4 s ISIs in 12 participants. The minimum number of stimuli was determined by randomly extracting data and comparing the resulting map to the original data set. To confirm validity, the pseudorandom walk method was compared against a traditional mapping method. Reliable maps could be created with 63 stimuli recorded with a 1 s ISI. Maps created acquiring data using the pseudorandom walk method were not significantly different from maps acquired following the traditional method. To account for inter-participant variability, outliers, coil positioning errors and, most importantly, participant comfort during data acquisition, we recommend creating a map with 80 stimuli and a 1.5 s ISI. This makes it possible to acquire TMS maps in 2 min, making mapping a more feasible tool to study short- and long-term changes in cortical organization.

Muscle Afferent Feedback during Human Walking

by Michel Ladouceur and Michael Grey

Frontiers in Neuroscience, 2001

TMS assessed cortical representation scales with stimulation intensity and muscle activation

Brain Stimulation, 2015

ABSTRACT Transcranial magnetic stimulation (TMS) is routinely used to construct a map of corticos... more ABSTRACT Transcranial magnetic stimulation (TMS) is routinely used to construct a map of corticospinal excitability (CSE). TMS elicited motor evoked potentials (MEPs) are known to increase both with stimulation intensity and muscle activation. Whilst a wide variety of stimulation intensities and levels of muscle activation are used to generate TMS maps, their effect on the cortical representation has yet to be systematically explored. Two experiments were performed to describe the effect of stimulation intensities (Experiment 1) and muscle activation (Experiment 2) on the map outcome measures: aspect ratio, centre of gravity (COG), map area and map volume. Twelve participants were recruited for each experiment. TMS maps were acquired from the first dorsal interosseous (FDI). Maps were acquired using 80 stimuli pseudorandomly across a 6x6 cm area with a 1.5 s interstimulus interval, allowing the maps to be acquired in two minutes. In Experiment 1 maps were compared at 5, 10, 20 and 40% of the maximum voluntary contraction. All maps were acquired with a stimulation intensity of 120% of the resting motor threshold (RMT). In Experiment 2 maps were compared at the stimulation intensities of 110, 120 and 130% of RMT, whilst the muscle was at rest. A significant increase in map area and map volume were observed with stimulation intensity and level of muscle activation as would be expected. Neither the COG nor the aspect ratio were changed with either increased stimulation intensity or muscle activation. This study demonstrates that the cortical representation scales with stimulation intensity and level of muscle activation, but the shape of the map does not change.