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Biomedical subjects

Edelle C Field-Fote

Publications and source records attributed to Edelle C Field-Fote.

8 recordsLinked to original sources
PubMed2007

Cortical reorganization following bimanual training and somatosensory stimulation in cervical spinal cord injury: a case report.

BACKGROUND AND PURPOSE: Deficits in upper-extremity function in individuals with tetraplegia are primarily due to the loss of motor pathways. Detrimental cortical reorganization, however, may create further loss of function. The purpose of this case report is to describe the cortical changes associated with a combination intervention using bimanual massed practice training with somatosensory stimulation. CASE DESCRIPTION: "BR" was a 22-year-old man with C6 tetraplegia and hand impairment who participated in this training intervention for 3 weeks. OUTCOMES: BR demonstrated improvements in sensory function, strength (the force-generating capacity of muscle), and performance of functional hand skills. Following the training, the cortical motor map of the biceps brachii muscle shifted anteriorly and increased in area and volume. DISCUSSION: This is the first documented case in which changes in the size and location of the cortical map were associated with an intervention and improvement in function in an individual with tetraplegia. This case suggests that an intensive training intervention may induce both functional and neurophysiological changes.

Adult↗
PubMed2006

Influence of posture and stimulus parameters on post-activation depression of the soleus H-reflex in individuals with chronic spinal cord injury.

In non-disabled (ND) individuals, reflexes are modulated by influences related to physiologic state (e.g., posture, joint position, load) and activation history. Repeated activation of the H-reflex results in post-activation depression (PAD) of the response amplitude. The modulation associated with physiologic state and activation history is suppressed or abolished in individuals with spinal cord injury (SCI). While posture is known to affect H-reflex amplitude and PAD in non-disabled individuals, the effect of posture on PAD in SCI individuals is not known. Further, while the amount of PAD is also known to be influenced by the stimulus rate and by the amplitude of the evoked reflex, the interaction of posture with stimulus parameters has not been previously investigated in either group. We investigated differences in PAD of the soleus H-reflex between SCI subjects and ND subjects during sitting versus supported standing. Subjects were tested using paired conditioning-test stimulus pulses of 2.5s and 5s interpulse intervals (ISI) and with stimulus intensity adjusted to evoke reflex responses of 20% and 40% of the maximum motor response. We found standing posture to be associated with significantly less PAD in SCI subjects compared to ND subjects. In both groups, shorter ISIs and smaller reflex amplitudes were associated with greater PAD of the H-reflex. These results indicate that postural influences on post-activation modulation, while present, are impaired in individuals with chronic incomplete SCI.

Adolescent↗
PubMed2005

Locomotor training approaches for individuals with spinal cord injury: a preliminary report of walking-related outcomes.

BACKGROUND AND PURPOSE: Body weight supported (BWS) locomotor training improves overground walking ability in individuals with motor-incomplete spinal cord injury (SCI). While there are various approaches available for locomotor training, there is no consensus regarding which of these is optimal. The purpose of this ongoing investigation is to compare outcomes associated with these different training approaches. SUBJECTS AND METHODS: Twenty-seven subjects with chronic motor-incomplete SCI have completed training and initial and final testing at the time of this preliminary report. Subjects were randomly assigned to 1 of 4 different BWS assisted-stepping groups, including: (1) treadmill training with manual assistance (TM), (2) treadmill training with stimulation (TS), (3) overground training with stimulation (OG), or (4) treadmill training with robotic assistance (LR). Prior to and following participation we assessed walking-related outcome measures including overground walking speed, training speed, step length, and step symmetry. RESULTS: Data pooled across all subject groups showed a significant effect of training on walking speed. While the differences between groups were not statistically significant, there was a trend toward greater improvement in the TS and OG groups. Post hoc subgroup analysis of outcomes from subjects with slower initial walking speed (< 0.1 m/s; n = 15) compared to those with faster initial walking speeds (> or = 0.1 m/s; n = 12) identified meaningful differences in outcomes with walking speed increasing by 85% in the slower group and by only 9% in the faster group. Step length of both stronger and weaker limb increased in all groups with the exception of those in the LR group. Step symmetry was increased in the TM and LR groups. DISCUSSION AND CONCLUSION: These results represent preliminary findings of changes in walking-related function associated with different forms of BWS locomotor training for individuals with chronic, motor-incomplete SCI. Early data indicates that locomotor outcomes in these individuals appear to be comparable across training approaches. For the individuals in this study sample, those with the greatest deficits in walking function benefitted the most from locomotor training.

Adult↗
PubMed2005

Massed practice versus massed practice with stimulation: effects on upper extremity function and cortical plasticity in individuals with incomplete cervical spinal cord injury.

OBJECTIVE: To determine the effect of massed practice (MP) versus massed practice combined with somatosensory stimulation (MP+SS) on cortical plasticity and function in persons with incomplete tetraplegia. METHODS: Ten subjects were assigned to either MP or MP+SS. Median nerve stimulation (500 ms train, 10 Hz, 1 ms pulse duration) was delivered at the intensity eliciting a motor threshold response. Training sessions were 5 d/week for 3 weeks at 2 h/session. Outcome measures included 1) motor-evoked potentials (MEPs) elicited via transcranial magnetic stimulation (TMS), motor threshold (MT) and MEP amplitude at 1.2 MT; 2) maximal pinch grip force; 3) Wolf Motor Function Test (WMFT) and Jebsen Hand Function Test. RESULTS: The MP+SS group demonstrated significant improvements (P < 0.05) in pinch grip strength (190%), WMFT scores (52%), and Jebsen test scores (33%), whereas the MP group demonstrated significant improvement (P < 0.05) only in Jebsen test scores (11%). No significant changes were detected in cortical excitability in the MP+SS or MP group. CONCLUSIONS: The findings of this preliminary study suggest that MP+SS results in greater increases in pinch strength and timed functional test scores than MP. Optimal stimulation paradigms and training methods are needed to further test this strategy.

Aged↗
PubMed2003

Impaired posture-dependent modulation of disynaptic reciprocal Ia inhibition in individuals with incomplete spinal cord injury.

Posture influences the strength of spinal reflex circuits in healthy individuals. The purpose of this study was to determine the extent to which sitting and standing posture influences the strength of reciprocal Ia inhibition between ankle flexor and extensor muscles in individuals with incomplete spinal cord injury (SCI). Ten individuals with SCI and 15 healthy individuals participated in the study. Short-latency reciprocal inhibition was measured by conditioning the soleus H-reflex with stimulation of the common peroneal nerve. There was no significant difference in the strength of reciprocal Ia inhibition in sitting and standing positions in individuals with SCI. However, healthy individuals showed increased inhibition in a standing compared to a sitting position. The results suggest an impaired posture-dependent modulation of reciprocal Ia inhibition following SCI.

Adult↗
PubMed2003

Patterned sensory stimulation induces plasticity in reciprocal ia inhibition in humans.

Training of spinal cord circuits using sensorimotor stimulation has been proposed as a strategy to improve movement after spinal injury. How sensory stimulation may lead to long-lasting changes is not well understood. We studied whether sensory stimulation might induce changes in the strength of a specific spinal interneuronal circuit: spinally mediated reciprocal Ia inhibition. In healthy humans, the strength of reciprocal inhibition between ankle flexor and extensor muscles was assessed before and after 30 min of peroneal nerve stimulation at motor threshold intensity. Three stimulation protocols were assessed: patterned nerve stimulation (10 pulses at 100 Hz every 1.5 sec), uniform nerve stimulation (one pulse every 150 msec), and combined stimulation of the peroneal nerve and the motor cortex with transcranial magnetic stimulation. Short-latency reciprocal inhibition from ankle flexor to extensor muscles was measured by conditioning the soleus H-reflex with stimulation of the common peroneal nerve. The strength of the reciprocal inhibition was measured at baseline and for 20 min after each stimulation session. Patterned stimulation, with or without motor cortex stimulation, enhanced reciprocal inhibition for at least 5 min afterward. The uniform pattern of stimulation was ineffective. These results demonstrate the presence of short-term plasticity within spinal inhibitory circuits. We conclude that the pattern of sensory input is a crucial factor for inducing changes in the spinal circuit for reciprocal inhibition in humans. These findings may have implications for the use of repetitive patterned sensory stimulation in rehabilitative efforts to improve walking ability in patients with spinal injury.

Adult↗
PubMed2003

Monophasic and biphasic stimulation evoke different responses.

In 31 subjects, psychophysiological sensory perception threshold and the waveform of orthodromic sensory nerve action potentials (SNAPs) produced by constant-current 100-micros monophasic negative pulses were compared to those produced by biphasic (negative-positive) symmetrical pulses (100-micros per phase). In addition, the effects of 200-micros monophasic negative pulses were studied. Graded stimuli were delivered to the index finger, and SNAPs were recorded over the median nerve at the wrist. Perception threshold was significantly different among the three conditions. Furthermore, in 26 subjects, at the lower intensities at which SNAPs first appeared, the evoked potential waveform had two small negative phases with biphasic stimuli, but a single negative phase in response to monophasic pulses. At higher stimulus intensities, all SNAPs had a single large negative phase regardless of the stimulus. These perception and waveform findings suggest that, contrary to historical belief, the trailing positive phase of a biphasic pulse has a stimulating effect at low stimulus intensities.

Action Potentials↗