Effect of central lesions on a spinal circuit facilitating human wrist flexors.

A putative spinal circuit with convergent inputs facilitating human wrist flexors has been recently described. This study investigated how central nervous system lesions may affect this pathway. We measured the flexor carpi radialis H-reflex conditioned with stimulation above motor threshold to the extensor carpi radialis at different intervals in fifteen patients with stroke and nine with spinal cord injury.

Spasms after spinal cord injury show low-frequency intermuscular coherence.

Intermuscular coherence allows the investigation of common input to muscle groups. Although beta-band (15-30 Hz) intermuscular coherence is well understood as originating from the cortex, the source of intermuscular coherence at lower frequencies is still unclear. We used a wearable device that recorded electromyographic (EMG) signals during a 24-h period in four lower limb muscles of seven spinal cord injury patients (American Spinal Cord Injury Association impairment scale: A, 6 subjects; B, 1 subject) while they went about their normal daily life activities.

Descending Inputs to Spinal Circuits Facilitating and Inhibiting Human Wrist Flexors.

Recently we reported in humans that electrical stimulation of the wrist extensor muscle extensor carpi radialis (ECR) could facilitate or suppress the H reflex elicited in flexor carpi radialis (FCR), for inter-stimulus intervals (ISIs) of 30 ms or 70 ms, respectively. The facilitation at 30 ms may be produced by both flexor afferents and extensor Ib afferents acting on a spinal circuit; the origin of the suppression at 70 ms is less certain. In this study, we investigated possible descending inputs to these systems.

Convergent Spinal Circuits Facilitating Human Wrist Flexors.

Noninvasive assessment of spinal circuitry in humans is limited, especially for Ib pathways in the upper limb. We developed a protocol in which we evoke the H-reflex in flexor carpi radialis (FCR) by median nerve stimulation and condition it with electrical stimulation above motor threshold over the extensor carpi radialis (ECR) muscle belly. Eighteen healthy adults (8 male, 10 female) took part in the study.

Postural Control During Cascade Ball Juggling: Effects of Expertise and Base of Support.

Cascade ball juggling is a complex perceptual motor skill which requires efficient postural stabilization. The aim of this study was to investigate effects of experience (expert and intermediate groups) and foot distance (wide and narrow stances) on body sway of jugglers during three ball cascade juggling. A total of 10 expert jugglers and 11 intermediate jugglers participated in this study.

Effects of Shift Work on the Postural and Psychomotor Performance of Night Workers.

The purpose of the study was to investigate the effects of shift work on the psychomotor and postural performance of night workers. The study included 20 polysomnography technicians working schedule of 12-h night shift by 36-h off. On the first day of protocol, the body mass and height were measured, and an actigraph was placed on the wrist of each participant.

Adaptation of sensorimotor coupling in postural control is impaired by sleep deprivation.

The purpose of the study was to investigate the effects of sleep deprivation (SD) in adaptation of the coupling between visual information and body sway in young adults' postural control due to changes in optic flow characteristics. Fifteen young adults were kept awake for approximately 25 hours and formed the SD group, while fifteen adults who slept normally the night before the experiment participated as part of the control group. All participants stood as still as possible in a moving room before and after being exposed to one trial with higher amplitude and velocity of room movement.

Sleep deprivation affects sensorimotor coupling in postural control of young adults.

Although impairments in postural control have been reported due to sleep deprivation, the mechanisms underlying such performance decrements still need to be uncovered. The purpose of this study was to investigate the effects of sleep deprivation on the relationship between visual information and body sway in young adults' postural control. Thirty adults who remained awake during one night and 30 adults who slept normally the night before the experiment participated in this study.

Explicit and implicit knowledge of environment states induce adaptation in postural control.

The aim of this study was to investigate the effects of explicit and implicit knowledge about visual surrounding manipulation on postural responses. Twenty participants divided into two groups, implicit and explicit, remained in upright stance inside a "moving room". In the fourth trial participants in the explicit group were informed about the movement of the room while participants in the implicit group performed the trial with the room moving at a larger amplitude and higher velocity.