Biomedical subjects

Romeo Chua

Publications and source records attributed to Romeo Chua.

39 records · Page 3Linked to original sources

PubMed1999

Goal-Directed Aiming: Correcting a Force-Specification Error With the Right and Left Hands.

In 2 experiments, the authors examined manual aiming asymmetries as well as the ability of participants to adjust their aiming trajectories following an unexpected change to the inertial resistance to movement. In Experiment 1, participants (N = 11) were able to rapidly adjust their movement trajectories to conform to the new movement requirements. They were faster and more consistent when aiming with their right hand than with their left hand, regardless of whether or not the movement was perturbed. In Experiment 2, participants' (N = 11) vision of the hand was manipulated so that the role of visual feedback in the corrective process could be examined. Vision had an impact not only on performance but also on the characteristics of the movement trajectories. Manual asymmetries in aiming were associated with a right hand superiority during the final corrective stages of the movement.

Journal Article↗

PubMedDate not supplied

Possible contributions of CPG activity to the control of rhythmic human arm movement.

There is extensive modulation of cutaneous and H-reflexes during rhythmic leg movement in humans. Mechanisms controlling reflex modulation (e.g., phase- and task-dependent modulation, and reflex reversal) during leg movements have been ascribed to the activity of spinal central pattern generating (CPG) networks and peripheral feedback. Our working hypothesis has been that neural mechanisms (i.e., CPGs) controlling rhythmic movement are conserved between the human lumbar and cervical spinal cord. Thus reflex modulation during rhythmic arm movement should be similar to that for rhythmic leg movement. This hypothesis has been tested by studying the regulation of reflexes in arm muscles during rhythmic arm cycling and treadmill walking. This paper reviews recent studies that have revealed that reflexes in arm muscles show modulation within the movement cycle (e.g., phase-dependency and reflex reversal) and between static and rhythmic motor tasks (e.g., task-dependency). It is concluded that reflexes are modulated similarly during rhythmic movement of the upper and lower limbs, suggesting similar motor control mechanisms. One notable exception to this pattern is a failure of contralateral arm movement to modulate reflex amplitude, which contrasts directly with observations from the leg. Overall, the data support the hypothesis that CPG activity contributes to the neural control of rhythmic arm movement.

Arm↗

PubMedDate not supplied

Vestibulospinal influences on lower limb motoneurons.

Galvanic vestibular stimulation (GVS) is a research tool used to activate the vestibular system in human subjects. When a low-intensity stimulus (1-4 mA) is delivered percutaneously to the vestibular nerve, a transient electromyographic response is observed a short time later in lower limb muscles. Typically, galvanically evoked responses are present when the test muscle is actively engaged in controlling standing balance. However, there is evidence to suggest that GVS may be able to modulate the activity of lower limb muscles when subjects are not in a free-standing situation. The purpose of this review is to examine 2 studies from our laboratory that examined the effects of GVS on the lower limb motoneuron pool. For instance, a monopolar monaural galvanic stimulus modified the amplitude of the ipsilateral soleus H-reflex. Furthermore, bipolar binaural GVS significantly altered the onset of activation and the initial firing frequency of gastrocnemius motor units. The following paper examines the effects of GVS on muscles that are not being used to maintain balance. We propose that GVS is modulating motor output by influencing the activity of presynaptic inhibitory mechanisms that act on the motoneuron pool.

H-Reflex↗