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Biomedical subjects

C E Lathan

Publications and source records attributed to C E Lathan.

12 recordsLinked to original sources
PubMed2001

The interaction of spatial ability and motor learning in the transfer of training from a simulator to a real task.

Virtual Reality (VR) based simulators have been used as a training tool in many settings, although very few studies examine transfer of training from simulators to a real world task, particularly for manipulation tasks. Simulators could play a key role as an enabling technology for manipulation tasks related to teleoperation, and medical procedure training. We investigated the relationship between motor tasks and participants' spatial abilities. This relationship was further examined with respect to learning in a simulator and to transfer of training from the simulator to the real world on a pick-and-place task. Spatial abilities were characterized using a battery of recognition and manipulation figural tests. Subjects with lower spatial abilities demonstrated significant positive transfer from a simulator based training task to a similar real world robotic operation task. Subjects with higher spatial skills did not respond as positively from training in a simulated environment.

Aptitude↗
PubMed1999

Aspects of human factors engineering in home telemedicine and telerehabilitation systems.

Human factors engineering and system design are critical elements in the newly developing field of telerehabilitation. Telerehabilitation is the remote delivery of rehabilitative services such as monitoring, training, and long-term care of persons with disabilities using telecommunications technology. This paper describes projects at the Rehabilitation Engineering Research Center (RERC) on Telerehabilitation in the context of three conceptual models: telecounseling and training, telemonitoring and assessment, and teletherapy. Issues pertaining to human factors engineering design are identified, and ongoing challenges are discussed.

Biomedical Engineering↗
PubMed1999

Heuristic evaluation of a web-based interface for internet telemedicine.

A low-cost usability engineering methodology (heuristic evaluation combined with small-scale expert assessment) is examined in the context of the design and development of a Web-based telemedicine system. Six experts - three human-computer interaction (HCI) experts and three medical-content experts - examined the Spacebridge to Russia Web site for usability. The HCI experts identified 52 interface problems using a set of ten usability criteria or heuristics; these problems ranged in severity from cosmetic to a major failure. The content experts completed a series of six simple tasks while describing their actions. The usage difficulties were related to the HCI problems identified and were primarily characterized by a mismatch of the designer model and the content expert model. This heuristic/usage methodology can provide an incremental benefit in a variety of other design activities. It is suggested herein that the combined heuristic/usage methodology should be included as a standard design component of dynamic telemedicine systems.

Ergonomics↗
PubMed1999

Memory processes and motor control in extreme environments.

Cognitive-performance and motor-performance activities in multi-task, high-workload environments were assessed during astronaut performance in space flight and in isolation. Data was collected in microgravity on the International Micro-gravity Laboratory (IML) space shuttle mission (STS-42), and the Canadian Astronaut Program Space Unit Life Simulation (CAPSULS) mission offered an ideal opportunity to collect data for individuals in extreme isolation to complement the space flight data using similar hardware, software, and experimental protocols. The mental workload and performance experiment (MWPE) was performed during the IML-1 space flight mission, and the memory processes and motor control (MEMO) experiment was performed during the CAPSULS isolation mission. In both experiments, short-term exhaustive memory and fine motor control associated with human-computer interaction was studied. Memory processes were assessed using a Sternberg-like exhaustive memory search containing 1, 2, 4, or 7 letters. Fine motor control was assessed using velocity-controlled (joystick) and position-controlled (trackball) computer input devices to acquire targets as displayed on a computer screen. Subjects repeated the tasks under two conditions that tested perceptual motor adaptation strategies: 1) During adaptation to the microgravity environment; and 2) While wearing left-right reversing prism goggles during the CAPSULS mission. Both conditions significantly degraded motor performance but not cognitive performance. The data collected during both the MEMO experiment and the MWPE experiments enhance the knowledge base of human interface technology for human performance in extreme environments.

Adaptation, Psychological↗
PubMed1999

Effects of body orientation and rotation axis on pitch visual-vestibular interaction.

Spatial transformations of the vestibular-optokinetic system must account for changes in head position with respect to gravity in order to produce compensatory oculomotor responses. The purpose of this experiment was to study the influence of gravity on the vestibulo-ocular reflex (VOR) in darkness and on visual-vestibular interaction in the pitch plane in human subjects using two different comparisons: (1) Earth-horizontal axis (EHA) rotation about an upright versus a supine body orientation, and (2) Earth-horizontal versus Earth-vertical (EVA) rotation axes. Visual-vestibular responses (VVR) were evaluated by measuring the slow phase velocity of nystagmus induced during sinusoidal motion of the body in the pitch plane (at 0.2 Hz and 0.8 Hz) combined with a constant-velocity vertical optokinetic stimulation (at +/- 36 degrees/s). The results showed no significant effect on the gain or phase of the VOR in darkness or on the VVR responses at 0.8 Hz between EHA upright and EHA supine body orientations. However, there was a downward shift in the VOR bias in darkness in the supine orientation. There were systematic changes in VOR and VVR between EHA and EVA for 0.2 Hz, including a reduced modulation gain, increased phase lead, and decreased bias during EVA rotation. The same trend was also observed at 0.8 Hz, but at a lesser extent, presumably due to the effects of eccentric rotation in our EVA condition and/or to the different canal input across frequencies. The change in the bias at 0.2 Hz between rotation in darkness and rotation with an optokinetic stimulus was greater than the optokinetic responses without rotation. During EHA, changes in head position relative to gravity preserve graviceptor input to the VVR regardless of body orientation. However, the modifications in VVR gain and phase when the rotation axis is aligned with gravity indicate that this graviceptive information is important for providing compensatory eye movements during visual-vestibular interaction in the pitch plane.

Adult↗
PubMed1998

Effects of hypergravity on optokinetic after-nystagmus and perceived direction of optokinetic stimulation.

BACKGROUND: Previous observations made in parabolic flight and centrifuge studies have shown the presence of a vertical nystagmus (Lz-nystagmus) induced by changes in gravitoinertial forces, and its interaction with oculomotor reflexes. HYPOTHESIS: This Lz-nystagmus is also responsible for the changes in optokinetic after-nystagmus (OKAN) and the subjective perception of optokinetic stimulation direction during hypergravity. METHODS: OKAN was recorded during the 1.8-g phase of parabolic flight after exposure to horizontal or vertical optokinetic stimulation during the preceding 1.0-g or 0-g phases. Changes in the apparent direction of image motion in subjects presented with an optokinetic stimulus were investigated in another experiment where longer exposure to hypergravity was generated by flying an airplane along a spiral path. RESULTS: In upright subjects, the time constant of OKAN with slow phase up decreased during 1.8 g, whereas the horizontal OKAN showed no change in 1.8 g compared with OKAN recorded in 1.0 g. When the subjects were lying on their left side, the OKAN with slow phase right (slow phase up with respect to gravity) decreased in 1.8 g. The subjects tested showed larger error in setting the optokinetic stimulus in a pure horizontal plane in 1.8 g than in 1.0 g. The error was also larger for oblique stimulus in 1.8 g than in 1.0 g, but no differences were seen for the vertical stimulation. CONCLUSION: The changes in OKAN can be explained by an interaction between slow phase eye movements generated by OKAN and the Lz-nystagmus generated by change in the gravitational force level. The error of the perceived direction of the optokinetic stimulus measured during horizontal and oblique stimulation is also presumably due to the interaction between the visual system and the Lz-nystagmus generated by hypergravity.

Aerospace Medicine↗
PubMed1995

Human eye movement response to z-axis linear acceleration: the effect of varying the phase relationships between visual and vestibular inputs.

We investigated the effect of systematically varying the phase relationship between 0.5-Hz sinusoidal z-axis optokinetic (OKN) and linear acceleration stimuli upon the resulting vertical eye movement responses of five humans. Subjects lay supine on a linear sled which accelerated them sinusoidally along their z-axis at 0.4 g peak acceleration (peak velocity 1.25 m/s). A high-contrast, striped z-axis OKN stimulus moving sinusoidally at 0.5 Hz, 70 degrees/s peak velocity was presented either concurrently or with the acceleration stimulus or alone. Subjects' vertical eye movements were recorded using scleral search coils. When stimuli were paired in the naturally occurring relationship (e.g., visual stripes moving upward paired with downward physical acceleration), the response was enhanced over the response to the visual stimulus presented alone. When the stimuli were opposed (e.g., visual stripes moving upward during upward physical acceleration, a combination that does not occur naturally), the response was not significantly different from the response to the visual stimulus presented alone. Enhancement was maximized when the velocities of the visual and motion stimuli were in their normal phase relationship, while the response took intermediate values for other phase relationships. The phase of the response depended upon the phase difference between the two inputs. We suggest that linear self-motion processing looks at agreement between the two stimuli-a sensory conflict model.

Adult↗
PubMed1993

The role of brachial muscle spindle signals in assignment of visual direction.

1. In the oculobrachial illusion, a target light attached to the unseen stationary hand is perceived as moving and changing spatial position when illusory motion of the forearm is elicited by brachial muscle vibration. Our goal was to see whether we could induce apparent motion and displacement of two retinally fixed targets in opposite directions by the use of oculobrachial illusions. 2. We vibrated both biceps brachii, generating illusory movements of the two forearms in opposite directions, and measured any associated changes in perceived distance between target lights on the unseen stationary hands. The stability of visual fixation of one of the targets was also measured. 3. The seen distance between the stationary targets increased significantly when vibration induced an illusory increase in felt distance between the hands, both with binocular and monocular viewing. 4. Subjects maintained fixation accuracy equally well during vibration-induced illusory increases in visual target separation and in a no-vibration control condition. Fixation errors were not correlated with the extent or direction of illusory visual separation. 5. These findings indicate that brachial muscle spindle signals can contribute to an independent representation of felt target location in head-centric coordinates that can be interrelated with a visual representation of target location generated by retinal and oculomotor signals. 6. A model of how these representations are interrelated is proposed, and its relation to other intersensory interactions is discussed.

Arm↗
PubMed1991

Effects of static tilt about the roll axis on horizontal and vertical optokinetic nystagmus and optokinetic after-nystagmus in humans.

Horizontal and vertical OKN and OKAN were recorded in four conditions using the EOG technique. Instructions to subjects were aimed at obtaining a "look" type OKN. Two optokinetic stimulators, a stationary sphere and a binocular portable model, were compared with the subject in the upright condition. Three posture orientations, upright, 90 degree roll (horizontal), and upside-down, were then compared using the portable stimulator to determine the effect of roll-axis tilt on OKN at three velocities and on OKAN. Vertical OKN asymmetry was found to increase in the 90 degree roll position and to tend toward a reversal in the upside-down position. The time constant of vertical OKAN with slow phase up increased in both the 90 degree roll and upside-down positions. And finally, cross-coupled vertical eye movements during and after horizontal OKN were clearly observed. These results confirm the data obtained in monkeys, and are in accordance with the hypothesis of a three-dimensional organization of the velocity storage mechanism.

Electrooculography↗
PubMed1989

Effects of gravitoinertial force variations on vertical gaze direction during oculomotor reflexes and visual fixation.

Recordings of horizontal and vertical eye movement were obtained on eight subjects exposed to repeated patterns of vertical and horizontal optokinetic stimulation, visual fixation with a fixed or unseen target, and voluntary head oscillation in the high force and free-fall periods of parabolic flight. The downward shift of the beating field of vertical optokinetic nystagmus (OKN) observed in previous experiments was confirmed in the present study. The same directional shift was also noticed during optokinetic after-nystagmus (OKAN). Vertical direction of gaze clearly shifted downward during the decreased gravitoinertial force level when subjects were exposed to horizontal optokinetic stimulation, or when they attempted to track an unseen target in the dark with the head stationary or actively moved up and down. A vertical nystagmus with slow phases directed upward was observed during transition from high force level to free-fall when subjects were fixating their gaze on a stationary target. These findings are in agreement with those showing a general downward drive of the eyes on the first exposure to microgravity during orbital flight and an upward drive on the first day of return. Although this drive could be a consequence of a disorientation experienced by subjects undergoing parabolic flight or by astronauts, the phenomenon also supports the hypothesis of a tonic influence exerted by the otoliths on the postural and extra-ocular musculature in order to compensate for the downward pull by the gravitoinertial forces.

Adult↗