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Biomedical subjects

Fernanda Maciel

Publications and source records attributed to Fernanda Maciel.

3 recordsLinked to original sources
PubMed2004

Adjustment of the vestibulo-ocular reflex gain as a function of perceived target distance in humans.

The human vestibulo-ocular reflex (VOR) was investigated during active head movements in yaw while subjects were asked to view targets located at 20, 30, 40, 60, 90, and 120 cm distance aligned with eye level. Binocular video cameras were used to study conjugate eye movements and binocular convergence. Perceived target distance was determined during head oscillation by having the subjects move a cursor to the remembered position of the previously seen targets. The changes in VOR gain with viewing distance were found to be more closely related to perceived target distance than to actual target distance or fixation distance. This result suggests that the adjustment of VOR gain with viewing distance is under stronger cognitive control than would be expected of a simple motor reflex.

Adult↗
PubMed2002

Perception of tilt and ocular torsion of normal human subjects during eccentric rotation.

HYPOTHESIS: The authors hypothesized that a nonvisual measure of the subjective horizontal during eccentric rotation is a reliable method for evaluating the spatial orientation of normal subjects during such rotation. BACKGROUND: Eccentric rotation is a promising tool for the evaluation of otolithic function in healthy subjects and in patients. Although eye torsion is an objective measurement, it is also affected by angular acceleration/deceleration. Subjective horizontal is more accurately related to the changes in linear acceleration, but visual judgments of orientation are confounded by ocular torsion. METHODS: 20 subjects were tested during eccentric yaw rotation in both directions, generating centripetal acceleration directed along the interaural axis ranging from 0.38 g to 1 g. Perception of body tilt in roll and in pitch was recorded in darkness using verbal reports and a somatosensory plate that the subjects maintained parallel to the perceived horizon. Torsion of the eyes was recorded by a video camera. RESULTS: Perceived roll tilt was close to the tilt of the gravito-inertial acceleration vector. However, there were differences in perceived roll and pitch tilt between facing-motion and back-to-motion headings, presumably related to the direction of the tangential acceleration. Ocular torsion was dependent on both angular and centripetal accelerations. CONCLUSIONS: Measurement of perceived roll and pitch tilt using a somatosensory plate is a reproducible method for quantifying the effects of linear accelerations during eccentric rotation. This method may prove useful for the diagnosis of otolithic dysfunction in dizziness and in patients with vestibular disorders.

Acceleration↗