Search PubMed⌕ Search

Biomedical subjects

C Ghez

Publications and source records attributed to C Ghez.

64 records · Page 4Linked to original sources
PubMed1972

Physiological correlates of adaptation to a rotated visual field.

1. Perceptual adaptation to a 30 or 45 degrees visual tilt was induced in human subjects by means of prismatic spectacles worn for 5-7 days. Relative contrast thresholds and the amplitudes of the occipital potentials to vertical and oblique gratings were studied.2. During continuous exposure to the tilted visual environment the normal differences between contrast thresholds for vertical and oblique targets decreased or were no longer significant. In all subjects the change from control threshold differences was significant at the 0.005 level.3. During the course of adaptation the difference in amplitude of the potentials evoked by vertical and oblique oscillating gratings also decreased. The changes with respect to control differences were significant at the 0.005 level in each subject.4. Intermittent exposure to tilt in one subject resulted only in minor adaptation of the apparent vertical, and the evoked potential differences did not change from control levels.5. The changes are interpreted as suggesting that plastic changes in the extraretinal mechanism responsive to target orientation occur during adaptation to prismatic tilt.

Adaptation, Ocular↗
PubMedDate not supplied

Red nucleus and motor cortex: parallel motor systems for the initiation and control of skilled movement.

This study examines the differential contributions of motor cortex (MCx) and red nucleus (RN) neurons to the initiation of a targeted limb response and to the control of trajectory. These questions were assessed in two ways. First, by comparing the characteristics of task-related neuronal activity in MCx and RN. Second, by determining the changes in reaction time and trajectories produced by the reversible inactivation of corticospinal fibers in the crus cerebri (CSTc), the rubrospinal tract (RST) and the RN, using microinjections of lidocaine, gamma-aminobutyric acid, or muscimol. Neurons in forelimb areas of both MCx and RN were modulated in advance of forelimb force production. RN neurons more frequently had a phasic discharge pattern, while neurons in MCx more frequently had a tonic pattern. Whereas the modulation of most forelimb area neurons in MCx correlated with responses in a specific direction, the majority of RN neurons were non-directional. Reversible inactivation of CSTc, RN and RST prolonged reaction time. The normal stereotyped form of isometric force trajectories was unaffected by injections at any site. While CSTc inactivation resulted in hypometric responses, response amplitude was unchanged during RN and RST inactivation. We conclude that both MCx and RN contribute to response initiation, but that only MCx is involved in the proper scaling of targeted responses.

Animals↗