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Electrical stimulation of the superior colliculus (SC) in alert cats free to move their head, evoked coordinate eye and head movements. The characteristics of these movements as well as their mode of coordination differed according to the collicular region being explored. Three zones were distinguished. In the anterior zone, evoked eye saccades were(More)
Using 15O-water 3D positron emission tomography, regional cerebral blood flow was measured twice in six human subjects: before and after extensive training in orientation discrimination. In each session subjects performed two orientation discrimination tasks, during which they discriminated the orientation of a grating at either the trained or untrained(More)
Electrical stimulation of the cat superior colliculus (SC), in conjunction with the accurate measurement of elicited eye movements and histologically verified electrode positions, has revealed a striking antero-posterior variation in collicular organization. Three zones could be defined in the SC on the basis of eye movement patterns and associated neck(More)
Visual fixation and pursuit abilities of human infants were tested during their first year of life. Eye as well as head position was measured. Results show that the fixation of visual targets is accomplished by a head rotation accompanied by a series of small eye saccades. The number of these saccades increases with target eccentricity but progressively(More)
Positron emission tomography (PET) was used to investigate the functional anatomy of the foveal fixation system in 10 subjects scanned under three different conditions: at rest (REST), during the fixation of a central point (FIX), and while fixating the same foveal target during the presentation of peripheral visual distractors (DIS). Compared with the REST(More)
Head-fixed gaze shifts were evoked by electrical stimulation of the deeper layers of the cat superior colliculus (SC). After a short latency, saccades were triggered with kinematics similar to those of visually guided saccades. When electrical stimulation was maintained for more than 150-200 ms, postsaccadic smooth eye movements (SEMs) were observed. These(More)
The electromyographic (EMG) activity of different neck muscles in relation to gaze orientation has been studied in alert trained cats. When the head is kept fixed, the activity of these muscles is proportional to eye eccentricity in the horizontal as well as in the vertical planes. On basis of this tonic activity, a preferential orientation can be(More)
(1) The electrical stimulation of the superior colliculus (SC) in the cat evokes exclusively conjugate and contraversive eye saccades. (2) Their maximum velocity is markedly higher than that of spontaneous saccades. (3) The stimulus parameters (intensity, frequency, pulse width) have but little effect on the characteristics of the saccades. (4) In the(More)
The present report studied the contingent negative variation during Gap and Non-Gap conditions using visual stimulation and manual responses. The reaction times during the Gap condition were facilitated compared with those of the Non-Gap condition. The contingent negative variation component was obtained during the preparatory period from electrodes placed(More)