| Popis: |
A basic issue is to determine whether the probability of obtaining eye–head coupling depends upon the stimulus location in the visual field. The experiment in this chapter investigated the effect of target direction on both oculomotor activity and head coupling in a pursuit task. Two age groups were compared: neonates (three days old) and young infants (forty-five days old). Horizontal eye movements were measured from EOG recordings and were also recorded by a video camera. A second camera filmed head movements. The data show that pursuit is more extended when the target moves from the periphery to the centre (P→C) at both ages. In most cases, smooth pursuit is performed in the central region of the visual field (0−24°), regardless of whether the starting point of the target is central or peripheral. To analyse eye–head coupling, the portion of smooth pursuit performed with ipsilateral head movements was examined. There was more smooth pursuit in the forty-five-day-old infants than in the neonates, and more in the centre-to-periphery (C→P) condition than in the periphery-to-centre condition. The findings of this study shows that the extent of visual pursuit is greater when the target moves from the periphery to the central visual field but, in this direction of motion, more saccades are observed than in the opposite direction. |
