Oculomotor control in children with cerebral palsy

Cerebral Palsy (CP) refers to non-progressive syndromes resulting from peri-/post-natal injury of the central nervous system. Children suffering from this neurological disorder show limitations in oculomotor control that are often thought to affect the executive functioning. In the present study, we assessed the attentional skills of CP children during the execution of lower-order cognitive tasks. To this end, we recorded ocular movements from 10 CP children (5 females, mean age: 11 years and 4 months ± 2 years and 10 months) during the execution of both a simple visually guided saccade task and a spatial cueing paradigm. In the cueing paradigm, 150 ms before the onset of an eye target, one of four placeholder around a central fixation cross briefly flashed (cue). The target randomly occurred at the same location of the cue (valid condition) or at a different one (invalid condition), and subjects had to direct the gaze towards it as fast as possible. Latency and accuracy of saccades recorded from CP subjects were compared with those of 13 children (6 males and 7 females, mean age: 13 years and 1 month ± 2 years and 6 months) with Typical Development (TD). Interestingly, the ocular performances during the simple visually guided saccade task did not differ between CP and TD subjects, being both groups quick to react to the onset of the ocular target. In the spatial cueing task, a coupling between cue location and gaze direction emerged, being saccadic latencies faster towards valid targets, both in TD and CP groups. However, CP children often executed gaze movements to the cue, suggesting a difficulty to inhibit an eye shift towards a task-irrelevant visual stimulus. Moreover, CP children frequently executed eye movements during the fixation of the central cross. Interestingly, these intrusive saccades were mostly aimed to one of the placeholder displayed in the visual scene. This behavior clearly suggests a difficulty of CP children to suppress eye movements towards locations exogenously and endogenously activated by visuo-spatial attention. By combining eyetracking techniques and cognitive protocols, the present study offers a new approach for studying executive function in patients suffering from limitations of voluntary motor control.