Sustained effects for training of smooth pursuit plasticity

Maintaining orientation in space is a multisensory process, with the vestibular, visual, auditory and somatosensory systems as inputs. Since the input from each individual system changes, for example due to aging, the central nervous system must continuously adapt to these changes to maintain proper system performance. Changes can also be elicited by targeted modifications of the inputs, or by controlled training of sensory systems. While the effects of adaptation on eye movements elicited by the vestibulo-ocular reflex are well established, modifications of the efficacy of smooth pursuit eye movements are less well understood. We have investigated whether two 6-min training sessions on three subsequent days can induce lasting changes in the open- and closed-loop smooth pursuit performance of healthy, adult subjects. Ten subjects practiced making pursuit eye movements by tracking a target cross which moved quasi-randomly on a computer screen. Smooth pursuit performance was tested with a step-ramp paradigm immediately before and after the training, as well as 5 days after the last training session. Our results show that even such short training sessions can induce significant, lasting improvements in closed-loop smooth pursuit performance if the pursuit system of the subjects is challenged sufficiently during training. Control experiments on ten additional adult subjects who had their pursuit performance tested before and after a 20 min break without visual training confirmed that the pursuit enhancement is due to the visual training and not due to perceptual learning.