Horizontal saccadic eye movements enhance the retrieval of landmark shape and location information

Recent work has demonstrated that horizontal saccadic eye movements enhance verbal episodic memory retrieval, particularly in strongly right-handed individuals. The present experiments test three primary assumptions derived from this research. First, horizontal eye movements should facilitate episodic memory for both verbal and non-verbal information. Second, the benefits of horizontal eye movements should only be seen when they immediately precede tasks that demand right and left-hemisphere processing towards successful performance. Third, the benefits of horizontal eye movements should be most pronounced in the strongly right-handed. Two experiments confirmed these hypotheses: horizontal eye movements increased recognition sensitivity and decreased response times during a spatial memory test relative to both vertical eye movements and fixation. These effects were only seen when horizontal eye movements preceded episodic memory retrieval, and not when they preceded encoding (Experiment 1). Further, when eye movements preceded retrieval, they were only beneficial with recognition tests demanding a high degree of right and left-hemisphere activity (Experiment 2). In both experiments the beneficial effects of horizontal eye movements were greatest for strongly right-handed individuals. These results support recent work suggesting increased interhemispheric brain activity induced by bilateral horizontal eye movements, and extend this literature to the encoding and retrieval of landmark shape and location information.