Abstract
We investigated coordinated movements between the eyes and head (“eye-head coordination”) in relation to vision for action. Several studies have measured eye and head movements during a single gaze shift, focusing on the mechanisms of motor control during eye-head coordination. However, in everyday life, gaze shifts occur sequentially and are accompanied by movements of the head and body. Under such conditions, visual cognitive processing influences eye movements and might also influence eye-head coordination because sequential gaze shifts include cycles of visual processing (fixation) and data acquisition (gaze shifts). In the present study, we examined how the eyes and head move in coordination during visual search in a large visual field. Subjects moved their eyes, head, and body without restriction inside a 360° visual display system. We found patterns of eye-head coordination that differed those observed in single gaze-shift studies. First, we frequently observed multiple saccades during one continuous head movement, and the contribution of head movement to gaze shifts increased as the number of saccades increased. This relationship between head movements and sequential gaze shifts suggests eye-head coordination over several saccade-fixation sequences; this could be related to cognitive processing because saccade-fixation cycles are the result of visual cognitive processing. Second, distribution bias of eye position during gaze fixation was highly correlated with head orientation. The distribution peak of eye position was biased in the same direction as head orientation. This influence of head orientation suggests that eye-head coordination is involved in gaze fixation, when the visual system processes retinal information. This further supports the role of eye-head coordination in visual cognitive processing.
Highlights
The relationship between action and visual cognition is a central issue in cognitive science and neuroscience [1, 2]
There was a single movement of the head and eyes, where the head and eyes moved in coordination as reported in previous studies of single gaze shifts
Using a visual search experiment in which the eyes, head, and body were allowed to move without restriction, the present study revealed three novel characteristics of eye-head coordination: 1) multiple saccades during a single head movement; 2) difference in eye-head coordination between the horizontal and vertical directions, which has been suggested, but not systematically analyzed [21, 28, 32,33,34,35]; and 3) an effect of head orientation on the distribution of eye positions when the visual system is processing retinal images
Summary
The relationship between action and visual cognition is a central issue in cognitive science and neuroscience [1, 2]. Interactions between body representation and movement and vision have been studied in a variety of experiments [3,4,5,6,7,8,9,10]. Demonstrated that tasks influence eye movements when subjects view a single picture [11]. The eyes and head move in coordination during gaze shifts, and a relationship between eye-head coordination and visual cognition is expected. Nakashima and Shioiri reported that performance was better when the visual stimulus was viewed straight ahead versus viewed laterally This illustrates the importance of eye-head coordination during visual cognition, suggesting that eye and head orientation is coordinated to shift gaze for high cognitive performance [15]
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