Human eye-head coordination in two dimensions under different sensorimotor conditions

• Published in: Experimental brain research Vol. 114; no. 3; pp. 542 - 560
• Main Authors: Goossens, H. H. L. M., Opstal, A. J. Van
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.05.1997
• Subjects: Acoustic Stimulation; Adult; Biological and medical sciences; Female; Fixation, Ocular - physiology; Fundamental and applied biological sciences. Psychology; Head Movements - physiology; Humans; Kinesthesis; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Photic Stimulation; Psychomotor Performance - physiology; Saccades - physiology; Vertebrates: nervous system and sense organs; Human; Sensorimotor coordination; Visual stimulus; Acoustic stimulus; Motor pathway; Visual pathway; Gaze; Eye head coordination; Auditory pathway; Motor control; Saccadic eye movement
• ISSN: 0014-4819
• DOI: 10.1007/PL00005663

The coordination between eye and head movements during a rapid orienting gaze shift has been investigated mainly when subjects made horizontal movements towards visual targets with the eyes starting at the centre of the orbit. Under these conditions, it is difficult to identify the signals driving the two motor systems, because their initial motor errors are identical and equal to the coordinates of the sensory stimulus (i.e. retinal error). In this paper, we investigate head-free gaze saccades of human subjects towards visual as well as auditory stimuli presented in the two-dimensional frontal plane, under both aligned and unaligned initial fixation conditions. Although the basic patterns for eye and head movements were qualitatively comparable for both stimulus modalities, systematic differences were also obtained under aligned conditions, suggesting a task-dependent movement strategy. Auditory-evoked gaze shifts were endowed with smaller eye-head latency differences, consistently larger head movements and smaller concomitant ocular saccades than visually triggered movements. By testing gaze control for eccentric initial eye positions, we found that the head displacement vector was best related to the initial head motor-error (target-re-head), rather than to the initial gaze error (target-re-eye), regardless of target modality. These findings suggest an independent control of the eye and head motor systems by commands in different frames of reference. However, we also observed a systematic influence of the oculomotor response on the properties of the evoked head movements, indicating a subtle coupling between the two systems. The results are discussed in view of current eye-head coordination models.