Eye-head coupling in humans

Abstract

A tonic coupling between the horizontal component of eye position and dorsal neck muscle activity has been demonstrated in the cat and monkey. In order to demonstrate this synergy in humans and study its characteristics, we have measured the relation between the firing rate of individual motor unit of the splenius muscle and voluntary horizontal shifts of gaze using 5 degrees steps, in head-fixed subjects. Eye movement recording was achieved by conventional binocular electro-oculography and the activity of the right splenius muscle was recorded with Bronks coaxial bipolar electrodes inserted manually at the C4-C5 intervertebral level. The activity of 51 motor units in 10 subjects has been recorded. For all subjects, motor units firing rate increased when the gaze shifted to the ipsilateral side, and both increase in firing rate and recruitment were observed. These results demonstrate that the tonic eye head synergy is also present in man.

Interaction between the oculomotor and postural systems during a dual-task: Compensatory reductions in head sway following visually-induced postural perturbations promote the production of accurate double-step saccades in standing human adults

“…Moreover, it was reported using a variety of techniques that neck muscle modulations (head-turning synergies) are observed in many species, including humans, during small amplitude (and medium) gaze shifts (≈5–20°) and eye-in-head deviations smaller than 15 degrees [40–50]; for a discussion see Corneil and Munoz [51]. Before calculating eye displacements, we therefore made sure that subjects did not concomitantly rotate their head as they gazed at the different visual targets and therefore kept the head pointing forward at all time.…”

Role of ocular convergence in the Romberg quotient

“…Recall that proprioception of extra-ocular muscles is rich and there is a synergy between extra-ocular muscles proprioception and neck muscles proprioception [33]. In man head fixed, tonic and dynamic coupling of the extra-ocular muscles discharge with neck muscles discharge had been shown earlier [34,35]. Finally, EEG study showed that convergence of eyes activated highly several posterior and central cortical areas [36].…”

Adaptive Gaze Strategies for Locomotion with Constricted Visual Field

“…In our RP subjects, changes in head direction were associated with larger REMs. Indeed, following the well-established principle of eye-head synergy (André-Deshays et al, 1988), a relevant contribution of head movements is more likely to occur with larger gaze shift (>20°; Freedman, 2008). …”