Eye–Head Coordination during Free Exploration in Human and Cat

Abstract

Eye, head, and body movements jointly control the direction of gaze and the stability of retinal images in most mammalian species. The contribution of the individual movement components, however, will largely depend on the ecological niche the animal occupies and the layout of the animal's retina, in particular its photoreceptor density distribution. Here the relative contribution of eye-in-head and head-in-world movements in cats is measured, and the results are compared to recent human data. For the cat, a lightweight custom-made head-mounted video setup was used (CatCam). Human data were acquired with the novel EyeSeeCam device, which measures eye position to control a gaze-contingent camera in real time. For both species, analysis was based on simultaneous recordings of eye and head movements during free exploration of a natural environment. Despite the substantial differences in ecological niche, photoreceptor density, and saccade frequency, eye-movement characteristics in both species are remarkably similar. Coordinated eye and head movements dominate the dynamics of the retinal input. Interestingly, compensatory (gaze-stabilizing) movements play a more dominant role in humans than they do in cats. This finding was interpreted to be a consequence of substantially different timescales for head movements, with cats' head movements showing about a 5-fold faster dynamics than humans. For both species, models and laboratory experiments therefore need to account for this rich input dynamic to obtain validity for ecologically realistic settings.

Two distinct types of eye-head coupling in freely moving mice

“…Indeed, we show that a major aspect of mouse eye movements is the stabilization of retinal stimulation during head rotation. Gaze shifting saccades were typically coupled to head rotations and mice made about 12 gaze shifts per second, similar to humans (Einhäuser et al, 2009). We considered the possibility that these horizontal gaze movements reected overt visual attention.…”

“…5%) by eye movements alone. Moreover, similar to other animals like cats (Guitton et al, 1984, Guitton, 1992, Einhäuser et al, 2009) and marmosets (Mitchell et al, 2014), mice may be able to rely more heavily on head movement to shift gaze, since they can move the head much faster than monkeys and humans with bigger heads that need to overcome much larger inertial forces. Finally, relying as much as possible on head movements as opposed to eye-in-head movements at the behavioral level reduces the computational burden on the brain to compute this early stage egocentric transformation as it seeks to integrate information from the dierent sensory modalities in the construction of an allocentric representation of the world.…”

Driving Simulation in the Clinic: Testing Visual Exploratory Behavior in Daily Life Activities in Patients with Visual Field Defects

“…Define sections between saccades as fixations. Define head-movements as movements exceeding 6° /sec 11 and an amplitude of more than 3°. Exclude simultaneous headand eye-movements with directory in the opposite direction as they represent no gain in gaze amplitude.…”

Gaze allocation in natural stimuli: Comparing free exploration to head-fixed viewing conditions

“…EyeÁhead-coordination analysis suggested a profound influence of nonsaccadic eye movements to gaze-centred stimulus statistics (Einhäuser et al, 2007;Einhäuser, Moeller, et al, 2009), and the spatial statistics of features at the centre of gaze transferred the concept of feature saliency from the laboratory to the real world Schumann et al, 2008). A direct comparison between free exploration and laboratory data with the same visual input has, however, yet to be performed.…”