Tug-of-Peace: Visual Rivalry and Atypical Visual Motion Processing in MECP2 Duplication Syndrome of Autism

Bistable OKN responses under visual rivalry. A, Bistable moving plaid stimulus. Type I symmetric plaid is composed by summing two 50% contrast component gratings. The gratings move at an angle of 120° relative to each other. This plaid can be seen either as two individual gratings moving at an angle or as a sum of gratings integrated percept of pattern motion. The direction of pattern motion lies in between the directions of motion of each grating. Thus, the observer can follow three directions of motion (lower panel): pattern motion (direction set at 0°) and either of the component grating’s drift, offset at +60° and –60° from the vector of the plaid’s motion (insets). B, Experimental setup. We presented the stimuli on two screens positioned at equal distances from the mouse head to cover 180° of the mouse ipsilateral visual field. We head-posted the mouse to prevent head movements and monitored eye movements with an infrared camera. The mouse could walk freely on the free-moving wheel. Green arrows indicate the direction of the global drift of the stimulus. The stimulus was moving toward the mouse’s nose to induce robust optokinetic movements. C, D, E, Data preprocessing pipeline. C, OKN images were collected at 300 Hz and 20 randomly selected mouse pupil movies were used to train Deep Lab Cut ResNET-150 model to extract the position and size of the animal’s pupil during the OKN (colored dots DeepLabCut feature detection). D, The vertical and horizontal components of the OKN were sorted into saccade-pursuit eye movement pairs, and eye-blink and grooming-related artifacts were located using custom-written Python toolbox “Dolia” and excluded from analysis. E, The pursuit phases of the OKN eye movements were fitted with a linear polynomial fit. The ratio between fitted vertical and horizontal component of each eye movement was then used to determine its direction (angle). Pink and blue histograms show the example distributions of eye movement directions from two different 15-min OKN movies. Using the ratio of the vertical and horizontal components’ amplitudes, the directions of the eye movements were determined (for details, see Materials and Methods). Right, Distributions of the directions of pursuit phases of OKN for two different OKN movies. F, G, Grating-induced OKN. To determine the location of zero direction (pattern motion direction) and classify eye movements as aligned with pattern motion or alternatively the motion of the components, we used OKN data obtained by presenting the zero-direction grating moving in temporonasal direction, similarly to the plaid setup. Since such a grating has only one unambiguous direction of drift, it is possible to use the mean of the eye movement direction distribution as a zero direction. Additionally, [–SD, +SD] can be set as a bracket in which most eye movements aligned with zero direction fall (E). The grating-induced OKN is shown in F: as expected, OKN eye movements contain a sole horizontal component (black trace), with no consistent vertical deflections (red trace), and this stimulus does not result in visual rivalry as only one interpretation of the stimulus is possible. In G, the distribution of grating-induced OKN is shown (yellow histogram, 13 zero-direction grating movies from 13 animals were used to determine zero position, and the SD bracket for eye movement classification). [–SD, +SD] interval around the zero direction is then applied to plaid OKN data: the eye movements with directions inside this interval are classified as pattern-motion aligned, while eye movements with directions outside of this interval are classified as component-motion aligned (G, blue histogram). H, I, Plaid-induced OKN shows bistable reversals of the eye movement directions. In H, the mouse can follow either the plaid or the grating direction while observing the unchanging plaid stimulus. Green dotted line indicates location of the perceptual switch, defined as the start of the saccade where the animal starts following a different stimulus interpretation. Initially, the animal follows a pattern motion direction; after the reversal, a solid vertical component appears (red trace) as the animal stops following the pattern motion and starts following the +60° component. I, Blue histogram, The EM directions distribution of OKN induced by a plaid stimulus. Gray dotted lines correspond to the pattern-component OKN bracket derived from grating OKN data (see the yellow histogram in G). Plaid OKN: central peak corresponding to pattern-motion aligned eye movements as well as two additional peaks located at approximately +60° and –60° off the central peak and corresponding to component motion-aligned OKN.