O4‐03‐05: Eyetracking metrics of impaired spatial anticipation in behavioral variant frontotemporal dementia
Silvia Primativo, Camilla Neergaard Clark, Keir X. X. Yong, Jason D. Warren, Jonathan Daniel Rohrer, Sebastian James Crutch · Alzheimer s & Dementia · 2015
The dawn of pharmacological trials in FTD has further spurred the development of sensitive early markers of cognitive dysfunction. Eyetracking technology has had limited use in the dementia field to date, with most studies attempting to discriminate disease or syndrome subgroups on the basis of basic oculomotor functions. Here we exploit eye movement metrics to examine a specific component of executive function, namely spatial anticipation, in an adaptation of the paper and pencil Brixton spatial anticipation test. Thirteen behavioural variant FTD (bvFTD) patients, 7 semantic dementia (SD) patients and 38 age-matched healthy controls were presented with a 10x7 matrix of white circles. On each trial a black dot (filled in circle) moved across 7 positions on the screen. The passage of the target dot followed 12 different patterns balanced for pattern type (straight line, zig-zag, displaced zig-zag) and direction (up, down, left, right), with a variable inter-stimulus interval of 800-1200ms. Participants were asked to press a button as soon as they saw each target, whilst the time at which their eyes moved to the next (anticipated) target location was measured using a head-mounted infrared video-based eye tracker (Eyelink II; SR Research, Canada). The bvFTD, SD and control groups did not differ in terms of basic eye movement measures such as time to reaching the first target of the trial, suggesting that reflexive saccades were preserved. Both bvFTD and SD patients made fewer correct spatial anticipations to the location of forthcoming targets as compared with controls for all three pattern conditions. However, bvFTD patients made more erroneous anticipations compared to both SD patients and controls, suggesting a specific difficulty in anticipating subsequent events. Eye tracking measures provide insights into not only basic oculomotor function but also specific cognitive components of executive function in FTD. Difficulties in correctly programming and executing anticipatory eye movements during a spatial anticipation task may provide a specific marker of bvFTD. We are currently evaluating the sensitivity of this task relative to established cognitive and neuroimaging metrics to early cognitive change in individuals at genetic risk of developing FTD. Eyetracking adaptation of Burgess and Shallice's spatial anticipation test. Top Panel: Example zig zag pattern of target movement with a variable interval (800-1200ms) between stimulus onsets. Bottom Panel: Eyetracking data for one bvFTD patient (blue) and one control participant (red) relative to the position of the target (yellow). The bvFTD patient (blue) increasingly lags behind the control (red) in making the saccadic eye movement to the next target location. By the 6 target location, the control begins to move their eyes to the anticipated location of the next target prior to its actual appearance (example circled in red), whereas the bvFTD patient only ever shifts their gaze after the target has appeared (comparable saccadic shift circled in blue).