Cognitive control of saccadic eye movements in children with developmental coordination disorder

Fig 1. A) Cued and B) Non-Cued trials. Timings and target locations were predictable during the Cued condition, whilst target timings and locations were random in the Non-Cued condition. Targets (alien image) and cues (blast image) could appear at one of four locations from the centre fixation (earth image) point (90°, 180°, 270° and 360°). Central fixation was always present and the cue was always valid. Participants performed each condition with eyes only (EO), hand only (HO) and eyes and hand (EH). Fig 2. The reported data are for all saccades made within the trial that exceeded 2 ˚ in amplitude during the eye only (EO) task. Saccade duration and amplitude (main sequence) of TD children (A and C, left) and children with DCD (B and C, right) during Non-Cued (A and B, top graphs) and Cued (C and D, lower graphs) conditions. The graph shows the relationship between the saccade’s duration and corresponding amplitude. These included anticipatory saccades from the Cued conditions as these occurred in more than 50% of trials in the DCD group. All graphs show significant R2 values, which reveal a linear relationship between these saccade parameters in both groups and show the mean slopes obtained from each participant’s main sequence. Comparisons between group and condition did not reveal significant differences. Fig 3. Mean (and SEM) number of saccades per trial ratios for Non-Cued (A, left) and Cued (B, right) across EO, EH and HO blocks. The graph shows the ratio of larger saccades away from fixation, which was higher in the DCD compared to the TD group (DCD vs. TD, *). Lower panel. Mean number of saccades per trial (and SEM) during the presentation of the cue (250 ms) across Cued (EO, EH and HO) conditions (C). Overall, children with DCD exhibited greater number of saccades and thus, more inhibition errors compared to the TD group (DCD vs. TD, †). Fig 4. Mean (and SEM) Non-Cued (A) and Cued (B) saccade latencies across eye only (EO) and eye and hand (EH) tasks. Overall, the groups decreased saccade latencies in Cued conditions (Cued vs. Non-Cued, *). Lower panel. Mean Non-Cued (C) and Cued (D) saccade accuracy (and SEM) across eye only (EO) eye and hand (EH) tasks. Children with DCD (striped columns) exhibited increased absolute errors in the Cued conditions compared to the TD children (dark grey, D) and compared to the Non-Cued conditions (group by cue condition interaction, *†). However, there were no accuracy or latency differences between the groups in the Non-Cued conditions (C). Fig 5. Mean Non-Cued (A) and Cued (B) touch times (and SEM) from target onset across coordinated (EH) and hand only (HO) tasks. Both groups decreased HO touch times in the Cued compared to the Non-Cued conditions and compared to EH (Cued HO, *). Decreases in touch time seemed to be more evident in the DCD group (~ 343 ms difference) compared to the TD group (~ 100 ms difference), however, this result did not reach statistical significance. Lower panel. Mean Non-Cued (C) and Cued (D) touch accuracy (as mean absolute error and SEM) across EH and HO tasks. Children with DCD (striped columns) were less accurate compared to TD children (grey columns) in Cued (D) conditions (DCD vs. TD, †).