Visuomotor processing and hand force coordination in dyslexic children during a visually guided manipulation task.
Dyslexic children show loose visual tracking yet normal grip-force timing, so target the eyes before you blame the hand.
01Research in Context
What this study did
The team asked dyslexic and neurotypical children to pull a handle and match a moving line on a screen.
They measured how close the kids stayed to the target and how well they squeezed the handle.
The task was short and static—no reading involved, just eyes and hands.
What they found
Dyslexic kids drifted farther from the target line than peers.
Yet their grip force stayed in sync with load force, just like the controls.
Bottom line: the eye-hand link wobbled, but hand-hand timing held steady.
How this fits with other research
Hattier et al. (2011) saw the same pattern in standing still: dyslexic children swayed more when they had to use visual cues.
Cignetti et al. (2018) moved the question forward. They showed that only kids with both dyslexia and DCD had trouble planning the pull ahead of time.
The three papers line up: basic visuo-motor coupling is shaky in dyslexia, but grip timing stays intact unless another motor disorder is in the mix.
Why it matters
If a child with dyslexia knocks over a cup while reaching, the issue may be eye-hand tracking, not hand force.
You can keep strength-based handwriting drills, but add short visual tracking warm-ups—like tracing a slow-moving target on a tablet—to shore up the visual side.
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02At a glance
03Original abstract
Developmental Dyslexia negatively affects children's reading and writing ability and, in most cases, performance in sensorimotor tasks. These deficits have been associated with structural and functional alterations in the cerebellum and the posterior parietal cortex (PPC). Both neural structures are active during visually guided force control and in the coordination of load force (LF) and grip force (GF) during manipulation tasks. Surprisingly, both phenomena have not been investigated in dyslexic children. Therefore, the aim of this study was to compare dyslexic and non-dyslexic children regarding their visuomotor processing ability and GF-LF coordination during a static manipulation task. Thirteen dyslexic (8-14 YO) and 13 age- and sex-matched non-dyslexic (control) children participated in the study. They were asked to grasp a fixed instrumented handle using the tip of all digits and pull the handle upward exerting isometric force to match a ramp-and-hold force profile displayed in a computer monitor. Task performance (i.e., visuomotor coordination) was assessed by RMSE calculated in both ramp and hold phases. GF-LF coordination was assessed by the ratio between GF and LF (GF/LF) calculated at both phases and the maximum value of a cross-correlation function (rmax) and its respective time lag calculated at ramp phase. The results revealed that the RMSE at both phases was larger in dyslexic than in control children. However, we found that GF/LF, rmax, and time lags were similar between groups. Those findings indicate that dyslexic children have a mild deficit in visuomotor processing but preserved GF-LF coordination. Altogether, these findings suggested that dyslexic children could present mild structural and functional alterations in specific PPC or cerebellum areas that are directly related to visuomotor processing.
Research in developmental disabilities, 2014 · doi:10.1016/j.ridd.2014.06.002