Abstract
Despite numerous reports of abnormalities in limb motor controls in spatial orientation in individuals with autism spectrum disorder (ASD), the underlying mechanisms have not been elucidated. We studied the influence of allocentric coordinates on ongoing reaching movements, which has been reported to strongly affect the reaching movements of typically developing (TD) individuals. ASD and TD participants observed a target presented randomly on one of the four corners of a frame on a screen. After it disappeared, another frame was presented slightly shifted leftward/rightward. The participants touched the memorized position of the target relatively congruent with a reference frame (allocentric condition) or ignoring it (egocentric condition). Results suggested that TD individuals were apt to touch the positions in allocentric manner rather than egocentric manner, while ASDs did not show this prioritization. Our findings demonstrate that decreased utilization of visual landmarks in ongoing movement may underlie motor disabilities in autism.
Highlights
Individuals with autism spectrum disorders (ASD) often show poorer fine motor skills such as handwriting, drawing and ball handling [1]
We examined to what extent individuals with ASD depend on visual information of surrounded environment in feedback-absent reaching behaviour
Our present findings suggest that preferential utilization of allocentric coordination over egocentric coordination in immediate ongoing movements before acquiring an internal model [4,5,6] evident in typically developing (TD) individuals but not in individuals with ASD
Summary
Individuals with autism spectrum disorders (ASD) often show poorer fine motor skills such as handwriting, drawing and ball handling [1]. While visual information of target object is useful in acquiring internal model for adaptive motor controls in typically developing (TD) children [3], children with ASD tended to put greater reliance on proprioceptive feedbacks in motor learning [4, 5] This character was found to relate to reduced synaptic volume especially in the cerebellum which is a representative neural basis of internal models of motor control [6]. From these findings, different optimizing strategies of motor control in internal model would be responsible for difficulty to learn adaptive movements. Recognition of the object itself and recognition of it in relation to surrounding environment of the object, that is, allocentric coordinates, is useful for efficient goal-directed
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