HOW PERCEIVED OBJECT DIMENSION INFLUENCES PREHENSION

A kinematic study assessed the effects of the perceived dimensions of an object upon the patterning of a prehension movement involving that object. If an apple was perceived as two-dimensional, subjects utilize d a large precision grip between the index finger and thumb. If the ap ple was perceived as three-dimensional, whole hand prehension involvin g all the digits was utilized. A visual perturbation from perceived tw o-dimensional to three-dimensional at movement onset resulted in a tra nsition from the 2D precision grip pattern to the 3D whole hand prehen sion. These results suggest that visual mechanisms for interpreting th e dimensions of an object directly influence motor selection pathways, and do not necessarily access a three-dimensional central nervous sys tem representation of the object.