Influence of cognitive functions and behavioral context on grasping kinematics.

We have documented before that human grasping movements executed in an everyday-like context differ from those in a typical laboratory context. The differences were reduced by factor analysis to five orthogonal factors; we took this as evidence that at least five distinct sensorimotor functions are context-dependent. To better understand how context exerts its influence on the sensorimotor system, we now evaluate the relationship between context-dependence and cognitive abilities. Forty subjects participated in a laboratory task (L) where grasping was explicitly instructed, externally triggered, repetitive, and served no higher ecologically valid purpose, or in an everyday-like task (E) where the movements were implicitly instructed, volitional, part of a behavioral sequence, and served a valid purpose. We registered a wide range of kinematic, force, and gaze parameters. Subjects also completed a battery of cognitive tests. We observed multiple task-related differences between grasping parameters, which could be reduced to five orthogonal factors by factor analysis with varimax rotation. Cognitive scores could also be reduced to five orthogonal factors. Five significant correlations between cognitive and grasping factors were observed and could be attributed to a linkage of cognitive abilities with E, with L, or with both tasks. Our data confirm that grasping movements are context-dependent and that this dependence can be traced back to five orthogonal factors. The observed correlations between cognitive and grasping factors are consistent with the view that behavioral context influences the distribution of processing between the ventral and the dorsal cortical stream.