Tactile afferent input influencing motor coordination during precision grip

The remarkable capacity and versatility of the human hand in precise manipula-tory tasks is undoubtedly dependent upon a number of neural factors. One such factor is the tactile sensory innervation of the glabrous skin area, i.e. the hairless skin of the volar aspect of the hand. Indeed, Mott and Sherrington [22], dealing with the motor effects of various patterns of dorsal root sections in Macacus rhesus, found that "afferent impulses, both from the skin and from muscles, espe-cially the former, as related to the palm and sole, are necessary for the carrying out of 'highest level ' movements. " Likewise, Denny-Brown [5] wrote extensively on the capacity of tactile stimuli in eliciting prepatterned integrated hand move-ments in clinical and experimental material. In patients with frontal lobe lesions, automatic prehensile movements of at least two types could be distinguished: the "grasp reflex " and the more complex "instinctive grasp reaction". In contrast, during parietal lobe lesions, "tactile avoiding reactions " of different complexities were described. The pathological feature of these reactions was considered to be an inability to adequately suppress the first phase, i.e. the reactions appeared t