The role of the corpus callosum and bilaterally distributed motor pathways in the synchronization of bilateral upper-limb responses to lateralized light stimuli

(from the book) [the authors] review their work on reaction times for simple responses using axial, proximal, and distal muscles of the upper limbs in normal Ss and Ss with callosal deficit / demonstrate that the time needed for interhemispheric integration of crossed responses becomes much larger in patients with a callosal deficit and this is the case for unilateral and bilateral distal responses and unilateral proximal responses / it is inferred from these findings that the intact corpus callosum allows for efficient interhemispheric communication in order to secure integration of these responses / however, when proximal bilateral responses and unilateral and bilateral axial responses are made, other pathways are hypothesized to be responsible for integration / argue that a bilaterally distributed motor system secures the production of these symmetrical movements involving axial and proximal limb muscles, and this system can be called upon by each of both hemispheres