During interactions with our environment we must incorporate information about the mechanical properties of obstacles into our motor actions. Fundamental to these behaviors is the ability to simultaneously control movements of the hand while regulating the interaction forces that arise from contact with the environment. Although the neural control of movement has been studied extensively, there are few studies examining the ability to concurrently maintain contact forces with the environment.

This thesis addresses this limitation in knowledge by investigating how information about mechanical properties of the environment is incorporated into motor actions, and the neural control processes underlying these behaviors. Human psychophysics experiments are presented in which subjects interacted with robotic manipulanda rendering virtual environments. A model is also introduced to characterize subjects' interactions with the environment. Results show that the nervous system generates independent neural representations for the control of motions of the hand and forces at the hand/environment interface. A combination of these representations underlies interactions with the environment.