The interfering influences by which the different components of the early somatosensory evoked potentials are modified are reviewed from both neurophysiologic and clinical perspectives. Special consideration is given to the specific differences between sensory and motor interferences. In this context, the specific effect of the mental movement simulation task on the frontal N30 component is discussed in relation to the involvement of this evoked wave as a physiologic index of the dopaminergic motor pathways. Relevant interfering approaches, including concurrent events ranging from tactile stimulation to locomotion, are reviewed and discussed insofar as these data provide insights into the neurophysiologic processes of interaction between competing internal models controlling motor acts and sensory information.