Methods of functional brain imaging have been used to identify brain structures which are active during internal simulation of movements (ISM). Between 1977 and 1993 it was consistently reported that the primary motor cortex (MI) is not active during ISM whereas other cortical areas, in particular the supplementary motor area (SMA) are active. ISM was assumed to be a situation of "internal programming'. Brain systems involved in ISM or 'programming' were hypothesized to be superior to and separable from 'executive system' including MI. We have studied electric and magnetic fields of the brain when subjects internally simulated either a single movement or a sequence of movements. Results of the studies are consistent with the assumption that MI is active with ISM. Internally subjects experienced effort which was required to inhibit overt movements during ISM. A recent EEG study showed different patterns of cortical activity with ISM and with movement inhibition suggesting that different brain structures may be active during ISM and movement inhibition [23].