ELSEVIER Cognitive Brain Research 3 (1996) 125-129 COGNITIVE BRAIN RESEARCH Research report Electric and magnetic fields of the brain accompanying internal simulation of movement Wilfried Lang a,*7 Douglas Cheyne b Peter H611inger a, Willi Gerschlager Gerald Lindinger a a University Clinic of Neurology Vienna, Wiihringer Giirte118-20, A-1090 Vienna, Austria b Brain BehaviourLaboratory, School of Kinesiology, Simon Fraser University, Burnaby, B.C., Canada V5A 1S6 a Accepted 22 August 1995 Abstract 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]. Keywords: Motor imagery; Motor Cortex; Primary motor cortex; Magnetoencephalography 1. Introduction When we experience the ability to imagine or 'inter- nally simulate' a movement with its temporal and spatial sequencing we produce internal sensory images that resem- ble those which would arise when actually executing the movement. Furthermore, we experience effort to prevent overt movements during the performance of what we will refer to as the 'internal simulation of movement' (ISM). ISM was performed in the absence of overt movements. Subthreshold, task-specific muscular activity during ISM has been reported in some studies [17,34] but not in others (e.g. [27]). Several attempts have been made to identify brain structures which are activated during ISM: Ingvar and Philipson [16] measured changes of regional cerebral blood flow (rCBF) when subjects either executed rhythmic clenching movements of the right hand or imagined to do so. 'Motor ideation' as it was termed by these investiga- * Corresponding author. Fax: (43) (1) 40400/3141. 0926-6410/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0926-6410(95)00037-2 tors, caused increased rCBF in frontal and temporal areas but no changes in the rolandic area. The absence of MI-activity was taken as evidence that imagination of movements constitutes a state of 'pure mentation'. When subjects executed rhythmic movements blood flow in- creased mainly in the rolandic area. Roland et al. [27] studied changes of rCBF when subjects either executed or 'internally simulated' a sequence of self-paced thumb to digits oppositions, rCBF was found to increase exclusively in the SMA during 'internal simulation'. During execution of the same motor sequence rCBF increased in both SMAs and in the MI which was contralateral to the performing hand. The state of internal simulation of a movement was conceived to reflect the process of 'internal programming'. It was suggested that "the supplementary motor areas are programming areas for motor subroutines and that these areas form a queue of time-ordered motor commands before voluntary movements are executed by way of the primary motor area (p. 118)". Subsequent studies em- ployed different methods (SPECT, PET, functional MRI) and various tasks of ISM. It was consistently reported that SMA is active with internal simulation of movements but