Abstracts

Rationale: Although volition and complexity of an action often go hand-in-hand, rapid, automatic movements must sometimes be remarkably complex. Complex motor responses may be pre-encoded and ready to be executed in response to certain situations. These may represent an efficient way of the motor system to confront situations in which reaction time is of relevance. Falling, for example, requires an instant response to the potential consequences that necessarily integrates a multiplicity of facts about the state of the body and its environment. The anterior/mid cingulum (A-MC) is a potential node where motor control, emotional, and vegetative responses may integrate. It has been involved in the production of stereotypical complex motor responses limited to small body areas (Talairach et al., 1973). The A-MC has also been called part of “the human vestibular cortex” as it is involved in the sensation of body movement (Kahane et al., 2003). Here we report a case series of complex, rapid, stereotyped motor actions associated with sensations of body position change triggered by direct electrical cortical stimulation of the ventral aspect A-MC. Methods: Twenty patients had intracranial depth electrodes placed in the mid and anterior cingulate for epilepsy presurgical investigations. Direct electrical cortical stimulation (DCS) was performed in a bipolar manner, using intensities of 1-7mA at 50 Hz. Once a response was elicited, it was reproduced several times. Motor, sensory, emotional, and vegetative responses were recorded.The responses were classified as complex motor responses, change in position perception and emotional responses. Results: Stereotypical complex motor responses were observed in 10 out of 20 patients. Motor responses involved trunk and all four limbs (contralateral>ipsilateral). The complex action was adapted to the environment; patients would stereotypically grasp the cot sides for example, and were unable to suppress such movements. The motor response was associated with a sensation of change in body position in 50% of the subjects. Twenty % of the patients reported an associated emotion.In 2 patients, there was a sensation of change of body position or an emotion without motor response. Conclusions: This case series study reveals that complex, yet highly automatic, motor patterns can be activated using DCS of the A-MC, often in association with sensations of change in body position. This suggests that A-MC is key in integrating body position information and retrieving rapid, adaptive motor patterns in response. Funding: This work was undertaken at UCLH/UCL who receives a proportion of funding from the Department of Health’s NIHR Biomedical Research Centres funding scheme.  We are grateful to the Wolfson Foundation and the Epilepsy Society for supporting the Epilepsy Society MRI scanner. BD received support by the NIH – National Institute of Neurological Disorders and Stroke U01-NS090407 (The Center for SUDEP Research). AJ is funded by Guarantors of Brain and NIHR ULCH Biomedical Research Centre.PN is funded by the Wellcome Trust and the Department of Health