Abstracts

Rationale: The cingulate gyrus is a major part of the limbic system, classically attributed the function of mediating emotional responses. Its complex connectivity pattern and the information provided by stimulation studies suggest that it is a functionally heterogeneous structure.The rich connectivity of the anterior and mid cingulum (A-MC) to the motor cortex and spinal cord, the dense reciprocal cortico–cortical connections with the lateral prefrontal cortex and the extensive afferents from the midline thalamus and the brainstem nuclei support its role in motor control, cognition and autonomic functions. We aim to characterize the responses of the A-MC to direct electrical cortical stimulation (DCS) to further understand the function of the different subregions of the cingulate, and to generate a functional map of the cingulate. Methods: Forty-eight patients with intracranial depth electrodes placed in the mid and anterior cingulate for presurgical diagnostics underwent DCS for mapping purposes (bipolar, biphasic intensities of 1-7mA, 50 Hz).The responses were recorded and classified as motor, sensory, autonomic and emotional responses, change in the perception of body position, unspecific experiences and no responses.The spatially discrete cortical stimulation-derived data points based on electrode location on MRI were then transformed into continuous probabilistic maps, enabling voxel-wise spatial inference for each response type on the cingulum. Results: A total of sixty pairs of electrodes in 48 patients were stimulated and its responses recorded and classified. In two patients a seizure was triggered by DCS and these sites were excluded.In 15 patients (33%) motor responses were triggered. In 8 of those the motor response consisted of stereotypical complex movement involving trunk and all four limbs (contralateral>ipsilateral). The complex action was adapted to the environment integrating the surrounding objects present (i.e bedsides, linen).Sensory responses were obtained in 9 patients, autonomic responses in 6, change in the perception of body position in 5, emotional responses in 4 and unspecific experiences in another 4. In 6 patients the response had more than one component (i.e. motor and emotional). A functional map of stimulation findings of the cingulum emerged. Conclusions: This case series study reveals that the cingulate gyrus has a heterogeneous functional organization comprising motor, autonomic, emotional, sensory and body position responses. Stereotyped complex movements suggest that highly automatic adaptive motor responses can be activated using DCS of the A-MC, often integrating other components such as emotional, change in body position perception, autonomic or sensory responses. This suggest the cingulate may play a key hub role integrating these responses. Funding: National Institute for Health Research, National Institute of Neurological Disorders and Stroke, Capability Funding and Guarantors of Brain; The Wellcome Trust, the Department of Health. University College London Hospitals Biomedical Research Centre and the Wolfson Foundation