Functional organization of human supplementary motor cortex studied by electrical stimulation

• Published in: The Journal of neuroscience 1991-11, Vol.11 (11), p.3656-3666
• Main Authors: Fried, I, Katz, A, McCarthy, G, Sass, KJ, Williamson, P, Spencer, SS, Spencer, DD
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Biological and medical sciences; Brain Mapping; Electric Stimulation; Epilepsy - diagnosis; Epilepsy - physiopathology; Female; Functional Laterality; Fundamental and applied biological sciences. Psychology; Humans; Magnetic Resonance Imaging; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor Cortex - pathology; Motor Cortex - physiology; Sensation - physiology; Speech - physiology; Vertebrates: nervous system and sense organs
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.11-11-03656.1991

The presence of somatotopic organization in the human supplementary motor area (SMA) remains a controversial issue. In this study, subdural electrode grids were placed on the medial surface of the cerebral hemispheres in 13 patients with intractable epilepsy undergoing evaluation for surgical treatment. Electrical stimulation mapping with currents below the threshold of afterdischarges showed somatotopic organization of supplementary motor cortex with the lower extremities represented posteriorly, head and face most anteriorly, and the upper extremities between these two regions. Electrical stimulation often elicited synergistic and complex movements involving more than one joint. In transitional areas between neighboring somatotopic representations, stimulation evoked combined movements involving the body parts represented in these adjacent regions. Anterior to the supplementary motor representation of the face, vocalization and speech arrest or slowing of speech were evoked. Various sensations were elicited by electrical stimulation of SMA. In some cases a preliminary sensation of "urge" to perform a movement or anticipation that a movement was about to occur were evoked. Most responses were contralateral to the stimulated hemisphere. Ipsilateral and bilateral responses were elicited almost exclusively from the right (nondominant) hemisphere. These data suggest the presence of combined somatotopic organization and left-right specialization in human supplementary motor cortex.