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  • A Probabilistic Map of Functional Organization of the Human Ventral Sensorimotor Cortex (vSMC) by Cortical Electrical Stimulation

    Final Number:

    Jonathan D. Breshears MD; Edward F. Chang MD

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2013 Annual Meeting

    Introduction: In 1937, Penfield and Boldrey published their seminal work on the homuncular organization of human sensorimotor cortex. Despite playing an important role in speaking, eating, and oral gestures, the ventral half of the SMC (vSMC) remains understudied. In this study we qualitatively describe stimulation-evoked responses of the vSMC and determine the probability of observing a given response at any given cortical position when stimulated in an individual.

    Methods: Video, photographs, and MRI stereotactic co-registration images of intraoperative electrical stimulation of the vSMC were collected for patients undergoing awake craniotomy. Stimulation sites were converted to a 2D coordinate system based on anatomic landmarks. Patient responses to stimulation were iteratively reviewed & classified. Probabilistic maps of stimulation responses were generated.

    Results: In 33 patients, we identified 194 motor, 212 sensory, 61 speech arrest, and 27 mixed responses. Responses were complex, stereotyped, and mostly non-physiologic movements, involving hand, orofacial, and laryngeal musculature. Within individuals, the presence of complete representation of the oral movements varied, however the dorsal-ventral order was maintained. The most robust motor responses were: jaw (probability = 0.85), tongue (0.64), lips (0.58), and throat (0.52). Vocalizations were seen in 6 patients (0.18) near lip and dorsal throat areas. Sensory responses were spatially dispersed however patients’ subjective reports were highly precise in localization to parts of the mouth. The most robust included: tongue (0.82), and lip (0.42). The probability of speech arrest was 0.82, highest 15 - 20 mm anterior to the central sulcus and just dorsal to the Sylvian fissure.

    Conclusions: We report probabilistic maps of function in the human vSMC based on intraoperative cortical electrical stimulation. These results define the expected range of mapping outcomes in the vSMC of a single individual, and shed light about the functional organization of the vSMC supporting speech motor control and non-speech functions.

    Patient Care: Improved understanding of the functional organization of the vSMC will lead to improved mapping, safer resections, and a better understanding of speech motor control.

    Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the expected responses to cortical electrical stimulation of the vSMC 2) Discuss the range of individual variability in responses to stimulation 3) Describe the spatial probability distribution of a given stimulation response in the vSMC

    References: 1. Penfield, W. and E. Boldrey, Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation. Brain, 1937. 60(4): p. 389-443. 2. Nii, Y., et al., Does the central sulcus divide motor and sensory functions? Cortical mapping of human hand areas as revealed by electrical stimulation through subdural grid electrodes. Neurology, 1996. 46(2): p. 360-7. 3. Graziano, M.S., C.S. Taylor, and T. Moore, Complex movements evoked by microstimulation of precentral cortex. Neuron, 2002. 34(5): p. 841-51. 4. Woolsey, C.N., T.C. Erickson, and W.E. Gilson, Localization in somatic sensory and motor areas of human cerebral cortex as determined by direct recording of evoked potentials and electrical stimulation. J Neurosurg, 1979. 51(4): p. 476-506. 5. Meier, J.D., et al., Complex organization of human primary motor cortex: a high-resolution fMRI study. J Neurophysiol, 2008. 100(4): p. 1800-12. 6. Takai, O., S. Brown, and M. Liotti, Representation of the speech effectors in the human motor cortex: somatotopy or overlap? Brain Lang, 2010. 113(1): p. 39-44. 7. Ojemann, G., et al., Cortical language localization in left, dominant hemisphere. An electrical stimulation mapping investigation in 117 patients. J Neurosurg, 1989. 71(3): p. 316-26. 8. Haglund, M.M., et al., Cortical localization of temporal lobe language sites in patients with gliomas. Neurosurgery, 1994. 34(4): p. 567-76; discussion 576. 9. Penfield, W. and K. Welch, Instability of response to stimulation of the sensorimotor cortex of man. J Physiol, 1949. 109(3-4): p. 358-65, illust. 10. Brown, S., E. Ngan, and M. Liotti, A larynx area in the human motor cortex. Cereb Cortex, 2008. 18(4): p. 837-45. 11. Brown, S., et al., The somatotopy of speech: phonation and articulation in the human motor cortex. Brain Cogn, 2009. 70(1): p. 31-41. 12. Bouchard, K.E., et al., Functional organization of human sensorimotor cortex for speech articulation. Nature, 2013. 495(7441): p. 327-32. 13. Penfield, W. and T. Rasmussen, Vocalization and arrest of speech. Arch Neurol Psychiatry, 1949. 61(1): p. 21-7. 14. Loucks, T.M., et al., Human brain activation during phonation and exhalation: common volitional control for two upper airway functions. Neuroimage, 2007. 36(1): p. 131-43.

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