Editing Motor cortex (section)

===The supplementary motor cortex===
Penfield<ref name=Penfield&Welch>{{cite journal |author1=Penfield, W.  |author2=Welch, K  | year=1951 | title=The supplementary motor area of the cerebral cortex: A clinical and experimental study | journal=A.M.A. Arch. Neurol. Psychiatry | volume=66 | pages=289–317 | pmid = 14867993 | doi=10.1001/archneurpsyc.1951.02320090038004 | issue=3}}</ref> described a cortical motor area, the supplementary motor area (SMA), on the top or dorsal part of the cortex. Each neuron in the SMA may influence many muscles, many body parts, and both sides of the body.<ref name=Gould&etal>{{cite journal | author=Gould, H.J. III, Cusick, C.G., Pons, T.P. and Kaas, J.H | year=1996 | title=The relationship of corpus callosum connections to electrical stimulation maps of motor, supplementary motor, and the frontal eye fields in owl monkeys | journal=J. Comp. Neurol. | volume=247 | pages=297–325 | pmid=3722441 | issue=3 | doi=10.1002/cne.902470303| s2cid=21185898 }}</ref><ref name=Luppino&etal>{{cite journal | author=Luppino, G., Matelli, M., Camarda, R.M., Gallese, V. and Rizzolatti, G | year=1991 | title=Multiple representations of body movements in mesial area 6 and the adjacent cingulate cortex: an intracortical microstimulation study in the macaque monkey | journal=J. Comp. Neurol. | volume=311 | pages=463–482 | doi=10.1002/cne.903110403 | pmid=1757598 | issue=4| s2cid=25297539 }}</ref><ref name=Mitz&Wise>{{cite journal |author1=Mitz, A.R.  |author2=Wise, S.P.  | year=1987 | title=The somatotopic organization of the supplementary motor area: intracortical microstimulation mapping | journal=J. Neurosci. | volume=7 | pages=1010–1021 | pmid=3572473 | issue=4 | pmc=6568999 | doi=10.1523/JNEUROSCI.07-04-01010.1987}}</ref> The map of the body in SMA is therefore extensively overlapping. SMA projects directly to the spinal cord and may play some direct role in the control of movement.<ref name=He&etal>{{cite journal | author=He, S.Q., Dum, R.P. and Strick, P.L | year=1995 | title=Topographic organization of corticospinal projections from the frontal lobe: motor areas on the medial surface of the hemisphere | journal=J. Neurosci. | volume=15 | pages=3284–3306 | pmid=7538558 | issue=5 Pt 1 | pmc=6578253 | doi=10.1523/JNEUROSCI.15-05-03284.1995}}</ref>

Based on early work using brain imaging techniques in the human brain, Roland<ref name=Roland&etal>{{cite journal | author=Roland, P.E., Larsen, B., Lassen, N.A. and Skinhoj, E | year=1980 | title=Supplementary motor area and other cortical areas in organization of voluntary movements in man | journal=J. Neurophysiol. | volume=43 | pages=118–136 | pmid=7351547 | issue=1 | doi=10.1152/jn.1980.43.1.118}}</ref> suggested that the SMA was especially active during the internally generated plan to make a sequence of movements. In the monkey brain, neurons in the SMA are active in association with specific learned sequences of movement.<ref name=Halsband&etal>{{cite journal | author=Halsband, U., Matsuzaka, Y. and Tanji, J. | year=1994 | title=Neuronal activity in the primate supplementary, pre-supplementary and premotor cortex during externally and internally instructed sequential movements | journal=Neurosci. Res. | volume=20 | pages=149–155 | doi=10.1016/0168-0102(94)90032-9 | pmid=7808697 | issue=2| s2cid=5930996 }}</ref>

Others have suggested that, because the SMA appears to control movement bilaterally, it may play a role in inter-manual coordination.<ref name=Brinkman>{{cite journal | author=Brinkman, C | year=1981 | title=Lesions in supplementary motor area interfere with a monkey's performance of a bimanual coordination task | journal=Neurosci. Lett. | volume=27 | pages=267–270 | doi=10.1016/0304-3940(81)90441-9 | pmid=7329632 | issue=3| s2cid=41060226 }}</ref>

Yet others have suggested that, because of the direct projection of SMA to the spinal cord and because of its activity during simple movements, it may play a direct role in motor control rather than solely a high level role in planning sequences.<ref name=He&etal/><ref name=Picard&Strick>{{cite journal |author1=Picard, N.  |author2=Strick, P.L  | title=Activation of the supplementary motor area (SMA) during performance of visually guided movements | journal=Cereb. Cortex | volume=13 | pages=977–986 | doi=10.1093/cercor/13.9.977 | pmid=12902397 | year=2003 | issue=9| doi-access=free }}</ref>

On the basis of the movements evoked during electrical stimulation, it has been suggested that the SMA may have evolved in primates as a specialist in the part of the motor repertoire involving climbing and other complex locomotion.<ref name=Graziano&2008/><ref name=Graziano&Aflalo&Cooke>{{cite journal | author=[[Michael Graziano|Graziano, M.S.A.]], Aflalo, T.N. and Cooke, D.F | year=2005 | title=Arm movements evoked by electrical stimulation in the motor cortex of monkeys | journal=J. Neurophysiol. | volume=94 | pages=4209–4223 | doi=10.1152/jn.01303.2004 | pmid=16120657 | issue=6}}</ref>

Based on the pattern of projections to the spinal cord, it has been suggested that another set of motor areas may lie next to the supplementary motor area, on the medial (or midline) wall of the hemisphere.<ref name=He&etal/> These medial areas are termed the cingulate motor areas. Their functions are not yet understood.