Motor cortex is the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements.
Components of the motor cortex 
The motor cortex can be divided into several main parts:
- the primary motor cortex is the main contributor to generating neural impulses that pass down to the spinal cord and control the execution of movement. However, some of the other motor cortical fields also play a role in this function.
- the premotor cortex is responsible for some aspects of motor control, possibly including the preparation for movement, the sensory guidance of movement, the spatial guidance of reaching, or the direct control of some movements with an emphasis on control of proximal and trunk muscles of the body.
- the supplementary motor area (or SMA), has many proposed functions including the internally generated planning of movement, the planning of sequences of movement, and the coordination of the two sides of the body such as in bi-manual coordination.
- The posterior parietal cortex is sometimes also considered to be part of the group of motor cortical areas. It is thought to be responsible for transforming multisensory information into motor commands, and to be responsible for some aspects of motor planning, in addition to many other functions that may not be motor related.
- The primary somatosensory cortex, especially the part called area 3a, which lies directly against the motor cortex, is sometimes considered to be functionally part of the motor control circuitry.
Other brain regions outside the cerebral cortex are also of great importance to motor function, most notably the cerebellum, the basal ganglia, and the red nucleus, as well as other subcortical motor nuclei.
Evolutionary aspects 
In the course of evolution a tendency to develop increasingly more complex brain structures and cortical densification can be observed. Cortical densification describes the increased shifting of control processes into the cerebral cortex. The motor cortex is a relatively recent development and occurs only in mammals. The execution of movement in fish, amphibians, reptiles and also birds is regulated by a core part of the brain called Archistriatum, in mammals the corresponding part of the brain is called Striatum, which is also involved in the execution of movement.
Especially primates have a highly developed motor cortex. In addition, separating them from all other mammals, they have many monosynaptic, thus direct connections from the motor cortex to the motor neurons in the brain stem and spinal cord. This leads to the conclusion that only primates have a conscious, planned and finely graduated movement of single muscles, whereas the execution of movement for most other animals is probably more automatic and without the possibility of deliberate interference. In comparison to primates, ungulates have a relatively weakly developed pyramidal tract, which ends in the neck region of the spinal cord (Intumescencia cervicalis) and plays an important part in the production of facial expressions. As for dogs, while about 30% of the pyramidal fibres reach the loin region of the spinal cord (Intumescencia lumbalis), those fibres always end on interneurons, never directly on anterior horn cells.
Consequently, a complete impairment of the motor cortex in one hemisphere of the brain never leads to hemiplegia in non-primates, but rather to contralateral disorders concerning postural reflexes. Over the course of their evolutionary process, humans developed considerable control over their hands and articulatory muscles. Furthermore, humans have a uniquely high potential to learn new sequences of movement throughout their life.
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Early work on the motor cortex 
A little later, in 1874, David Ferrier, working in the laboratory of the West Riding Lunatic Asylum at Wakefield (at the invitation of its director, James Crichton-Browne), mapped the motor cortex in the monkey brain using electrical stimulation. He found that the motor cortex contained a rough map of the body with the feet at the top (or dorsal part) of the brain and the face at the bottom (or ventral part) of the brain. He also found that when electrical stimulation was maintained for a longer time, such as for a second, instead of being discharged over a fraction of a second, then some coordinated, seemingly meaningful movements could be caused, instead of only muscle twitches.
One of the first detailed maps of the human motor cortex was described in 1905 by Campbell. He did autopsies on the brains of amputees. A person who had lost an arm would over time apparently lose some of the neuronal mass in the part of the motor cortex that normally controls the arm. Likewise, a person who had lost a leg would show degeneration in the leg part of motor cortex. In this way the motor map could be established. In the period between 1919 and 1936 others mapped the motor cortex in detail using electrical stimulation, including the husband and wife team Vogt and Vogt, and the neurosurgeon Foerster.
Perhaps the best-known experiments on the human motor map were published by Penfield in 1937. Using a procedure that was common in the 1930s, he examined epileptic patients who were undergoing brain surgery. These patients were given a local anesthetic, their skulls were opened, and their brains exposed. Then, electrical stimulation was applied to the surface of the brain to map out the speech areas. In this way, the surgeon would be able to avoid any damage to speech circuitry. The brain focus of the epilepsy could then be surgically removed. During this procedure, Penfield mapped the effect of electrical stimulation in all parts of the cerebral cortex, including motor cortex.
Penfield is sometimes mistakenly considered to be the discoverer of the map in motor cortex. It was discovered approximately 70 years before his work. However, Penfield drew a picture of a little man stretched over the cortical surface and used the term "homunculus" to refer to it. Perhaps for these reasons his work has become iconic in neuroscience.
The motor cortex map 
A simple view, that is almost certainly too limited and that dates back to the earliest work on the motor cortex, is that neurons in motor cortex control movement by a feed-forward direct pathway. In that view, a neuron in motor cortex sends an axon or projection to the spinal cord and forms a synapse on a motoneuron. The motoneuron sends an axon to a muscle. When the neuron in cortex becomes active, it causes a muscle contraction. The greater the activity in motor cortex, the stronger the muscle force. Each point in motor cortex controls a muscle or a small group of related muscles. This description is only partly correct.
Most neurons in the motor cortex that project to the spinal cord synapse on interneuron circuitry in the spinal cord, not directly onto motoneurons. One suggestion is that the direct, cortico-motoneuronal projections are a specialization that allows for the fine control of the fingers.
The view that each point in motor cortex controls a muscle or a limited set of related muscles was debated over the entire history of research on the motor cortex, and was suggested in its strongest and most extreme form by Asanuma on the basis of experiments in cats and monkeys using electrical stimulation. However, almost every other experiment to examine the map, including the classic work of Ferrier and of Penfield showed that each point in motor cortex influences a range of muscles and joints. The map is greatly overlapping. The overlap in the map is generally greater in the premotor cortex and supplementary motor cortex, but even the map in the primary motor cortex controls muscles in an extensively overlapped manner. Many studies have demonstrated the overlapping representation of muscles in the motor cortex.
The clearest example of the coordination of muscles into complex movement in the motor cortex comes from the work of Graziano and colleagues on the monkey brain. They used electrical stimulation on a behavioral time scale, such as for half a second instead of the more typical hundredth of a second. They found that this type of stimulation of the monkey motor cortex often evoked complex, meaningful actions. For example, stimulation of one site in cortex would cause the hand to close, move to the mouth, and the mouth to open. Stimulation of another site would cause the hand to open, rotate until the grip faced outward, and the arm to project out as if the animal were reaching. Different complex movements were evoked from different sites and these movements were mapped in the same orderly manner in all monkeys tested. Computational models showed that the normal movement repertoire of a monkey, if arranged on a sheet such that similar movements are placed near each other, will result in a map that matches the actual map found in the monkey motor cortex. This work suggests that the motor cortex does not truly contain a homunculus-type map of the body. Instead, the deeper principle may be a rendering of the movement repertoire onto the cortical surface. To the extent that the movement repertoire breaks down partly into the actions of separate body parts, the map contains a rough and overlapping body arrangement noted by researchers over the past century.
Movement coding in the primary motor cortex 
Evarts suggested that each neuron in the motor cortex contributes to the force in a muscle. As the neuron becomes active, it sends a signal to the spinal cord, the signal is relayed to a motoneuron, the motoneuron sends a signal to a muscle, and the muscle contracts. The more activity in the motor cortex neuron, the more muscle force.
Georgopoulos and colleagues suggested that muscle force alone was too simple a description. They trained monkeys to reach in various directions and monitored the activity of neurons in the motor cortex. They found that each neuron in the motor cortex was maximally active during a specific direction of reach, and responded less well to neighboring directions of reach. On this basis they suggested that neurons in motor cortex, by "voting" or pooling their influences into a "population code", could precisely specify a direction of reach.
The proposal that motor cortex neurons encode the direction of a reach became controversial. Scott and Kalaska showed that each motor cortex neuron was better correlated with the details of joint movement and muscle force than with the direction of the reach. Schwartz and colleagues showed that motor cortex neurons were well correlated with the speed of the hand. Strick and colleagues found that some neurons in motor cortex were active in association with muscle force and some with the spatial direction of movement. Todorov proposed that the many different correlations are the result of a muscle controller in which many movement parameters happen to be correlated with muscle force.
The code by which neurons in the primate motor cortex control the spinal cord, and thus movement, remains debated.
Some specific progress in understanding how motor cortex causes movement has also been made in the rodent model. The rodent motor cortex, like the monkey motor cortex, may contain subregions that emphasize different common types of actions. For example, one region appears to emphasize the rhythmic control of whisking. Neurons in this region project to a specific subcortical nucleus in which a pattern generator coordinates the cyclic rhythm of the whiskers. This nucleus then projects to the muscles that control the whiskers.
The premotor cortex 
In the earliest work on the motor cortex, researchers recognized only one cortical field involved in motor control. Campbell was the first to suggest that there might be two fields, a "primary" motor cortex and an "intermediate precentral" motor cortex. His reasons were largely based on cytoarchitectonics, or the study of the appearance of the cortex under a microscope. The primary motor cortex contains cells with giant cell bodies known as "Betz cells". These cells were mistakenly thought to be the main outputs from the cortex, sending fibers to the spinal cord. It has since been found that Betz cells account for about 2-3% of the projections from the cortex to the spinal cord, or about 10% of the projections from the primary motor cortex to the spinal cord. The specific function of the Betz cells that distinguishes them from other output cells of the motor cortex remains unknown, but they continue to be used as a marker for the primary motor cortex.
Other researchers, such as Vogt and Vogt and Foerster also suggested that motor cortex was divided into a primary motor cortex (area 4, according to Brodmann's naming scheme) and a higher-order motor cortex (area 6 according to Brodmann).
Penfield notably disagreed and suggested that there was no functional distinction between area 4 and area 6. In his view both were part of the same map, though area 6 tended to emphasize the muscles of the back and neck. Woolsey who studied the motor map in monkeys also believed there was no distinction between primary motor and premotor. M1 was the name for the proposed single map that encompassed both the primary motor cortex and the premotor cortex. Although sometimes "M1" and "primary motor cortex" are used interchangeably, strictly speaking, they derive from different conceptions of motor cortex organization.
Despite the views of Penfield and Woolsey, a consensus emerged that area 4 and area 6 had sufficiently different functions that they could be considered different cortical fields. Fulton ] helped to solidify this distinction between a primary motor cortex in area 4 and a premotor cortex in area 6. As Fulton pointed out, and as all subsequent research has confirmed, both primary motor and premotor cortex project directly to the spinal cord and are capable of some direct control of movement. Fulton showed that when the primary motor cortex is damaged in an experimental animal, movement soon recovers; when the premotor cortex is damaged, movement soon recovers; when both are damaged, movement is lost and the animal cannot recover.
The premotor cortex is now generally divided into four sections. First it is divided into an upper (or dorsal) premotor cortex and a lower (or ventral) premotor cortex. Each of these is further divided into a region more toward the front of the brain (rostral premotor cortex) and a region more toward the back (caudal premotor cortex). A set of acronyms are commonly used: PMDr (premotor dorsal, rostral), PMDc, PMVr, PMVc. Some researchers use a different terminology. Field 7 or F7 denotes PMDr; F2 = PMDc; F5=PMVr; F4=PMVc.
PMVc or F4 is often studied with respect to its role in the sensory guidance of movement. Neurons here are responsive to tactile stimuli, visual stimuli, and auditory stimuli. These neurons are especially sensitive to objects in the space immediately surrounding the body, in so-called peripersonal space. Electrical stimulation of these neurons causes an apparent defensive movement as if protecting the body surface. This premotor region may be part of a larger circuit for maintaining a margin of safety around the body and guiding movement with respect to nearby objects.
PMVr or F5 is often studied with respect to its role in shaping the hand during grasping and in interactions between the hand and the mouth. Mirror neurons were first discovered in area F5 in the monkey brain by Rizzolatti and colleagues. These neurons are active when the monkey grasps an object. Yet the same neurons become active when the monkey watches an experimenter grasp an object in the same way. The neurons are therefore both sensory and motor. Mirror neurons are proposed to be a basis for understanding the actions of others by internally imitating the actions using one's own motor control circuits.
The supplementary motor cortex 
Penfield 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. 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.
Based on early work using brain imaging techniques in the human brain, Roland 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.
Others have suggested that, because the SMA appears to control movement bilaterally, it may play a role in inter-manual coordination.
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.
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.
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. These medial areas are termed the cingulate motor areas. Their functions are not yet understood.
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- Fritsch, G and Hitzig, E (1870). "Über die elektrische Erregbarkeit des Grosshirns". Arch. f. Anatomische, Physiologische, und Wissenschaftliche Medizin: 300–332. Translated in: von Bonin, G., ed. (1960). Some Papers on the Cerebral Cortex. Springfield IL: Charles Thomas. pp. 73–96.
- Ferrier, D (1874). "Experiments on the brain of monkeys - No. 1". Proc. R. Soc. Lond 23 (156–163): 409–430. doi:10.1098/rspl.1874.0058.
- Beevor, C. and Horsley, V (1887). "A minute analysis (experimental) of the various movements produced by stimulating in the monkey different regions of the cortical centre for the upper limb, as defined by Professor Ferrier". Phil. Trans. R. Soc. Lond. B 178: 153–167. doi:10.1098/rstb.1887.0006.
- Grunbaum A. and Sherrington, C (1901). "Observations on the physiology of the cerebral cortex of some of the higher apes. (Preliminary communication)". Proc. R. Soc. Lond 69 (451–458): 206–209. doi:10.1098/rspl.1901.0100.
- Campbell, A. W. (1905). Histological Studies on the Localization of Cerebral Function. Cambridge, MA: Cambridge University Press. OCLC 6687137.
- Vogt, C. and Vogt, O. (1919). "Ergebnisse unserer Hirnforschung". Journal für Psychologie und Neurologie 25: 277–462.
- Foerster, O (1936). "The motor cortex of man in the light of Hughlings Jackson's doctrines". Brain 59 (2): 135–159. doi:10.1093/brain/59.2.135.
- Penfield, W. and Boldrey, E. (1937). "Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation". Brain 60 (4): 389–443. doi:10.1093/brain/60.4.389.
- Penfield, W. (1959). "The interpretive cortex". Science 129 (3365): 1719–1725. doi:10.1126/science.129.3365.1719. PMID 13668523.
- Bortoff, G.A. and Strick, P.L. (1993). "Corticospinal terminations in two new-world primates: further evidence that corticomotoneuronal connections provide part of the neural substrate for manual dexterity". J.Neurosci 13 (12): 5105–5118. PMID 7504721.
- Heffner, R. and Masterton, B. (1975). "Variation in form of the pyramidal tract and its relationship to digital dexterity". Brain Behav. Evol 12 (3): 161–200. doi:10.1159/000124401. PMID 1212616.
- Asanuma, H. (1975). "Recent developments in the study of the columnar arrangement of neurons within the motor cortex". Physiol. Rev 55 (2): 143–156. PMID 806927.
- Cheney, P.D. and Fetz, E.E. (1985). "Comparable patterns of muscle facilitation evoked by individual corticomotoneuronal (CM) cells and by single intracortical microstimuli in primates: evidence for functional groups of CM cells". J.Neurophysiol 53 (3): 786–804. PMID 2984354.
- Schieber, M.H. and Hibbard, L.S. (1993). "How somatotopic is the motor cortex hand area?". Science 261 (5120): 489–492. doi:10.1126/science.8332915. PMID 8332915.
- Rathelot, J.A. and Strick, P.L. (2006). "Muscle representation in the macaque motor cortex: an anatomical perspective". Proc. Natl. Acad. Sci. USA 103 (21): 8257–8262. doi:10.1073/pnas.0602933103. PMC 1461407. PMID 16702556.
- Park, M.C., Belhaj-Saif, A., Gordon, M. and Cheney, P.D. (2001). "Consistent features in the forelimb representation of primary motor cortex in rhesus macaques". J. Neurosci 21 (8): 2784–2792. PMID 11306630.
- Sanes, J.N., Donoghue, J.P., Thangaraj, V., Edelman, R.R. and Warach, S. (1995). "Shared neural substrates controlling hand movements in human motor cortex". Science 268 (5218): 1775–1777. doi:10.1126/science.7792606. PMID 7792606.
- Donoghue, J.P., Leibovic, S. and Sanes, J.N. (1992). "Organization of the forelimb area in squirrel monkey motor cortex: representation of digit, wrist and elbow muscles". Exp. Brain Res 89: 1–10.
- Meier, J.D., Aflalo, T.N., Kastner, S. and Graziano, M.S.A. (2008). "Complex organization of human primary motor cortex: A high-resolution fMRI study". J. Neurophysiol 100 (4): 1800–1812. doi:10.1152/jn.90531.2008. PMC 2576195. PMID 18684903.
- Nudo, R.J., Milliken, G.W., Jenkins, W.M. and Merzenich, M.M. (1996). "Use-dependent alterations of movement representations in primary motor cortex of adult squirrel monkeys". J.Neurosci 16 (2): 785–807. PMID 8551360.
- Martin, J.H., Engber, D. and Meng, Z. (2005). "Effect of forelimb use on postnatal development of the forelimb motor representation in primary motor cortex of the cat". J.Neurophysiol 93 (5): 2822–2831. doi:10.1152/jn.01060.2004. PMID 15574795.
- Graziano, M.S.A., Taylor, C.S.R. and Moore, T. (2002). "Complex movements evoked by microstimulation of precentral cortex". Neuron 34 (5): 841–851. doi:10.1016/S0896-6273(02)00698-0. PMID 12062029.
- Graziano, M.S.A. (2008). The Intelligent Movement Machine. Oxford, UK: Oxford University Press.
- Graziano, M.S.A. and Aflalo, T.N. (2007). "Mapping behavioral repertoire onto the cortex". Neuron 56 (2): 239–251. doi:10.1016/j.neuron.2007.09.013. PMID 17964243.
- Stepniewska, I., Fang, P.C. and Kaas, J.H. (2005). "Microstimulation reveals specialized subregions for different complex movements in posterior parietal cortex of prosimian galagos". Proc. Natl. Acad. Sci. USA 102 (13): 4878–4883. doi:10.1073/pnas.0501048102. PMC 555725. PMID 15772167.
- Gharbawie, O.A., Stepniewska, I., Qi, H. and Kaas, J.H. (2011). "Multiple parietal-frontal pathways mediate grasping in macaque monkeys". J. Neurosci 31 (32): 11660–11677. doi:10.1523/JNEUROSCI.1777-11.2011. PMC 3166522. PMID 21832196.
- Haiss, F. and Schwarz, C (2005). "Spatial segregation of different modes of movement control in the whisker representation of rat primary motor cortex". J. Neurosci 25 (6): 1579–1587. doi:10.1523/JNEUROSCI.3760-04.2005. PMID 15703412.
- Ramanathan, D., Conner, J.M. and Tuszynski, M.H. (2006). "A form of motor cortical plasticity that correlates with recovery of function after brain injury". Proc. Natl. Acad. Sci. USA 103 (30): 11370–11375. doi:10.1073/pnas.0601065103. PMC 1544093. PMID 16837575.
- Evarts, E.V. (1968). "Relation of pyramidal tract activity to force exerted during voluntary movement". J. Neurophysiol 31 (1): 14–27. PMID 4966614.
- Georgopoulos, A.P., Kalaska, J.F., Caminiti, R. and Massey, J.T. (1982). "On the relations between the direction of two-dimensional arm movements and cell discharge in primate motor cortex". J. Neurosci 2 (11): 1527–1537. PMID 7143039.
- Georgopoulos A.P., Kettner, R.E. and Schwartz, A.B. (1988). "Primate motor cortex and free arm movements to visual targets in three-dimensional space. II. Coding of the direction of movement by a neuronal population". J. Neurosci 8 (8): 2928–2937. PMID 3411362.
- Georgopoulos A.P., Schwartz, A.B. and Kettner, R.E. (1986). "Neuronal population coding of movement direction". Science 233 (4771): 1416–1419. doi:10.1126/science.3749885. PMID 3749885.
- Scott, S.H. and Kalaska, J.F. (1995). "Changes in motor cortex activity during reaching movements with similar hand paths but different arm postures". J. Neurophysiol 73 (6): 2563–2567. PMID 7666162.
- Moran, D.W. and Schwartz, A.B. (1999). "Motor cortical representation of speed and direction during reaching". J. Neurophysiol 82 (5): 2676–2692. PMID 10561437.
- Kakei, S., Hoffman, D. and Strick, P (1999). "Muscle and movemet representations in the primary motor cortex". Science 285 (5436): 2136–2139. doi:10.1126/science.285.5436.2136. PMID 10497133.
- Todorov, E (2000). "Direct cortical control of muscle activation in voluntary arm movements: a model". Nat Neurosci 3 (4): 391–398. doi:10.1038/73964. PMID 10725930.
- Brecht, M., Schneider, M., Sakmann, B. and Margrie, T.W. (2004). "Whisker movements evoked by stimulation of single pyramidal cells in rat motor cortex". Nature 427 (6976): 704–710. doi:10.1038/nature02266. PMID 14973477.
- Cramer, N.P. and Keller, A (2006). "Cortical control of a whisking central pattern generator". J. Neurophysiol 96 (1): 209–217. doi:10.1152/jn.00071.2006. PMC 1764853. PMID 16641387.
- Rivara CB, Sherwood CC, Bouras C, and Hof PR (2003). "Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex". The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology 270 (2): 137–151. doi:10.1002/ar.a.10015. PMID 12524689.
- Lassek, A.M. (1941). "The pyramidal tract of the monkey". J. Comp. Neurol 74 (2): 193–202. doi:10.1002/cne.900740202.
- Brodmann, K (1909). Vergleichende Lokalisationslehre der Grosshirnrinde. Leipzig: J.A. Barth.
- Woolsey, C.N., Settlage, P.H., Meyer, D.R., Sencer, W., Hamuy, T.P. and Travis, A.M. (1952). "Pattern of localization in precentral and "supplementary" motor areas and their relation to the concept of a premotor area". Association for Research in Nervous and Mental Disease, Vol. 30 (New York, NY: Raven Press): 238–264.
- Fulton, J (1935). "A note on the definition of the "motor" and "premotor" areas". Brain 58 (2): 311–316. doi:10.1093/brain/58.2.311.
- Matelli, M., Luppino, G. and Rizzolati, G (1985). "Patterns of cytochrome oxidase activity in the frontal agranular cortex of the macaque monkey". Behav. Brain Res 18 (2): 125–136. doi:10.1016/0166-4328(85)90068-3. PMID 3006721.
- Preuss, T.M., Stepniewska, I. and Kaas, J.H (1996). "Movement representation in the dorsal and ventral premotor areas of owl monkeys: a microstimulation study". J. Comp. Neurol 371 (4): 649–676. doi:10.1002/(SICI)1096-9861(19960805)371:4<649::AID-CNE12>3.0.CO;2-E. PMID 8841916.
- Hochermann, S. and Wise, S.P (1991). "Effects of hand movement path on motor cortical activity in awake, behaving rhesus monkeys". Exp. Brain Res 83 (2): 285–302. PMID 2022240.
- Cisik, P and Kalaska, J.F (2005). "Neural correlates of reaching decisions in dorsal premotor cortex: specification of multiple direction choices and final selection of action". Neuron 45 (5): 801–814. doi:10.1016/j.neuron.2005.01.027. PMID 15748854.
- Churchland, M.M., Yu, B.M., Ryu, S.I., Santhanam, G. and Shenoy, K.V (2006). "Neural variability in premotor cortex provides a signature of motor preparation". J. Neurosc 26 (14): 3697–3712. doi:10.1523/JNEUROSCI.3762-05.2006.
- Weinrich, M., Wise, S.P. and Mauritz, K.H (1984). "A neurophyiological study of the premotor cortex in the rhesus monkey". Brain 107 (2): 385–414. doi:10.1093/brain/107.2.385. PMID 6722510.
- Brasted, P.J. and Wise, S.P (2004). "Comparison of learning-related neuronal activity in the dorsal premotor cortex and striatum". European J. Neurosci 19 (3): 721–740. doi:10.1111/j.0953-816X.2003.03181.x.
- Muhammad, R., Wallis, J.D. and Miller, E.K (2006). "A comparison of abstract rules in the prefrontal cortex, premotor cortex, inferior temporal cortex, and striatum". J. Cog. Neurosci 18 (6): 974–989. doi:10.1162/jocn.2006.18.6.974.
- Rizzolatti, G., Scandolara, C., Matelli, M. and Gentilucci, J (1981). "Afferent properties of periarcuate neurons in macaque monkeys, II. Visual responses". Beh. Brain Res 2 (2): 147–163. doi:10.1016/0166-4328(81)90053-X.
- Fogassi, L., Gallese, V., Fadiga, L., Luppino, G., Matelli, M. and Rizzolatti, G (1996). "Coding of peripersonal space in inferior premotor cortex (area F4)". J. Neurophysiol 76 (1): 141–157. PMID 8836215.
- Graziano, M.S.A., Yap, G.S. and Gross, C.G (1994). "Coding of visual space by premotor neurons". Science 266 (5187): 1054–1057. doi:10.1126/science.7973661. PMID 7973661.
- Graziano, M.S.A., Reiss, L.A. and Gross, C.G (1999). "A neuronal representation of the location of nearby sounds". Nature 397 (6718): 428–430. doi:10.1038/17115. PMID 9989407.
- Cooke, D.F. and Graziano, M.S.A (2004). "Super-flinchers and nerves of steel: Defensive movements altered by chemical manipulation of a cortical motor area". Neuron 43 (4): 585–593. doi:10.1016/j.neuron.2004.07.029. PMID 15312656.
- Graziano, M.S.A. and Cooke, D.F. (2006). "Parieto-frontal interactions, personal space, and defensive behavior". Neuropsychologia 44 (6): 845–859. doi:10.1016/j.neuropsychologia.2005.09.009. PMID 16277998.
- Rizzolatti, G., Camarda, R., Fogassi, L., Gentilucci, M., Luppino, G. and Matelli, M (1988). "Functional organization of inferior area 6 in the macaque monkey. II. Area F5 and the control of distal movements". Exp. Brain Res 71 (3): 491–507. PMID 3416965.
- Murata, A., Fadiga, L., Fogassi, L., Gallese, V. Raos, V and Rizzolatti, G (1997). "Object representation in the ventral premotor cortex (area F5) of the monkey". J. Neurophysiol 78: 2226–22230. PMID 9325390.
- di Pellegrino, G., Fadiga, L., Fogassi, L., Gallese, V. and Rizzolatti, G (1992). "Understanding motor events: a neurophysiological study". Exp. Brain Res 91 (1): 176–180. PMID 1301372.
- Rizzolatti, G. and Sinigaglia, C (2010). "The functional role of the parieto-frontal mirror circuit: interpretations and misinterpretations". Nat. Rev. Neurosci 11 (4): 264–274. doi:10.1038/nrn2805. PMID 20216547.
- Penfield, W. and Welch, K (1951). "The supplementary motor area of the cerebral cortex: A clinical and experimental study". Am. Med. Ass. Arch. Neurol. Psychiat. 66: 289–317. PMID 14867993.
- Gould, H.J. III, Cusick, C.G., Pons, T.P. and Kaas, J.H (1996). "The relationship of corpus callosum connections to electrical stimulation maps of motor, supplementary motor, and the frontal eye fields in owl monkeys". J. Comp. Neurol 247 (3): 297–325. doi:10.1002/cne.902470303. PMID 3722441.
- Luppino, G., Matelli, M., Camarda, R.M., Gallese, V. and Rizzolatti, G (1991). "Multiple representations of body movements in mesial area 6 and the adjacent cingulate cortex: an intracortical microstimulation study in the macaque monkey". J. Comp. Neurol 311 (4): 463–482. doi:10.1002/cne.903110403. PMID 1757598.
- Mitz, A.R. and Wise, S.P. (1987). "The somatotopic organization of the supplementary motor area: intracortical microstimulation mapping". J. Neurosci 7 (4): 1010–1021. PMID 3572473.
- He, S.Q., Dum, R.P. and Strick, P.L (1995). "Topographic organization of corticospinal projections from the frontal lobe: motor areas on the medial surface of the hemisphere". J. Neurosci 15 (5 Pt 1): 3284–3306. PMID 7538558.
- Roland, P.E., Larsen, B., Lassen, N.A. and Skinhoj, E (1980). "Supplementary motor area and other cortical areas in organization of voluntary movements in man". J. Neurophysiol 43 (1): 118–136. PMID 7351547.
- Halsband, U., Matsuzaka, Y. and Tanji, J. (1994). "Neuronal activity in the primate supplementary, pre-supplementary and premotor cortex during externally and internally instructed sequential movements". Neurosci. Res 20 (2): 149–155. doi:10.1016/0168-0102(94)90032-9. PMID 7808697.
- Brinkman, C (1981). "Lesions in supplementary motor area interfere with a monkey's performance of a bimanual coordination task". Neurosci. Lett 27 (3): 267–270. doi:10.1016/0304-3940(81)90441-9. PMID 7329632.
- Picard, N. and Strick, P.L (2003). "Activation of the supplementary motor area (SMA) during performance of visually guided movements". Cereb. Cortex 13 (9): 977–986. doi:10.1093/cercor/13.9.977. PMID 12902397.
- Graziano, M.S.A., Aflalo, T.N. and Cooke, D.F (2005). "Arm movements evoked by electrical stimulation in the motor cortex of monkeys". J. Neurophysiol 94 (6): 4209–4223. doi:10.1152/jn.01303.2004. PMID 16120657.
- Canavero S. Textbook of therapeutic cortical stimulation. New York: Nova Science, 2009