World Library  
Flag as Inappropriate
Email this Article

Michael Graziano

Article Id: WHEBN0025671719
Reproduction Date:

Title: Michael Graziano  
Author: World Heritage Encyclopedia
Language: English
Subject: Supplementary motor area, Aeon (digital magazine), Body schema, Motor cortex, Princeton University Department of Psychology
Collection: 1967 Births, American Male Writers, American Scientists, Living People
Publisher: World Heritage Encyclopedia

Michael Graziano

Michael Steven Anthony Graziano (born 1967) is an American scientist and novelist who is currently a professor of Psychology and Neuroscience at Princeton University.[1] His scientific research focuses on the brain basis of awareness. He has proposed the "attention schema" theory, an explanation of how, and for what adaptive advantage, brains attribute the property of awareness to themselves.[2][3] His previous work focused on how the cerebral cortex monitors the space around the body[4][5][6][7][8][9][10] and controls movement within that space.[11][12][13][14][15][16][17][18] Notably he has suggested that the classical map of the body in motor cortex, the homunculus, is not correct and is better described as a map of complex actions that make up the behavioral repertoire.[19] His publications on this topic have had a widespread impact among neuroscientists but have also generated controversy.[20][21][22][23][24][25][26][27] His novels[28][29] rely partly on his background in psychology and are known for surrealism or magic realism.[30][31][32] Graziano also composes music including symphonies[33] and string quartets.[34]


  • Biography 1
  • Contributions in neuroscience 2
  • Peripersonal space 3
  • An action map in the motor cortex 4
  • The brain basis of consciousness 5
  • Books 6
  • References 7


Graziano was born in Bridgeport Connecticut in 1967 and spent his childhood in Buffalo, New York. He received his Bachelor of Arts degree from Princeton University in 1989 in Psychology. He attended graduate school in neuroscience at MIT from 1989 to 1991 and then returned to Princeton University to complete his doctoral degree in 1996, in Neuroscience and Psychology. He remained at Princeton University as a postdoctoral researcher and then as a professor of neuroscience and psychology.

Contributions in neuroscience

Graziano has made contributions in three areas of neuroscience: how neurons in the primate brain encode peripersonal space, how the motor cortex controls complex movement, and the possible neuronal basis of consciousness. These contributions are detailed in the following sections.

Peripersonal space

In the 1990s Graziano with Charles Gross described the properties of a set of multisensory neurons in the monkey brain. Building on the work of Hyvarinen and colleagues[35][36] and Rizzolatti and colleagues[37][38] Graziano and Gross described a network of brain areas that appeared to encode the space immediately surrounding the body.[6][7][8][9][10]

Multimodal neurons in the monkey brain that encode the space near the body. Each neuron responds to touching a specific part of the body called the neuron's tactile receptive field. The same neuron responds to visual stimuli in the space near the tactile receptive field. Two examples are depicted. From Graziano MSA and Gross CG (1998) Spatial maps for the control of movement. Current Opinion in Neurobiology, 8: 195 -201.

Each multisensory neuron responded to a touch within a specific "tactile receptive field" on the body surface. Each neuron also responded to a visual stimulus near or approaching the tactile receptive field. The "visual receptive field" was therefore a region of nearby space affixed to the relevant body part. Some neurons responded to sound sources near the tactile receptive field.[6] Some neurons also responded mnemonically, becoming active when a part of the body moved through space and approached the remembered location of an object in the dark.[7] The activity of these multisensory neurons therefore signaled the presence of an object near or touching a part of the body, regardless of whether the object was felt, seen, heard, or remembered.

Electrical stimulation of these multisensory neurons almost always evoked a complex, coordinated movement that resembled a flinching, blocking, or protecting action.[15][16][17][18] Chemical inhibition of these neurons produced a "nerves of steel" state in which defensive reactions were inhibited.[15] Chemical enhancement of these neurons produced a "super flincher" state in which any mild stimulus, such as an object gently moved toward the face, evoked a full-blown flinching reaction.[15]

In Graziano's interpretation,[39] these multisensory neurons form a specialized brain-wide network that encodes the space near the body, computes a margin of safety, and helps to coordinate movements in relation to nearby objects with an emphasis on withdrawal or blocking movements. A subtle level of activation might bias ongoing behavior to avoid collision, whereas a strong level of activation evidently causes an overt defensive action.

The neurons that encode peripersonal space may also provide a neuronal basis for the psychological phenomenon of personal space.[39] Personal space, described by Hall,[40] is the flexible bubble of space around each person that is protected from intrusion by other people.

The peripersonal neurons may also play a central role in the body schema[41] an internally computed model of the body first proposed to exist by Head and Holmes in 1911.[42]

An action map in the motor cortex

In the 2000s Graziano's lab obtained evidence suggesting that the motor cortex might not contain a simple map of the body's muscles as in classical descriptions such as Penfield's description of a motor homunculus.[43] Instead, the motor cortex may contain a mapping of coordinated, behaviorally useful actions that make up a typical movement repertoire.

In their initial experiments, Graziano and colleagues used electrical microstimulation on the motor cortex of monkeys.[14][18] Most previous protocols in the motor cortex used very brief stimulation, such as for a hundredth of a second. Graziano applied the stimulation for half a second each time, on a behaviorally relevant time scale, in order to match the typical duration of a monkey's reaching and grasping. The longer stimulation train in Graziano's experiments evoked complex movements that included many joints and that resembled movements from the animal's behavioral repertoire.

For example, stimulation of one site always caused the hand to close in a grip, the arm to bring the hand to the mouth, and the mouth to open. Stimulation of another site always caused the grip to open, the palm to face away from the body, and the arm to extend, as if the monkey were reaching to grasp an object. Other sites evoked other complex movements. The behavioral repertoire of the animal seemed to be rendered onto the cortical sheet.

This initial work became controversial because of the method of stimulation on a behavioral time scale. The method was not commonly used in the study of motor cortex[25] although it had been used in the study of other brain regions.[19] That controversy may have partially distracted from the other methods used to study the action map.[19] For example, computational models[11] show that when the complex movement repertoire of a monkey is arranged in a flattened map, with similar movements represented near each other, the map closely resembles the known arrangement of the monkey motor cortex.

In Graziano's proposal, many of the complexities of the motor cortex, such as its overlapping maps of the body and its multiple areas with somewhat different mixtures of properties, may be a result of representing the many parts of the movement repertoire each with its own specialized computational requirements. Graziano[19] suggests that the action-map view does not contradict the more traditional view of motor cortex as a set of fields with differing functions. Instead, the action map may help to explain why motor cortex is divided into functionally distinct fields and why the fields are arranged spatially as they are.

Other researchers have since found a similar, ethological organization to motor cortical regions in monkeys, prosimians, cats, and rats.[22][44][45][21][20]

The brain basis of consciousness

Since 2010 Graziano's lab has studied the brain basis of consciousness. Graziano[46][47] proposed that specialized machinery in the brain computes the feature of awareness and attributes it to other people in a social context. The same machinery, in that hypothesis, also attributes the feature of awareness to oneself. Damage to that machinery disrupts one's own awareness.

The proposed "attention schema theory" was motivated by two sets of previous findings.

First, certain regions of the cortex are recruited during social perception as people construct models of other people's minds.[48][49][50][51][52][53][54][55] These regions include, among other areas, the superior temporal sulcus (STS) and the temporoparietal junction (TPJ) bilaterally but with a strong emphasis on the right hemisphere.

Second, when these same regions of cortex are damaged, people suffer from a catastrophic disruption of their own awareness of events and objects around them. The clinical syndrome of hemispatial neglect, or loss of awareness of one side of space, is particularly profound after damage to the TPJ or STS in the right hemisphere.[56][57]

The conjunction of these two previous findings suggests that awareness is a computed feature constructed by an expert system in the brain. The feature of awareness can be attributed to other people in the context of social perception. It can also be attributed to oneself, in effect creating one's own awareness.

Why construct the feature of awareness and attribute it to other people? In order to understand and predict the behavior of other people, it is useful to monitor other people's attentional state. Attention is a data handling method by which some signals in the brain are enhanced at the expense of others. According to the attention schema theory,[47] when the brain computes that person X is aware of thing Y, it is in effect modeling the state in which person X is applying an attentional enhancement to signal Y. Awareness is an attention schema. In that theory, the same process can be applied to oneself. One's own awareness is a schematized model of one's own attention.


Graziano writes literary novels under his own name and children's novels under the pseudonym B. B. Wurge. His stated reason for the pseudonym is to ensure that children do not accidentally read the wrong category of book.[58] His novels have been praised for their originality, vividness, and surreal imagination.[30][31][32] His book for children, The Last Notebook of Leonardo, won the 2011 Moonbeam Award.

His books include:

Literary Novels:

The Love Song of Monkey (2008)
The Divine Farce (2009)
Death My Own Way (2012)

Children's Novels (written under the name B. B. Wurge):

Billy and the Birdfrogs (2008)
Squiggle (2009)
The Last Notebook of Leonardo (2010)

Books on Neuroscience:

The Intelligent Movement Machine (2008)
God, Soul, Mind, Brain (2010)
Consciousness and the Social Brain (2013)

Books of music:

Three Modern Symphonies (2011)
Symphonies 4, 5, and 6 (2012)
Five String Quartets (2012)


  1. ^ Princeton University, Department of Psychology, Faculty Information
  2. ^ Graziano, M. S. A. (2013). Consciousness and the Social Brain.  
  3. ^ Graziano, MSA; Kastner, S (2011). "Human consciousness and its relationship to social neuroscience: A novel hypothesis". Cognitive Neuroscience 2 (2): 98.  
  4. ^ Aflalo, TN; Graziano, MSA (2008). "Four dimensional spatial reasoning in humans". Journal of Experimental Psychology, Human Perception and Performance 34 (5): 1066–1077.  
  5. ^ Graziano, MSA; Cooke, DF; Taylor, CSR (2000). "Coding the location of the arm by sight". Science 290 (5497): 1782–1786.  
  6. ^ a b c Graziano, MSA; Reiss, LAJ; Gross, CG (1999). "A neuronal representation of the location of nearby sounds". Nature 397 (6718): 428–430.  
  7. ^ a b c Graziano, MSA; Hu, XT; Gross, CG (1997). "Coding the locations of objects in the dark". Science 277 (5323): 239–241.  
  8. ^ a b Graziano, MSA; Hu, XT; Gross, CG (1997). "Visuo-spatial properties of ventral premotor cortex". Journal of Neurophysiology 77 (5): 2268–2292.  
  9. ^ a b Graziano, MSA; Yap, GS; Gross, CG (1994). "Coding of visual space by pre-motor neurons". Science 266 (5187): 1054–1057.  
  10. ^ a b Graziano, MSA; Gross, CG (1993). "A bimodal map of space: somatosensory receptive fields in the macaque putamen with corresponding visual receptive fields". Experimental Brain Research 97 (1): 96–109.  
  11. ^ a b Graziano, MSA; Aflalo, TN (2007). "Mapping behavioral repertoire onto the cortex". Neuron 56 (2): 239–251.  
  12. ^ Aflalo, TN; Graziano, MSA (2007). "Relationship between unconstrained arm movement and single neuron firing in the macaque motor cortex". Journal of Neuroscience 27 (11): 2760–2780.  
  13. ^ Graziano, MSA (2006). "The organization of behavioral repertoire in motor cortex". Annual Review of Neuroscience 29: 105–134.  
  14. ^ a b Graziano, MSA; Aflalo, TN; Cooke, DF (2005). "Arm movements evoked by electrical stimulation in the motor cortex of monkeys". Journal of Neurophysiology 94 (6): 4209–4223.  
  15. ^ a b c d Cooke, DF; Graziano, MSA (2004). "Super-flinchers and nerves of steel: Defensive movements altered by chemical manipulation of a cortical motor area". Neuron 43 (4): 585–593.  
  16. ^ a b Cooke, DF; Graziano, MSA (2004). "Sensorimotor integration in the precentral gyrus: Polysensory neurons and defensive movements". Journal of Neurophysiology 91 (4): 1648–1660.  
  17. ^ a b Cooke, DF; Taylor, CSR; Moore, T; Graziano, MSA (2003). "Complex movements evoked by microstimulation of Area VIP". Proceedings of the National Academy of Science U.S.A. 100 (10): 6163–6168.  
  18. ^ a b c Graziano, MSA; Taylor, CSR; Moore, T (2002). "Complex movements evoked by microstimulation of precentral cortex". Neuron 34 (5): 841–851.  
  19. ^ a b c d Graziano, M. S. A. (2008). The Intelligent Movement Machine.  
  20. ^ a b Ethier, C; Brizzi, L; Darling, WG; Capaday, C (2006). "Linear summation of cat motor cortex outputs". Journal of Neuroscience 26 (20): 5574–5581.  
  21. ^ a b Ramanathan, D; Conner, JM; Tuszynski, MH (2006). "A form of motor cortical plasticity that correlates with recovery of function after brain injury". Proceedings of the National Academy of Science U.S.A. 103 (30): 11370–11375.  
  22. ^ a b Stepniewska, I; Fang, PC; Kaas, JH (2005). "Microstimulation reveals specialized subregions for different complex movements in posterior parietal cortex of prosimian galagos". Proceedings of the National Academy of Science U.S.A. 102 (13): 4878–4883.  
  23. ^ Helmuth, L (2002). "Redrawing the brain's map of the body". Science 296 (5573): 1587–1588.  
  24. ^ Krauzlis, RJ (2002). "Reaching for answers". Neuron 34 (5): 673–674.  
  25. ^ a b Strick, PL (2002). "Stimulating Research on Motor Cortex". Nature Neuroscience 5 (8): 714–715.  
  26. ^ Moore, T (2004). "Homeland defense begins in precentral cortex". Journal of Neurophysiology 91 (4): 1456.  
  27. ^ Shadmehr, R (2009). "The motor cortex re-imagined". Nature Neuroscience 12 (6): 667.  
  28. ^ Graziano, M. S. A. (2008). The Love Song of Monkey. Leapfrog Press.  
  29. ^ Graziano, M. S. A. (2009). The Divine Farce. Leapfrog Press.  
  30. ^ a b [1], book review from Oct. 18, 2009.
  31. ^ a b "book review from Sept. 14, 2009".  
  32. ^ a b "book review from Dec. 3, 2009". Barnstable Patriot. 2009-12-03. 
  33. ^ Graziano, MSA (2011). Three modern symphonies and five character sketches in full score. Teaticket, Massachusetts: Quercus Press.  
  34. ^
  35. ^ Hyvarinen, J. (1981). "Regional distribution of functions in parietal association area 7 of the monkey". Brain Research 206 (2): 287–303.  
  36. ^ Hyvarinen, J; Poranen, A (1974). "Function of the parietal associative area 7 as revealed from cellular discharges in alert monkeys". Brain 97 (4): 673–692.  
  37. ^ Rizzolatti, G; Scandolara, C; Matelli, M; Gentilucci, M. (1981). "Afferent properties of periarcuate neurons in macaque monkeys. II. Visual responses". Behavioural Brain Research 2 (2): 147–163.  
  38. ^ Fogassi, L; Gallese, V.; di Pellegrino, G; Fadiga, L; Gentilucci, M; Luppino, M; Pedotti, A; Rizzolatti, G (1992). "Space coding by premotor cortex". Experimental Brain Research 89 (3): 686–690.  
  39. ^ a b Graziano, MSA; Cooke, DF (2006). "Parieto-frontal interactions, personal space, and defensive behavior". Neuropsychologia 44 (6): 845–859.  
  40. ^ Hall, ET (1966). The Hidden Dimension. Garden City, New York:  
  41. ^ Graziano, MSA; Botvinick, MM (2002). "How the brain represents the body: insights from neurophysiology and psychology".  In: Prinz, W; Hommel, B (eds.). Common Mechanisms in Perception and Action. Attention and Performance. Oxford, UK:  
  42. ^ Head, H; Holmes, G (1911). "Sensory disturbances from cerebral lesions". Brain 34 (2–3): 102.  
  43. ^  
  44. ^ Gharbawie, OA; Stepniewska, I; Qi, H; Kaas, JH (2011). "Multiple parietal-frontal pathways mediate grasping in macaque monkeys". Journal of Neuroscience 31 (32): 11660–11677.  
  45. ^ Haiss, F; Schwartz, C (2005). "Spatial segregation of different modes of movement control in the whisker representation of rat primary motor cortex". Journal of Neuroscience 25 (6): 1579–1587.  
  46. ^ Graziano, MSA (2010). God, Soul, Mind, Brain: A Neuroscientist's Reflections on the Spirit World. Teaticket MA: Leapfrog Press.  
  47. ^ a b Graziano, MSA; Kastner, S (2011). "Human consciousness and its relationship to social neuroscience: A novel hypothesis". Cog Neurosci 2 (2): 98–113.  
  48. ^ Brunet, E; Sarfati, Y; Hardy-Baylé, MC; Decety, J (2000). "A PET investigation of the attribution of intentions with a nonverbal task". Neuroimage 11 (2): 157–166.  
  49. ^ Ciaramidaro, A; Adenzato, M; Enrici, I; Erk, S; Pia, L; Bara, BG; Walter, H (2007). "The intentional network: how the brain reads varieties of intentions". Neuropsychologia 45 (13): 3105–3113.  
  50. ^ Fletcher, PC; Happé, F; Frith, U; Baker, SC; Dolan, RJ; Frackowiak, RS; Frith, CD (1995). "Other minds in the brain: a functional imaging study of "theory of mind" in story comprehension". Cognition 57 (2): 109–128.  
  51. ^ Gallagher, HL; Happé, F; Brunswick, N; Fletcher, PC; Frith, U; Frith, CD (2000). "Reading the mind in cartoons and stories: an fMRI study of 'theory of mind' in verbal and nonverbal tasks". Neuropsychologia 38 (1): 11–21.  
  52. ^ Goel, V; Grafman, J; Sadato, N; Hallett, M (1995). "Modeling other minds". NeuroReport 6 (13): 1741–1746.  
  53. ^ Saxe, R; Kanwisher, N (2003). "People thinking about thinking people: fMRI investigations of theory of mind". Neuroimage 19 (4): 1835–1842.  
  54. ^ Saxe, R; Wexler, A (2005). "Making sense of another mind: the role of the right temporo-parietal junction". Neuropsychologia 43 (10): 1391–1399.  
  55. ^ Vogeley, K; Bussfeld, P; Newen, A; Herrmann, S; Happé, F; Falkai, P; Maier, W; Shah, NJ et al. (2001). "Mind reading: neural mechanisms of theory of mind and self-perspective". Neuroimage 14 (1 Pt 1): 170–81.  
  56. ^ Karnath, HO; Ferber, S; Himmelbach, M (2001). "Spatial awareness is a function of the temporal not the posterior parietal lobe". Nature 411 (6840): 950–953.  
  57. ^ Vallar, G; Perani, D (1986). "The anatomy of unilateral neglect after right-hemisphere stroke lesions. A clinical/CT-scan correlation study in man". Neuropsychologia 24 (5): 609–622.  
  58. ^ "Book Review". Princeton Packet. November 25, 2008. 
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.