Transcript Group 8: Autism and Mirron Neurons

Autism And Mirror
Neurons
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Autism Spectrum Disorder
(ASD)
Affected people exhibit a wide range
in the magnitude in their symptoms
These patients show deficits in:
•
Communication and Socialization
•
Theory of Mind
•
Empathy
Is a dysfunctional mirror neuron system
responsible for this phenotype?
•
Mirror Neuron
(MNs)
• First discovered in Macaque
monkeys found to:
• Mediate imitation
• Basis of action understanding
Associates observed actions with
motor representations of that
action
Mirror Neurons and Autism
•
•
•
•
Mu rhythm desynchronizes during observed
movement and own movement
Control participants showed Mu rhythm
suppression when observing and performing
action
ASD participants had same suppression when
performing action, but very little or no
suppression when observing same action
This proposes a deficit in Mirror neuron
activity in ASD
Mirror Neurons Localized
to Broca’s Area
• Goldin-Meadow, 1999) Localized a population of
mirror neurons in the F5 region of the Macaque
brain that were active during the presentation of a
communicative mouth gesture
•
-(Buccino et al., 2004) Found communicative
facial gestures also elicit mirror neuron activity in
the human Broca’s Area
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Mirror Neurons Involved in Language
Processing in Motor Cortex
• -(Hauk, 2004) with fMRI, found that when
subjects would read passages concerning various
body features(face, hands etc.) there would be
corresponding activity in the related motor cortex
regions.
•
-(Fadiga, 2002) Presented subjects with
phonemes and found motor cortex activity at areas
concerned with tongue manipulation during
speech.
Theory of Mind
2 Models
“Theory Theory”
•
observing patterned behaviors in others allows
humans to develop theories to explain and predict
mental states
“Simulation Theory”
•
brain simulates the mental processes of others:
“putting themselves in the other’s shoes”
• Mirror neurons thought to play a role in ToM
Imitation, ToM, and
Autism
Imitation thought to play a role in
theory of mind
• MN activation allows others to
generate an executive plan like the
one being observed
• Mechanism seems to follow
simulation model
• Mirror Neuron Dysfunction can
account for social problems
Mirror Neurons and Empathy
Empathy: The ability to identify with the feelings,
thoughts, or mental states of other people (putting yourself
“in the shoes” of someone else)
Humans are normally able to do this quite well once fully
developed- BUT autistic people seem to have a lack of
empathy.
What allows us to interpret the feelings of other people?
Mirror Neurons!… along with a few other structures
One proposed pathway of emotional interpretation:
• Another person’s action is visually encoded by the
superior temporal cortex
• Mirror neurons in the posterior parietal cortex
interpret the movement
• Mirror neurons in the inferior frontal cortex infer the
goal or intent of the action
• Parts of the insula, which receive input from all three
cortical areas, project to the limbic system
• The limbic areas process emotionally relevant content
• Meanwhile, the mirror neurons also project back to the
superior temporal cortex to allow imitation
The Insula
Bridge Between Action Representation and Emotion
Mirror Neurons and Empathy
Dapretto et al (2006): fMRI recordings for the observation
and imitation of various emotional expressions
Autistic children had:
• MORE activity in the right visual and left anterior
parietal areas (visual and motor attention)
• LESS activity in the insula and amygdala (emotion)
• NO activity in the mirror neuron system of the
inferior frontal gyrus
Mirror Neurons and Consciousness
Mirror neurons probably play a huge role in many aspects of
our conscious state, particularly involving interaction with
other people (language, theory of mind, empathy)
Are these abilities crucial to our consciousness? Does the lack
of them (as in autism, at least to some extent) alter the way
we experience the world?
Bibliography
Buccino et al. “Neural circuits involved in the recognition of actions performed by nonconspecifics: an fMRI study” Journal of Cognitive
Neuroscience 16(2004): 114-26.
Carr, L, M Iacoboni, MC Dubeau, JC Mazziotta, GL Lenzi. “Neural mechanisms of empathy in humans: A relay from neural systems for
imitation to limbic areas.” Proceedings of the National Academy of Sciences 100 (2003): 5497-5502.
<http://www.pnas.org/cgi/content/full/100/9/5497>. 31 May 2007.
Dapretto, M, MS Davies, JH Pfeifer, AA Scott, M Sigman, SY Bookheimer & M Iacoboni. “Understanding emotions in others: mirror neuron
dysfunction in children with autism spectrum disorders.” Nature Neuroscience 9 (2006): 28-30.
<http://chd.ucsd.edu/articles05_06/Dapretto06.pdf>.15 May 2007
Dupont S, V Bouilleret, D Hasboun, F Semah, M Baulac. “Functional anatomy of the insula: new insights from imaging.” Surgical and
Radiological Anatomy 25 (2003): 113-119. <http://people.hnl.bcm.tmc.edu/jli/reference/41.pdf>. 31 May 2007.
Fadiga et al. “Speech listening specifically modulates the excitability of tongue muscles” European Journal of Neuroscience 15(2002):399-402.
Goldin-Meadow. “The role of gestures in communication and thinking” Trends in Cognition 3(1999):419-29.
Hauk et al. “Neurophysiological distinction of action words in the fronto-central cortex” Human Brain Mapping 21(2004): 191-201.
Preston SD and FMB de Waal. “Empathy: Its ultimate and proximate bases.” Behavioral and Brain Sciences 25 (2002): 1-20.
<http://peacecenter.berkeley.edu/BBS_PrestondeWaal.pdf>. 15 May 2007.
Oberman LM, Hubbard EM, McCleery JP, Altschuler EL, Ramachandran VS, Pineda JA., EEG evidence for mirror neuron dysfunction in autism
spectral disorders, Brain Res Cogn Brain Res.; 24(2):190-8, 2005-06
Rizzolatti G., Craighero L., The mirror-neuron system, Annual Review of Neuroscience. 2004;27:169-92
Terje Falck-Ytter, Gustaf Gredebäck & Claes von Hofsten, Infants predict other people's action goals, Nature Neuroscience 9 (2006)
Elisabeth L. Hill; Uta FrithPhilosophical Transactions: Biological Sciences, Vol. 358, No. 1430, Autism: Mind and Brain. (Feb. 28,
2003), pp. 281-289.