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One of the most exciting events in neurosciences over the past few years has been the discovery of a mechanism that unifies action perception and action execution. The essence of this 'mirror' mechanism is as follows: whenever individuals observe an action being done by someone else, a set of neurons that code for that action is activated in the observers' motor system. Since the observers are aware of the outcome of their motor acts, they also understand what the other individual is doing without the need for intermediate cognitive mediation. In this Review, after discussing the most pertinent data concerning the mirror mechanism, we examine the clinical relevance of this mechanism. We first discuss the relationship between mirror mechanism impairment and some core symptoms of autism. We then outline the theoretical principles of neurorehabilitation strategies based on the mirror mechanism. We conclude by examining the relationship between the mirror mechanism and some features of the environmental dependency syndromes.
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Mirror neurons and their clinical relevance
Giacomo Rizzolatti*, Maddalena Fabbri-Destro and Luigi Cattaneo
Traditionally, it has been assumed that the under-
standing of actions performed by others depends
on inferential reasoning.1–3 Theoretically, when
we witness the actions of others, the information
could initially be subjected to sensory processing
and then be sent to higher order ‘associationareas
where it is elaborated on by sophisticated cogni-
tive mechanisms and compared with previously
stored data. At the end of this process, we would
know what others are doing.4
It is possible that this cognitive operation
might indeed occur in some situations when
the behavior of the observed person is difficult
to interpret.5–7 However, the ease with which we
usually understand what others are doing sug-
gests that an alternative mechanism might be
involved in action perception. The essence of
this alternative system is that actions performed
by others, after being processed in the visual
system, are directly mapped onto observers’
motor representations of the same actions. The
observers are aware of the outcomes of their own
actions, so the occurrence of a neural pattern
similar to that present during their own volun-
tary motor acts will enable them to understand
the actions of others.
Evidence in favor of the existence of this direct
sensory–motor mapping mechanism came from
the discovery of a set of motor neurons, known
as mirror neurons, that fire both when a monkey
performs a given motor act and when it observes
another individual performing an identical or
similar motor act.8,9 In this article, we will first
review the basic properties of this mechanism,
which is known as the mirror mechanism. We
then examine the relevance of the mirror mecha-
nism for the interpretation of clinical syndromes
such as autism, and for the development of
motor rehabilitations strategies.
Mirror neurons were originally discovered in
the ventral premotor cortex (area F5) of the
macaque monkey.8,9 The defining characteristic
One of the most exciting events in neurosciences over the past few years
has been the discovery of a mechanism that unifies action perception and
action execution. The essence of this ‘mirror’ mechanism is as follows:
whenever individuals observe an action being done by someone else, a set
of neurons that code for that action is activated in the observers’ motor
system. Since the observers are aware of the outcome of their motor acts,
they also understand what the other individual is doing without the need
for intermediate cognitive mediation. In this Review, after discussing the
most pertinent data concerning the mirror mechanism, we examine
the clinical relevance of this mechanism. We first discuss the relationship
between mirror mechanism impairment and some core symptoms of
autism. We then outline the theoretical principles of neurorehabilitation
strategies based on the mirror mechanism. We conclude by examining
the relationship between the mirror mechanism and some features of the
environmental dependency syndromes.
KEYWORDS autism, environmental dependency syndromes, mirror neurons,
neurorehabilitation, utilization behavior
G Rizzolatti is Professor of Human Physiology and chairs the Department
of Neuroscience of the University of Parma, Parma, M Fabbri-Destro is
a Psychologist at the University of Ferrara, Ferrara, and the University
of Parma, and L Cattaneo is a Neurologist at the Center for Mind–Brain
Sciences (CIMeC) in Rovereto, Italy.
*Department of Neuroscience, University of Parma, 39 via Volturno, 43100 Parma, Italy
Received 15 October 2008 Accepted 13 November 2008
PubMed was searched using Entrez for articles published up to September 2008.
The search term was “mirror neuron” ORmirror neurons” OR “mirror neuron
system” OR “mirror system. Owing to limitations on the number of references,
we cited only articles that we judged to be most important from a theoretical or
clinical point of view.
of these neurons is that they discharge both when
the monkey performs a motor act and when the
monkey, at rest, observes another individual (a
human being or another monkey) performing
a similar motor act (Figure 1). The degree of
similarity that is required between executed
and observed motor acts in order to trigger a
given mirror neuron varies from one neuron to
another. For most mirror neurons, however, the
relationship between the effective observed and
executed motor acts is based on their common
goal (e.g. grasping), regardless of how this goal is
achieved (e.g. using a two-finger or a whole-hand
prehension). Importantly, mirror neurons do not
discharge in response to the presentation of food
or other interesting objects.
Mirror neurons have also been described in the
PFG and anterior intraparietal areas of the infe-
rior parietal lobule (IPL; Figure 1). The general
properties of parietal mirror neurons seem to be
similar to those of mirror neurons in the premotor
cortex. Like the latter neurons, the parietal
mirror neurons code for the goals of motor acts
rather than the movements from which they
are constructed.8,9
The PFG and anterior intraparietal areas are
both connected with the F5 area and the cortex
of the superior temporal sulcus. Neurons in the
superior temporial sulcus have complex visual
properties, and some respond to the observation
of motor acts done by others.10,11 However, they
lack the motor properties that are defining fea-
tures of mirror neurons, and cannot, therefore,
be considered to be part of the mirror system.
The organization of the cortical motor
To understand the functional role of mirror
neurons in the premotor cortex and IPL, it is
necessary to frame them within the modern
conceptualization of the organization of the
cortical motor system. Clear evidence exists that
most of the parietal and frontal motor areas code
for motor acts (i.e. movements with a specific
goal) rather than mere active displacement of
body parts.12–18 Even in the primary motor
cortex, approximately 40% of neurons code for
motor acts.15,18
Studies in which the properties of single neu-
rons were studied in a naturalistic context have
been particularly important for establishing this
new view on cortical motor organization.12 These
studies showed that many neurons discharge
when a motor act (e.g. grasping) is performed
with effectors as different as the right hand, the
left hand, or the mouth. Furthermore, for the
vast majority of neurons, the same type of move-
ment (e.g. an index finger flexion) that is effec-
tive at triggering a neuron during one particular
motor act (e.g. grasping) is not effective during
another motor act (e.g. scratching). By using
motor acts as classification criteria, premotor
neurons have been subdivided into various cate-
gories such as ‘grasping’, ‘reaching, ‘holding’, and
‘tearing’ neurons.
Recently, evidence was provided that both
inferior parietal and premotor (area F5) neurons
are organized in motor chains.19,20 Grasping
neurons recorded from these areas were tested in
two main conditions (Figure 2). In one condition,
a monkey reached and grasped a piece of food
located in front of it and brought it to its mouth.
In the other condition, the monkey reached
and grasped an object and placed it into a con-
tainer. The results showed that the majority of
the recorded neurons discharged with a different
intensity according to the final goal of the action
(e.g. eating or placing) in which the grasping
motor act was embedded (‘action-constrained’
neurons). This ‘chained’ organization seems to be
particularly well adapted for providing fluidity
to action execution. Individual neurons not only
code for specific motor acts, but, by virtue of
being wired to neurons that code for the subse-
quent motor acts, they facilitate the activity of
these downstream neurons, thereby ensuring
smooth execution of the intended action.
The functional role of the mirror neurons
The existence of a class of motor neurons that
discharge during the observation of actions done
by others is not as bizarre as it might initially
seem. While it is true that an action done by others
could be recognized by inference on the basis of
previous visual experience without involving the
motor system, visual perception per se does not
provide the observer with the experiential aspects
of the action. Furthermore, the mirror system
provides a particularly efficient way to establish
links between the observed action and other
actions with which it is functionally related.21
Evidence in favor of the notion that mirror
neurons mediate action understanding came
from experiments in which monkeys were not
allowed to see the actions performed by others,
but were given clues for understanding them.
In one series of experiments, monkeys were
presented with noisy motor acts (e.g. peanuts
breaking, tearing a piece of paper), which they
could either both see and hear or only hear.22
The researchers found that many mirror neurons
in area F5 responded to the sound of the motor
act, even when it was not visible.
In another series, F5 ‘grasping’ and ‘holding’
mirror neurons were tested both when the
monkey observed the experimenter grasping a
piece of food and when the monkey was pre-
vented from seeing the experimenter’s hand
movements by use of a black screen.23 Despite
the fact that the monkey could not see the hand–
object interaction (the visual triggering feature
of the recorded neurons) in the latter condition,
many mirror neurons in F5 were active in this situ-
ation. The neurons typically began to discharge at
the beginning of the hand-reaching movement,
indicating that the monkey had a representation
of the action performed behind the screen, even
when it could not see the performed motor act.
The activity of mirror neurons per se describes
only what is happening in the precise moment
of occurrence of the observed actions. There is,
however, a broader function of mirror neurons.
This function is related to the recent discovery
that most action-constrained neurons (see above)
have mirror properties and selectively discharge
when the monkey observes motor acts embedded
in a specific action (e.g. grasping for eating but
not grasping for placing; see Figure 2).19 The
activation of action-constrained mirror neurons,
therefore, codes not only ‘grasping’, but ‘grasping
for eating’ or ‘grasping for placing’. This coding
implies that when the monkey observes grasp-
ing done by another, it is able to predict, on the
basis of contextual cues (e.g. repetition, presence
of specific objects), what will be the individual’s
next motor act. In other words, the monkey is
able to understand the intentions behind the
observed motor act.
500 ms
Figure 1 A cytoarchitectonic map of the monkey cortex and an example of a mirror neuron. The upper
part of the figure shows the activity of a mirror neuron recorded from area F5. The neuron discharges both
when the monkey grasps an object (A) and when it observes the experimenter grasping the object (B).
(C) The cytoarchitectonic parcellation of the agranular frontal cortex and the parietal lobe. PE, PEc, PEip,
PF, PFG and PG are parietal areas. An enlargement of the frontal region (inset on the left) shows the
parcellation of area F5 into three parts: F5c, F5p and F5a. The mirror neurons are typically found in F5c.
The inset on the right shows the areas buried within the intraparietal sulcus. Abbreviations: AI, inferior
arcuate sulcus; AIP, anterior intraparietal area; AS, superior arcuate sulcus; C, central sulcus; FEF, frontal
eye field; IO, inferior occipital sulcus; IP, inferior precentral sulcus; L, lateral sulcus; LIP, lateral intraparietal
area; Lu, lunate sulcus; MIP, medial intraparietal area; P, principal sulcus; STS, superior temporal sulcus;
VIP, ventral intraparietal area. Permission obtained from Elsevier Ltd © Rizzolatti G and Fabbri-Destro M
(2008) Curr Opin Neurobiol 18: 179–184.
Figure 2 Action-constrained neurons in the monkey IPL. (A) Apparatus and
paradigm used for a task designed to demonstrate action-constrained neurons.
The monkey starts from the same position in all trials, reaches for an object (1)
and brings it to the mouth (2a) or places it into a container (2b). (B) Activity of three
IPL neurons during the motor task in conditions 2a (grasp to place) and 2b (grasp
to eat). Raster histograms are synchronized with the moment when the monkey
touched the object to be grasped. Unit 67 fires during grasping to eat and not
during grasping to place. Unit 161 is selective for grasping to place. Unit 158
does not show any task preference. (C) Visual responses of IPL mirror neurons
during the observation of grasping to eat and grasping to place performed by
an experimenter. Unit 87 is selective for grasping to eat, unit 39 is selective for
grasping to place and unit 80 does not display any task preference. Abbreviation:
IPL, inferior parietal lobule. Permission obtained from American Association for
the Advancement of Science © Fogassi L et al. (2005) Science 308: 662–667.
Understanding of goals and intentions
A large number of studies based on noninvasive
electrophysiological (e.g. EEG, magnetoencephalo-
graphy [MEG]) or brain imaging (e.g. PET,
functional MRI [fMRI]) techniques have demon-
strated the existence of the mirror mechanism in
humans.8,9 Brain imaging studies have enabled
the mirror areas to be located. These studies
showed that the observation of transitive actions
done by others results in an increase in blood
oxygen level-dependent (BOLD) signal not only
in visual areas, but also in the IPL and the ventral
premotor cortex, as well as the caudal part of the
inferior frontal gyrus (IFG). These latter three
areas have motor properties and closely corres-
pond to the areas that contain mirror neurons in
the monkey (Figure 3).
Both the premotor and the parietal areas of
the human mirror system show a somatotopic
organization.24 Observation of motor acts done
with the leg, hand or mouth activates the pre-
central gyrus and the pars opercularis of the IFG
in a medial-to-lateral direction, as in the classical
homunculus model of Penfield25 and Woolsey.26
In the IPL, mouth motor acts are represented ros-
trally, hand and arm motor acts are represented
caudally, and leg motor acts are represented even
more caudally and dorsally, extending into the
superior parietal lobule.
Most studies on the mirror mechanism in
humans have investigated transitive movements
such as grasping. In a recent fMRI study in which
volunteers were asked to observe video clips
showing a hand transport movement without
an effector–object interaction, activations were
found in the dorsal premotor cortex and also
in the superior parietal lobule, with the activa-
tion extending into the intraparietal sulcus.27
This finding indicates that the human brain is
endowed with a reaching mirror mechanism
that is anatomically separated from the mirror
mechanism that codes for the distal motor act.
As in the monkey, the parietal and frontal
mirror areas in humans code mostly for the
goals of motor acts. Gazzola et al.28 instructed
volunteers to observe either a human or a robot
arm grasping objects. In spite of differences in
shape and kinematics between the human and
robot arms, the parietofrontal mirror network
was activated in both conditions. Further evi-
dence in favor of goal coding was obtained in an
fMRI study based on repetition suppression29a
technique that exploits the trial-by-trial reduction
of a physiological response to repeated stimuli.
The results showed that repeated presentation of
the same goal caused suppression of the hemo-
dynamic response in the left intraparietal sulcus,
but this region was not sensitive to the trajectory
of the agent’s hand.
Unit 67
to eat
to place
Unit 161
Motor responses of mirror neurons
Unit 158
Unit 87
100 100 150
2b 2a
Unit 39
Visual responses of mirror neurons
Unit 80
to eat
to place
The study of aplasic individuals born without
arms and hands provided further evidence in
favor of a goal-coding mirror mechanism.30
During MRI scanning, two aplasic individuals
and a group of nonaplasic volunteers were
instructed to watch videos showing hand actions.
All participants also made actions with their feet,
mouths, and, in the case of the nonaplasic volun-
teers, hands. The results showed that in aplasic
individuals, the observation of hand motor acts,
which they had never themselves performed, acti-
vated the mirror areas. The communality of goals
between the never-executed hand motor acts and
those performed with the mouth and feet was the
most probable explanation for this activation.
Growing evidence exists that, in addition to goal
coding, the human mirror mechanism has a role
in the ability to understand the intentions behind
the actions of others. In an fMRI study, volunteers
observed motor acts (e.g. grasping a cup) embed-
ded in specific contexts (a condition in which the
agent’s intention could be easily understood)
or devoid of context (a condition in which the
agent’s intention was ambiguous).31 The results
showed that the mirror network was active in
both conditions. However, the understanding of
intention produced a stronger signal increase in
the caudal IFG of the right hemisphere.
The importance of the mirror system in under-
standing the intentions of others was confirmed
by a repetition-suppression fMRI experiment.32
Participants were asked to observe repeated
movies showing either the same movement or the
same action outcome regardless of the executed
movement. The result showed activity suppres-
sion in the right IPL and the right IFG when the
outcome was the same.
Movement, emotions and language
As we have discussed, the mirror mechanism
located in the parietal and frontal areas codes
mostly for the goals of observed motor acts.
However, studies that involved transcranial
magnetic stimulation (TMS) have shown that
the human motor system also responds to the
observation of movements devoid of a goal.33,34
This ‘movement mirror mechanism’ seems to
be extremely sensitive to movement kinematics.
Dayan et al.35 studied brain responses to the
observation of curved hand movements that either
obeyed or disobeyed the law—known as the 2/3-
power law—that describes the coupling between
movement curvature and velocity. Mirror hand
areas were more active during the observation of
movements that obeyed this law than during other
types of motion.
The mirror mechanism is located not only in
centers that mediate voluntary movement, but
also in cortical areas that mediate visceromotor
emotion-related behaviors.36,37 Brain imaging
studies showed that when an individual feels or
observes emotions in others caused by disgusting
stimuli or stimuli representing pain, there is
activation in two structures: the cingulate cortex
and the insula. Interestingly, the same voxels are
activated in these two structures in both ‘feeling’
and ‘observing’ conditions. This finding strongly
suggests that feeling emotions and recognizing
them in others are mediated by the same neural
It should be made clear that the anterior insula,
where the aforementioned activations were found,
has a dysgranular–agranular structure,38 and is,
therefore, cytoarchitectonically similar to motor
areas. Electrical stimulation of the insula in the
monkey produces movements of various body
37 19 18
PMv (F4)
PMv (F5c)
PMv (F5p)
46 40
Figure 3 The parietofrontal mirror system in humans. Lateral view of the human
cerebral cortex showing Brodmann cytoarchitectonic subdivision. The areas
in yellow correspond to areas that respond to the observation and execution
of hand motor acts. The left-hand panel shows an enlarged view of the frontal
lobe. The possible homology between monkey and human premotor cortex is
indicated by arrows. Note that in monkeys area F5 consists of three subareas:
F5c, F5p and F5a. Area 44 is considered to be the most likely human homolog of
area F5. Abbreviations: C, central sulcus; FEF, frontal eye field; IF, inferior frontal
sulcus; IP, inferior precentral sulcus; PMd, dorsal premotor cortex; PMv, ventral
premotor cortex; PrePMd, pre-dorsal premotor cortex; SF, superior frontal
sulcus; SP, upper part of the superior precentral sulcus. Permission obtained
from Elsevier Ltd © Rizzolatti G and Fabbri-Destro M (2008) Curr Opin Neurobiol
18: 179–184.
parts, accompanied by a variety of visceromotor
responses.39–40 Similar effects have also been
described in humans.41,42 It is, therefore, appro-
priate to define these structures as ‘mirror areas’
in which the motor response includes a visceral
In humans, the mirror mechanism is also
located in Broca’s area, which is involved in lan-
guage processing and speech production. Evidence
for a mechanism that translates heard phonemes
into the motor programs necessary to produce
them has been provided by TMS experiments.43
The mouth motor field was stimulated in volun-
teers while they heard words containing pho-
nemes requiring tongue movements (e.g. “birra”)
or not requiring tongue movements (e.g. “baffo”).
Motor evoked potentials recorded from the
tongue muscles increased with the presentation
of verbal material containing a double ‘r’ relative
to those containing a double ‘f.
The mirror system and autism
Autism spectrum disorder (ASD) is a hetero-
geneous developmental syndrome characterized
by a marked impairment in social interaction
and communication.44 Communication deficits
include disturbances in most domains of language
and are not limited to its pragmatic aspects.45
Impairment in the domains of affective links
and emotion recognition is another important
component of ASD.46 A restricted repertoire of
activity and interests, repetitive motion, and hyper-
sensitivity to certain sounds are other symptoms
that are often present in ASD.
Autism affects a variety of nervous structures,
from the cerebral cortex to the cerebellum and
brainstem.47 However, in a context of a broader
neurodevelopmental deficit, a set of ASD symp-
toms (impairment in communication, language
and emotion, as well as in the capacity to under-
stand others) seems to match the functions medi-
ated by the mirror mechanism. A hypothesis has,
therefore, been advanced that this set of deficits
might depend on an impairment of the mirror
mechanism,48,49 and there is growing evidence
to support this view.50–53
One classical EEG observation is that mu
rhythm (an EEG rhythm recorded from the motor
cortical areas) is blocked when a person makes a
voluntary movement. This rhythm is also sup-
pressed when a person observes another person
performing a movement. Oberman et al.50 used
this phenomenon to test the mirror mechanism
in children with ASD. The results showed that
although individuals with ASD exhibited a sup-
pression of mu rhythm during voluntary move-
ments, this suppression was absent when they
watched some one else performing the move-
ment (Figure 4). Martineau et al.54 have reported
similar observations.
Oberman et al.55 recently reported an inter-
esting observation concerning the mirror system
of children with ASD. The authors investigated
how familiarity between an observing indivi-
dual and a person performing a movement
modulates the entity of mu rhythm suppression.
Typically developing children and children with
ASD viewed video clips showing the hand of a
stranger performing a grasping action, the hand
of a child’s guardian or sibling performing the
same action, and the participant’s own hand per-
forming the action. The study revealed that mu
suppression depended on the familiarity of the
observer with the agent, and that children with
ASD showed mu suppression when a familiar
person performed the action but not when it was
performed by an unfamiliar person.
An fMRI study has provided strong evidence
in favor of a deficit of the mirror mechanism in
ASD. High-functioning children with ASD and
matched controls were scanned while they imi-
tated and observed emotional expressions. The
results showed a markedly weaker activation
in the IFG in children with ASD than in typi-
cally developing children. Most interestingly, the
degree of activation was inversely related to
symptom severity.53
Impaired motor facilitation during action
observation has been reported in individuals with
ASD by use of TMS.52 Furthermore, unlike typi-
cally developing individuals, children with ASD
tend not to imitate other individuals in a mirror
fashion when viewing them face-to-face.56 This
imitation peculiarity is probably attributable to
a deficit in the ability of the mirror mechanism
to superimpose another person’s movements on
one’s own.
Deficits in the mirror mechanism in ASD have
also been addressed from another perspective.57
Typically developing children and children with
ASD were tested while they observed an experi-
menter either grasping a piece of food for eating
or grasping a piece of paper to place it into a con-
tainer (Figure 5). The EMG activity of the mylo-
hyoid muscle, which is involved in opening of
the mouth, was recorded. The results showed that
observation of food grasping produced activation
of the mylohyoid muscle in typically developing
children, but not in children with ASD. In other
words, whereas the observation of an action done
by another individual intruded into the motor
system of a typically developing observer, this
intrusion was lacking in children with ASD. This
finding indicates that, in this disorder, the mirror
system is silent during action observation, and
that the immediate, experiential understanding
of the intentions of others is absent.
Both children with ASD and typically develop-
ing children were also asked to perform the two
actions described above (grasp to eat and grasp to
place) while the EMG activity of the mylohyoid
muscle was recorded.57 In typically developing
children, the muscle became active as soon they
moved the arm to reach the food. By contrast,
no mylohyoid muscle activation was observed
during food reaching and grasping in children
with ASD; activation of the muscle was evident
only when these children brought the food to
their mouths. These data indicate that children
with ASD are not only unable to organize their
own motor acts into a unitary action charac-
terized by a specific intention, but that they
also show a deficit in the mirror mechanism, as
reflected in the absence of motor activation of
the muscles involved in an observed action.
These findings show an apparent contradiction
between the cognitive capacities of children with
ASD to report the purpose of an experimenter’s
action and their lack of motor resonance with the
action. To clarify this incongruity, a further experi-
ment was performed in which typically develop-
ing children and children with ASD observed an
actor performing goal-directed motor acts and
were asked to report what the actor was doing
and why he was doing it (Rizzolatti G et al.,
unpublished data). These tasks test two different
abilities: the ability to recognize a motor act (e.g.
grasping an object) and the ability to understand
the intention behind it (e.g. grasping to eat). The
results showed that both typically developing
children and children with ASD were able to
recognize what the actor was doing, but children
with ASD failed to recognize why the act was
being performed. Children with ASD systema-
tically attributed to the actor the intention that
could be derived by the semantics of the object—
for example, an intention to cut when scissors
were shown—regardless of how the object was
grasped. This finding indicates that children
C4C3 Cz
C4C3 Cz
*** *** **
*** ** ***
B Autism spectrum disordersA Controls
Log (condition baseline)
C4C3 Cz
C4C3 Cz
** ***
Figure 4 Absence of mirror EEG responses in autism. The charts show suppression of the mu rhythm
in controls (A) and patients with autism spectrum disorder (B) during observation of movement of an
inanimate object (ball, pale green) or movements made with a hand (hand, green), and during active
hand movements made by the individual from whom recordings were being taken (move, red). The bars
represent the amount of mu activity in central scalp locations; C3, Cz and C4 refer to scalp coordinates
of the 10/20 EEG system. Significant suppression of this activity, indicated by asterisks, is present for
the hand observation condition only in controls, showing that patients with autism spectrum disorder
fail to respond in a standard way to the observation of other people’s actions. Permission obtained from
Elsevier Ltd © Oberman LM et al. (2005) Brain Res Cogn Brain Res 24: 190–198.
with ASD interpret the behavior of others on the
basis of the standard use of objects rather than
the actual behavior of a person performing a
task. Children with ASD, therefore, seem to lack
the ability to read the intentions of others on the
basis of behavior.
Figure 5 Motor behavior in typically developing children and children with ASD. This experiment was
designed to assess whether an action-constrained motor organization is present in typically developing
children and children with ASD.57 (A) Schematic representation of the tasks. The individual reaches for an
item on a plate and either brings it to their mouth or puts it into a container placed on their shoulder. Time
course for typically developing children (B) and children with ASD (C) of the rectified electromyographic
activity of mouth-opening muscles during the execution (left side) and observation (right side) of the
‘bringing-to-the-mouth’ action (red line) and of the ‘placing’ action (blue line). All curves are aligned with
the moment of object lifting from the touch-sensitive plate (time = 0). The results demonstrate a lack of
anticipatory motor activity during execution and a lack of mirror motor activation during observation of a
given action in children with ASD. Abbreviations: ASD, autism spectrum disorder; EMG, electromyography.
The mirror mechanism and motor
As well as having a role in action understanding,
the mirror mechanism also modulates the motor
behavior of the observer. This function forms
the basis for the imitation of simple motor acts58
and for learning through imitation.59 Particularly
interesting from a clinical point of view was the
demonstration that the mirror mechanism is
involved in the building of motor memories. The
most convincing evidence for such a role came
from studies by Stefan et al.60,61 that involved
TMS. The authors showed that when partici-
pants simultaneously performed and observed
congruent movements, the learning of these
movements was potentiated with respect to
learning through motor training alone. These
findings indicate that the coupling of observation
and execution strongly facilitates the formation
of motor memories.
Could this mechanism be exploited for motor
rehabilitation? Many current behavioral neuro-
rehabilitation techniques use strategies that
induce long-term plasticity in the motor cortex
either by depressing activity on the unaffected side
or by potentiating activity on the affected
side.62 The possibility that plasticity might be
induced in the motor cortex by coupling action
observation and execution represents the theo-
retical basis of a recent study that examined
the effect of an 18-day cycle of active motor
training with the paretic limb in two groups
of patients with chronic stabilized stroke in
the middle cerebral artery territory.63 The test
group was required to perform hand motor acts
prompted by movies showing similar motor
acts, whereas the control group performed the
same motor training without any visual cues.
Functional assessment of the upper limb showed
a significant improvement in the test group
relative to the control group.
The mirror mechanism probably also forms
the neurophysiological basis for ‘mirror therapy’
(the word ‘mirror’ being used here in its literal
sense), which has been shown to improve upper-
limb function in patients with stroke.64,65
In mirror-therapy protocols, the patients are
required to perform movements with their
nonparetic hand while watching the hand and
its reflection in a parasagittal mirror. This proce-
dure gives a visual illusion of movement of the
paretic hand. The generation of cortical plas-
ticity and the consequent rehabilitative results
strongly suggest a role in patient improvement
for a mechanism that matches seen and executed
actions, thereby implicating the mirror mecha-
nism in this process.66
Deficits in the control of mirror mechanisms
Clinical observations have shown that frontal
lesions can cause a series of disturbances charac-
terized by the appearance of forced motor behavior
triggered by external stimuli.67 Among these
manifestations, imitation behavior is particularly
interesting in relation to the mirror mechanism.
The main feature of this syndrome is the sponta-
neous imitation of motor acts done by others, and
it is considered to be part of the so-called ‘environ-
mental dependency syndrome’.68 The condi-
tion arises from unilateral, or, more frequently,
prefrontal lesions.68,69 Imitation
behavior is generally attributed to an imbalance
between exogenously and endogenously deter-
mined behaviors. The observation of actions done
by others leads to the coding of potential motor
acts in the parietal and premotor mirror areas by
means of the mirror mechanism. These poten-
tial motor acts typically do not determine overt
movements in the healthy adult brain because the
manifestation of these acts is suppressed by the
frontal lobe. Damage to this lobe would destroy
this control mechanism, thereby transforming the
potential motor acts into actual motor behavior.
In view of the temporal latency between observa-
tion and imitation that patients often show, an
additional mechanism could be also involved, but
the essence of the phenomenon seems to depend
on a release of potential motor acts.
Echopraxia is a term that describes forced and
uncritical imitation of behaviors. The exogenously
triggered behavior is sustained through endo-
genous mechanisms, resulting in its perseveration.
In view of the simplicity of the imitated behaviors,
combined with the total lack of criticism of the
patient to the imitated behavior, echopraxia is
perceived as a distinct disorder from imitation
behavior. Echopraxia can arise in the context of
basal ganglia dysfunction, as well as after frontal
lobe damage. It is probable, however, that in both
cases the mechanism that underlies echopraxia is
a disinhibition of the mirror areas through loss
of suppression by the frontal lobe.70
The discovery of the mirror mechanism radi-
cally changed our views on how individuals
understand actions, intentions and emotions.
The identification of this mechanism has had
a profound impact on a variety of disciplines,
ranging from cognitive neurosciences to soci-
ology and philosophy. Until recently, this
discovery had influenced clinical research to a
much lesser degree. However, it has now provided
deeper insights into the interpretation of certain
neurological syndromes, such as the environ-
mental dependency syndrome, and has provided
a new theoretical basis for establishing rehabili-
tation techniques in patients with motor deficits
following stroke.
Autism is one condition in which the discov-
ery of the mirror neuron mechanism could have
important practical implications in the future.
Recent experimental data suggest that indivi-
duals with ASD have a deficit in representing
goal-directed actions, both when the actions are
performed and when they are observed. Children
with ASD, therefore, show impairments in
organizing their own motor acts according to an
action goal, as well as in using this motor mecha-
nism to understand the intentions of others.
This new view on ASD could be used to establish
new rehabilitation strategies based on a motor
approach. The rationale of such an approach is
that if the motor knowledge of individuals with
ASD is improved, their social knowledge and
behavior would also be enhanced.
The mirror mechanism is a neural system that
unifies action perception and action execution
The mirror mechanism is organized into two
main cortical networks, the first being formed
by the parietal lobe and premotor cortices,
and the second by the insula and anterior
cingulate cortex
The role of the mirror mechanism is to provide
a direct understanding of the actions and
emotions of others without higher order
cognitive mediation
Limited development of the mirror mechanism
seems to determine some of the core aspects
of autism spectrum disorders
The recently demonstrated link between limited
development of the mirror mechanism and that
of some aspects of the motor system suggests
that rehabilitation in children with austism
spectrum disorder should take into account
both motor and cognitive strategies
The use of action-observation-based protocols
could represent a new rehabilitation strategy to
treat motor deficits after stroke
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This study was supported
by European Union Contract
012738, Neurocom, by
PRIN 2006 to GR and by
Fondazione Monte Parma.
MF-D was supported by
Fondazione Cassa
di Risparmio di Ferrara.
Competing interests
The authors declared no
competing interests.
... While different studies have implicated a number of cortical regions in the MNS in humans, core regions include the posterior inferior frontal gyrus, including ventral premotor cortex (POP) and rostral inferior parietal lobule (SMG), which are thought to be homologous to the regions originally identified in monkeys (see Iacoboni and Dapretto 2006;Kilroy Communicated by Melvyn A. Goodale. et al. 2019;Molenberghs et al. 2012;Rizzolatti et al. 2009). The action observation network (AON) is a broader network that includes regions that are active when watching actions, but that may not also be active when the individual performs that same action and thus the MNS is a specific subdivision of the AON (see Kilroy et al. 2019). ...
... Autism spectrum disorder (ASD) is a neurodevelopmental disorder involving deficits in social interactions and communication and the presence of repetitive behaviors or specialized interests (American Psychiatric Association 2013). Given the putative role of the AON in imitation, theory of mind, empathy, and language, behaviors which are impaired in ASD, a number of studies have proposed MNS or AON dysfunction in ASD Ramachandran and Oberman 2006;Rizzolatti and Fabbri-Destro 2010;Rizzolatti et al. 2009;Williams 2008), with some studies demonstrating atypical functioning of the MNS or AON in ASD (for reviews, Hamilton 2013; Perkins et al. 2010). Neuroimaging, such as PET and fMRI, as well as EEG studies, using mu suppression, have been used to examine the MNS or AON in ASD. ...
Full-text available
The mirror neuron system consists of fronto-parietal regions and responds to both goal-directed action execution and observation. The broader action observation network is specifically involved in observation of actions and is thought to play a role in understanding the goals of the motor act, the intention of others, empathy, and language. Many, but not all, studies have found mirror neuron system or action observation network dysfunction in autism spectrum disorder. The objective of this study was to use observation of a goal-directed action fMRI paradigm to examine the action observation network in autism spectrum disorder and to determine whether fronto-parietal activation is associated with language ability. Adolescents with autism spectrum disorder (n = 23) were compared to typically developing adolescents (n = 20), 11–17 years. Overall, there were no group differences in activation, however, the autism spectrum group with impaired expressive language (n = 13) had significantly reduced inferior frontal and inferior parietal activation during action viewing. In controls, right supramarginal gyrus activation was associated with higher expressive language; bilateral supramarginal and left pars opercularis activation was associated with better verbal-gesture integration. Results suggest that action-observation network dysfunction may characterize a subgroup of individuals with autism spectrum disorder with expressive language deficits. Therefore, interventions that target this dysfunctional network may improve expressive language in this autism spectrum subgroup. Future treatment studies should individualize therapeutic approaches based on brain-behavior relationships.
... The list of the top-20 most cited articles is depicted in Table 2 [3,4,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. The most cited document was "Brain-computer interfaces, a review" by Nicolas-Alfonso et al., (997 citations), followed by "Brain-computer interfaces in neurological rehabilitation" by J. Daly and J.R. Wolpaw (708 citations) [3,4]. ...
... The ultimate goal is to use EEG-based BCI and help patients with paralysis disabilities to communicate and control their environment, including external robotic devices and prosthetics, as in patients with ALS/LiS [3,4,17,18,26]. In addition, the recovery of neural function and motor function restoration in patients after stroke or SCI could be facilitated on the basis of rehabilitative BCIs in conjunction with virtual reality-assisted training and behavioral physiotherapy by inducing neural plasticity [3,4,18,20,23,26,28]. Indeed, the addition of BCI training to behaviorally oriented physiotherapy could induce functional improvements in motor function in patients with chronic stroke symptoms, without residual finger movements, and may open a new door in stroke neurorehabilitation [15]. ...
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Background: There is increasing interest in the role of EEG in neurorehabilitation. We primarily aimed to identify the knowledge base through highly influential studies. Our secondary aims were to imprint the relevant thematic hotspots, research trends, and social networks within the scientific community. Methods: We performed an electronic search in Scopus, looking for studies reporting on rehabilitation in patients with neurological disabilities. We used the most influential papers to outline the knowledge base and carried out a word co-occurrence analysis to identify the research hotspots. We also used depicted collaboration networks between universities, authors, and countries after analyzing the cocitations. The results were presented in summary tables, plots, and maps. Finally, a content review based on the top-20 most cited articles completed our study. Results: Our current bibliometric study was based on 874 records from 420 sources. There was vivid research interest in EEG use for neurorehabilitation, with an annual growth rate as high as 14.3%. The most influential paper was the study titled "Brain-computer interfaces, a review" by L.F. Nicolas-Alfonso and J. Gomez-Gill, with 997 citations, followed by "Brain-computer interfaces in neurological rehabilitation" by J. Daly and J.R. Wolpaw (708 citations). The US, Italy, and Germany were among the most productive countries. The research hotspots shifted with time from the use of functional magnetic imaging to EEG-based brain-machine interface, motor imagery, and deep learning. Conclusions: EEG constitutes the most significant input in brain-computer interfaces (BCIs) and can be successfully used in the neurorehabilitation of patients with stroke symptoms, amyotrophic lateral sclerosis, and traumatic brain and spinal injuries. EEG-based BCI facilitates the training, communication, and control of wheelchair and exoskeletons. However, research is limited to specific scientific groups from developed countries. Evidence is expected to change with the broader availability of BCI and improvement in EEG-filtering algorithms.
... This study suggests that the use of VR in combination with cycloergometer exercises provides an improvement in gait and dynamic balance Tinetti subdimensions. Furthermore, after analyzing the encephalograms, it can be seen that this type of treatment acts on different brain areas, probably at a mirror neuron system [53] involved in task planning, with results showing improvement at the motor level. Regarding spasticity, unlike in our study, other studies [37,54] show evidence of the decrease in spasticity with the use of VR and video games in stroke patients. ...
Full-text available
A stroke is a neurological condition with a high impact in terms of physical disability in the adult population, requiring specific and effective rehabilitative approaches. Virtual reality (VR), a technological approach in constant evolution, has great applicability in many fields of rehabilitation, including strokes. The aim of this study was to analyze the effects of a traditional neurological physiotherapy-based approach combined with the implementation of a specific VR-based program in the treatment of patients following rehabilitation after a stroke. Participants (n = 24) diagnosed with a stroke in the last six months were randomly allocated into a control group (n = 12) and an experimental group (n = 12). Both groups received one-hour sessions of neurological physiotherapy over 6 weeks, whilst the experimental group was, in addition, supplemented with VR. Patients were assessed through the Daniels and Worthingham Scale, Modified Ashworth Scale, Motor Index, Trunk Control Test, Tinetti Balance Scale, Berg Balance Scale and the Functional Ambulation Classification of the Hospital of Sagunto. Statistically significant improvements were obtained in the experimental group with respect to the control group on the Motricity Index (p = 0.005), Trunk Control Test (p = 0.008), Tinetti Balance Scale (p = 0.004), Berg Balance Scale (p = 0.007) and the Functional Ambulation Classification of the Hospital of Sagunto (p = 0.038). The use of VR in addition to the traditional physiotherapy approach is a useful strategy in the treatment of strokes.
... Diferentes estudios comprueban que las neuronas en espejo se activan y forman circuitos cerebrales cuando un sujeto realiza una acción, pero también cuando otro sujeto la observa; de manera que estas neuronas son capaces de transformar la información sensorial específica en un formato motor, sin necesidad de una mediación cognitiva intermedia, formando todo ello parte de un sistema de percepción-emociónejecución, por medio de un mecanismo que relaciona directamente la representación sensorial de las acciones observadas con la propia representación motora de esas mismas acciones (mecanismo de espejo o resonancia); aunque el aprendizaje de habilidades motoras no solo depende de la observación, sino también de la imitación, que da lugar a una mayor activación de las neuronas espejo 10 . ...
... Emotional contagion is rooted in the MNS, which transforms sensory representations of others' behavior into one's own visceromotor representations and allows understanding others' actions according to the perception-action model [59]. In more detail, it has been suggested that the inferior frontal gyrus identifies the goals or intentions of actions by their resemblance to stored representations for these actions [60]. Despite the unquestioned involvement in cognitive empathy, several studies have also described a putative role of the insula in the mirror mechanism of emotions: in fact, it has been demonstrated that there is a clear overlap between insular activation elicited by one's own and others' emotions, such as disgust [59,61,62]. ...
Full-text available
The aims of the study were to assess empathy deficit and neuronal correlates in logopenic primary progressive aphasia (lv-PPA) and compare these data with those deriving from amnesic Alzheimer’s disease (AD). Eighteen lv-PPA and thirty-eight amnesic AD patients were included. Empathy in both cognitive and affective domains was assessed by Informer-rated Interpersonal Reactivity Index (perspective taking, PT, and fantasy, FT, for cognitive empathy; empathic concern, EC, and personal distress, PD, for affective empathy) before (T0) and after (T1) cognitive symptoms’ onset. Emotion recognition was explored through the Ekman 60 Faces Test. Cerebral FDG-PET was used to explore neural correlates underlying empathy deficits. From T0 to T1, PT scores decreased, and PD scores increased in both lv-PPA (PT z = −3.43, p = 0.001; PD z = −3.62, p < 0.001) and in amnesic AD (PT z = −4.57, p < 0.001; PD z = −5.20, p < 0.001). Delta PT (T0–T1) negatively correlated with metabolic disfunction of the right superior temporal gyrus, fusiform gyrus, and middle frontal gyrus (MFG) in amnesic AD and of the left inferior parietal lobule (IPL), insula, MFG, and bilateral superior frontal gyrus (SFG) in lv-PPA (p < 0.005). Delta PD (T0-T1) positively correlated with metabolic disfunction of the right inferior frontal gyrus in amnesic AD (p < 0.001) and of the left IPL, insula, and bilateral SFG in lv-PPA (p < 0.005). Lv-PPA and amnesic AD share the same empathic changes, with a damage of cognitive empathy and a heightening of personal distress over time. The differences in metabolic disfunctions correlated with empathy deficits might be due to a different vulnerability of specific brain regions in the two AD clinical presentations.
... Nojima et al. [14] confirmed by transcranial magnetic stimulation that the improvement of motor function after MT training was more associated with the remodeling of the major motor cortical areas. In MT training, constant visual and somatosensory stimulation could activate the MNS, induce neural remodeling [18,19], and cause upper motor function recovery. In addition, in MT, patients performed bilateral upper limb motor training independently or with assistance, and motor cortical areas were extensively activated when bilateral limbs performed symmetrical movements [20,21], and it can be assumed that mirror visual feedback could ease some of the motor pathways on the affected side and promote the recovery of limb motor function. ...
Full-text available
Background: Rehabilitation of upper extremity hemiplegia after stroke remains a great clinical challenge, with only 20% of patients achieving a basic return to normal hand function. How to promote the recovery of motor function at an early stage is crucial to the life of the patient. Objectives: To invest the effects of additional mirror therapy in improving upper limb motor function and activities of daily living in acute and subacute stroke patients, and further explore the effects of other factors on the efficacy of MT. Methods: Participants who presented with unilateral upper extremity paralysis due to a first ischemic or hemorrhagic stroke were included in the study. They were randomly allocated to the experimental or control group. Patients in the control group received occupational therapy for 30 minutes each session, six times a week, for three weeks, while patients in the experimental group received 30 minutes of additional mirror therapy based on occupational therapy. The primary outcome measures were Fugl-Meyer Assessment-upper extremity (FMA-UE), Action Research Arm Test (ARAT), and Instrumental Activity of Daily Living (IADL) which were evaluated by two independent occupational therapists before treatment and after 3-week treatment. A paired t-test was used to compare the values between pretreatment and posttreatment within an individual group. Two-sample t-test was utilized to compare the changes (baseline to postintervention) between the two groups. Results: A total of 52 stroke patients with unilateral upper extremity motor dysfunction who were able to actively cooperate with the training were included in this study. At baseline, no significant differences were found between groups regarding demographic and clinical characteristics (P > 0.05 for all). Upper limb motor function and ability to perform activities of daily living of the patients were statistically improved in both groups towards the third week (P < 0.05). In addition, statistical analyses showed more significant improvements in the score changes of FMA-UE and IADL in the experimental group compared to the control group after treatment (P < 0.05), but no significant difference was observed in the ARAT score changes between the two groups (P > 0.05). The subgroup analysis showed that no significant heterogeneity was observed in age, stroke type, lesion side, and clinical stage (P > 0.05). Conclusion: In conclusion, some positive changes in aspects of upper limb motor function and the ability to perform instrumental activities of daily living compared with routine occupational therapy were observed in additional mirror therapy. Therefore, the application of additional mirror therapy training should be reconsidered to improve upper extremity motor in stroke patients.
... The lateral part of this structure (lateral parietal area, LIP) houses "gaze mirror neurons, " i.e., neurons that fire both, when looking at a specific location and when watching someone else gazing toward the same location (Shepherd et al., 2009). Such neurons might cause attentional shifts through matching the observed gaze direction with one's own visual attention, similar to the functioning of mirror neurons of the motor system (Rizzolatti et al., 2009). Visuo-social areas of the fusiform gyrus and STS are moreover interconnected with an extended face processing network that might further modulate gaze following responses (Ishai et al., 2005;Vuilleumier and Pourtois, 2007). ...
Full-text available
Social gaze has received much attention in social cognition research in both human and non-human animals. Gaze following appears to be a central skill for acquiring social information, such as the location of food and predators, but can also draw attention to important social interactions, which in turn promotes the evolution of more complex socio-cognitive processes such as theory of mind and social learning. In the past decades, a large number of studies has been conducted in this field introducing differing methodologies. Thereby, various factors influencing the results of gaze following experiments have been identified. This review provides an overview of the advances in the study of gaze following, but also highlights some limitations within the research area. The majority of gaze following studies on animals have focused on primates and canids, which limits evolutionary interpretations to only a few and closely related evolutionary lineages. This review incorporates new insights gained from previously understudied taxa, such as fishes, reptiles, and birds, but it will also provide a brief outline of mammal studies. We propose that the foundations of gaze following emerged early in evolutionary history. Basic, reflexive co-orienting responses might have already evolved in fishes, which would explain the ubiquity of gaze following seen in the amniotes. More complex skills, such as geometrical gaze following and the ability to form social predictions based on gaze, seem to have evolved separately at least two times and appear to be correlated with growing complexity in brain anatomy such as increased numbers of brain neurons. However, more studies on different taxa in key phylogenetic positions are needed to better understand the evolutionary history of this fundamental socio-cognitive skill.
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Hi, Andy—Here at last is my endorsement of your terrific book. Use as much or as little as you wish and edit as needed. (You don’t need to run it by me.) You’ve written a book for the ages. May it reach millions. God bless you! Tom __________________ In Parenting for Faith, Andy Mullins tells of a young couple going through a very difficult time. They had four young children, he was changing jobs, she had just been diagnosed with cancer, they were arguing incessantly and going to counseling. Then the father “realized that I had to stop leaving the spiritual leadership in our home to my wife. I started to bring the kids together for our family prayers every night. I now ask my daughter to light a candle at the picture of Our Lady in the hallway. Each of us leads a prayer.” The father’s stepping up to the plate “changed everything” for this struggling family. This is just one of dozens of this book’s inspiring stories of hope, faith, love, and fortitude in the face of whatever sufferings life may bring. Andy Mullins is a master storyteller and a master teacher who draws beautifully on his long and rich experience as head of a school for boys. Every chapter shows us how we can—through the power of prayer, the sacraments, good example, and direct teaching—undertake our biggest challenge: making God real for our children and bringing them into a loving, faith-filled relationship with God and others. This marvelous book is the best thing I’ve read on my Catholic faith in a long time, and the best I’ve ever read on the sacraments. Very often we learn about our faith on such a thin level that it doesn’t begin to shape our life. There is so much more to know and appreciate. This book opens our eyes to the treasures at our disposal. As a grandparent of 15, I plan at some point to give a copy of this book to each of them—both for their own spiritual journey and for the children they may someday raise.—Thomas Lickona, professor of education and author of How to Raise Kind Kids Thomas Lickona, Ph.D. Director, Center for the 4th and 5th Rs (Respect and Responsibility)
Objective: To investigate the feasibility of a combined high-frequency rTMS (HF-rTMS) with action observation and execution (AOE) on social interaction and communication in children with Autistic Spectrum Disorder (ASD). Materials and methods: Fifteen children underwent 10 sessions of 5-Hz HF-rTMS on the right inferior frontal gyrus combined with AOE. An experimental group received the real HF-rTMS while the control group received the sham one. For the AOE protocol, they were instructed to watch and imitate a video showing the procedure, including reaching and grasping tasks, gustatory tasks, and facial expressions. Their behavioural outcomes were evaluated using the Vineland Adaptive Behaviour Scale (VABS) and electroencephalograms (EEGs) recorded at three time points: baseline, immediately after each treatment, and at the 1-week follow-up after the 10th treatment. Results: There was a reduction in the VABS subitem scores of the experimental group, including the receptive, expressive, domestic, and community scores but no such reductions were observed in the control group. For the EEG, the beta rhythm at C3 and C4 increased in the experimental group. Additionally, positive correlations were observed between changes in the scores for the expressive subitem and changes in the beta rhythm on the C4 electrode at baseline and immediately after treatment in the experimental group. The control group showed no significant differences in any items for both observation and imitation times. Conclusion: Ten sessions of HF-rTMS combined with AOE could improve both the subitems of communication and daily living skills domain in children aged 7-12 years with ASD. Although it is still inconclusive, this behavioural improvement may be partly attributable to increased cortical activity, as evidenced by beta rhythms.
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Various deficits in the cognitive functioning of people with autism have been documented in recent years but these provide only partial explanations for the condition. We focus instead on an imitative disturbance involving difficulties both in copying actions and in inhibiting more stereotyped mimicking, such as echolalia. A candidate for the neural basis of this disturbance may be found in a recently discovered class of neurons in frontal cortex, 'mirror neurons' (MNs). These neurons show activity in relation both to specific actions performed by self and matching actions performed by others, providing a potential bridge between minds. MN systems exist in primates without imitative and ‘theory of mind’ abilities and we suggest that in order for them to have become utilized to perform social cognitive functions, sophisticated cortical neuronal systems have evolved in which MNs function as key elements. Early developmental failures of MN systems are likely to result in a consequent cascade of developmental impairments characterised by the clinical syndrome of autism.
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When a child reaches toward a cookie, the watching parent knows immediately what the child wants. The neural basis of this ability to interpret other people's actions in terms of their goals has been the subject of much speculation. Research with infants has shown that 6 month olds respond when they see an adult reach to a novel goal but habituate when an adult reaches to the same goal repeatedly. We used a similar approach in an event-related functional magnetic resonance imaging experiment. Adult participants observed a series of movies depicting goal-directed actions, with the sequence controlled so that some goals were novel and others repeated relative to the previous movie. Repeated presentation of the same goal caused a suppression of the blood oxygen level-dependent response in two regions of the left intraparietal sulcus. These regions were not sensitive to the trajectory taken by the actor's hand. This result demonstrates that the anterior intraparietal sulcus represents the goal of an observed action.
This book is based on the Lane Medical Lectures which Penfield gave in 1947. Four hundred craniotomies performed between 1928 and 1947 presented the opportunity to stimulate various parts of the cerebral cortex with electrical currents and to record the objective (movements) and subjective effects. The results of these studies are presented clearly and with the necessary details. Objective results and interpretation are sharply separated. The investigations give a very complete description of the organization of the sensorimotor cortex. The primitive character of the movements is emphasized. They are "not more complicated than those the newborn infant is able to perform." Evidence of the existence of a secondary motor cortex is also presented. A certain muscle may show widely separated cortical foci when it is used in different functional groupings. Central overlap exists clearly in precentral and postcentral gyrus. The authors assume that the diencephalon plays an important role in
In humans and monkeys the mirror neuron system transforms seen actions into our inner representation of these actions. Here we asked if this system responds also if we see an industrial robot perform similar actions. We localised the motor areas involved in the execution of hand actions, presented the same subjects blocks of movies of humans or robots perform a variety of actions. The mirror system was activated strongly by the sight of both human and robotic actions, with no significant differences between these two agents. Finally we observed that seeing a robot perform a single action repeatedly within a block failed to activate the mirror system. This latter finding suggests that previous studies may have failed to find mirror activations to robotic actions because of the repetitiveness of the presented actions. Our findings suggest that the mirror neuron system could contribute to the understanding of a wider range of actions than previously assumed, and that the goal of an action might be more important for mirror activations than the way in which the action is performed.
How does imitation occur? How can the motor plans necessary for imitating an action derive from the observation of that action? Imitation may be based on a mechanism directly matching the observed action onto an internal motor representation of that action (“direct matching hypothesis”). To test this hypothesis, normal human participants were asked to observe and imitate a finger movement and to perform the same movement after spatial or symbolic cues. Brain activity was measured with functional magnetic resonance imaging. If the direct matching hypothesis is correct, there should be areas that become active during finger movement, regardless of how it is evoked, and their activation should increase when the same movement is elicited by the observation of an identical movement made by another individual. Two areas with these properties were found in the left inferior frontal cortex (opercular region) and the rostral-most region of the right superior parietal lobule.
Humans permanently monitor others' behaviour and reason about their goals and intentions. Recent studies provided evidence suggesting that a very simple mechanism might underlie these functions. When observing stereotypic actions of others, goal inference seems to work through internal simulation of these actions in the self. However, less is known about the functional mechanisms and brain areas that are involved in inferring goals from others' actions when these actions are not stereotypic. Here we investigated the neural processes that are involved in goal inference processing of simple, non-stereotypic actions using functional brain imaging. We developed a paradigm in which we compared four simple finger lifting movements that differed in plausibility and intentionality as varied by action context. We found three regions that seem to be involved in goal inference processing of non-stereotypic implausible actions: (1) The superior temporal sulcus, (2) the right inferior parietal cortex, at the junction with the posterior temporal cortex (TPJ), and (3) the angular gyrus of the inferior parietal lobule. In line with teleological reasoning accounts of action understanding, inferring others' goals from non-stereotypic actions seems to be the outcome of context-sensitive inferential processing. In agreement with previous findings, we found the mirror system to be more strongly activated for intentionally produced actions [Iacoboni, M., Molnar-Szakacs, I., Gallese, V., Buccino, G., Mazziotta, J.C., Rizzolatti, G., 2005. Grasping the intentions of others with one's own mirror neuron system. PLoS Biol. 3, e79.], indicating an involvement of the IFG in representing intentional actions. Our findings support the idea that goal inference processing for non-stereotypic actions is primarily mediated by reasoning about action and context rather than by a direct mapping process via the mirror system.
This paper reports and illustrates in figurine style results obtained by electrical stimulation of the cortex in 20 patients and by recording of cortical evoked potentials (EPs) in 13 of these patients, whose surgery required wide exposure of the Rolandic or paracentral regions of the cortex. This study is unique in that cutaneous receptive fields related to specific cortical sites were defined by mechanical stimulation, as is done in animals, in contrast to electrical stimulation of peripheral nerves at fixed sites, as in scalp EP recordings. Observations were made on pre- and postcentral gyri, on the second somatic sensory-motor area, on the supplementary motor area, and on the supplementary sensory area. In two patients with phantom limb pain, the pain was elicited in one on stimulation of the postcentral arm area, and in the other on stimulation of the supplementary sensory leg area. Surgical removal of these areas had the immediate effect of abolishing the phantoms and the pain. Long-term follow-up review was not possible. In one patient with severe Parkinson's disease, stimulating currents subthreshold for the elicitation of movement resulted in disappearance of tremor and rigidity for short periods after stimulation of the precentral gyrus. The possible patterns of organization of the human pre- and postcentral areas are considered and compared with those of the chimpanzee and other primates. In patients in whom data from pre- and postcentral gyri were adequate, it appeared that the precentral face-arm boundary is situated 1 to 2 cm higher than the corresponding postcentral boundary.