Self-awareness and action
Sarah-Jayne Blakemore?and Chris Frithy
In this review we discuss how we are aware that actions are
self-generated. We review behavioural data that suggest that a
prediction of the sensory consequences of movement might be
used to label actions and their consequences as self-generated.
We also describe recent functional neuroimaging experiments
and studies of neurological and psychiatric patients, which
suggest that the parietal cortex plays a crucial role in the
awareness of action.
?Institute of Cognitive Neuroscience, University College London,
17 Queen Square, London WC1N 3AR, UK
yCorrespondence: Wellcome Department of Imaging Neuroscience,
Institute of Neurology, University College London, 12 Queen Square,
London WC1N 3BG, UK
Current Opinion in Neurobiology 2003, 13:219–224
This review comes from a themed issue on
Edited by Brian Wandell and Anthony Movshon
0959-4388/03/$ – see front matter
? 2003 Elsevier Science Ltd. All rights reserved.
functional magnetic resonance imaging
position emission tomography
‘She raised one hand and flexed its fingers and won-
dered, as she had sometimes before, how this thing,
this machine for gripping, this fleshy spider on the end
of her arm, came to be hers, entirely at her command.
Or did it have some little life of its own? She bent her
finger and straightened it. The mystery was in the
instance before it moved, the dividing moment
between not moving and moving, when her intention
took effect. It was like a wave breaking. If she could
only find herself at the crest, she thought, she might
find the secret of herself, that part of her that was
really in charge. She brought her forefinger closer to
her face and stared at it, urging it to move. It remained
still because she was pretending, she was not entirely
serious, and because willing it to move, or being about
to move it, was not the same as actually moving it. And
when she did crook it finally, the action seemed to
start in the finger itself, not in some part of her mind.
When did it know to move, when did she know to
Ian McEwan, Atonement
In this review, we discuss studies on action and awareness
in the context of a well-established framework of motor
control. This framework proposes that our actions and
interactions with objects are represented in the form of
internal models . The crucial component of the for-
ward model, a type of internal model, is the predicted
sensory consequence(s) of movement, which can be
compared with the actual sensory consequence(s) of
movement and used to optimise motor control [1,2,
Davidson and Wolpert, this issue]. Here, we suggest that
of our awareness of action.
What aspects of action are we aware of?
Being aware of initiating and controlling actions is a major
component of conscious experience, but many aspects of
action occur without our awareness. Evidence that sensa-
tions associated with actual movements are unavailable to
awareness comes from a study in which the sensory
consequences of movement were made to deviate from
a subject’s expectations . In this study, the subject’s
task was to draw a straight line on a computer screen.
Subjects could not see their arm or hand and were given
false feedback on the screen about the trajectory of their
arm movement. Thus, they had to make considerable
However, verbal reports indicated that subjects were
unaware that they were making deviant movements –
they claimed to have made straight movements. These
results suggest that we are aware of the movements we
is some evidence to suggest that the exact threshold
above which the discrepancy between the intended
and actual movement becomes available to awareness
depends to some extent on the task at hand [4?,5]. When
and the sensory (visual) consequences, subjects seem to
become aware that the movement is not their own when
or by 150 ms temporally [4?]. If subjects are not asked to
discrepancy, even when the sensory (tactile) conse-
quences of their movements are delayed by 300 ms .
In his studies of motor consciousness, Libet investigated
the time at which awareness emerges during the genera-
tion of an action. Libet  asked healthy volunteers to
estimate retrospectively the time at which they initiated a
finger movement (the time at which their finger started to
move; the ‘M’ judgement). The volunteers consistently
anticipated the actual starting time of the movement by
50–80 ms. Recently, Haggard and Magno  carried out a
Current Opinion in Neurobiology 2003, 13:219–224
series of experiments that were based on the Libet
paradigm. They showed that the perceived time of move-
ment onset is slightly delayed (by about 75 ms) if the
motor cortex is stimulated using transcranial magnetic
stimulation (TMS), whereas this stimulation causes a far
greater delay (of around 200 ms) in the initiation of the
actual movement . These observations support the
idea that our awareness of initiating a movement is not
because such signals are not available until after the limb
has started moving. Instead our awareness appears to be
linked, at least in part, to a signal that precedes the
movement. One signal that is available before a move-
ment is initiated is the prediction of the sensory con-
sequences of the movement. Perhaps one signal that we
are aware of when making a movement is this prediction,
rather than the movement itself. Sensory feedback from
the movement would also be important to check the
movement was completed as planned.
Action in the imagination
Sensory prediction might underlie the ability to prepare
and imagine movements. It is well established that ima-
gining a movement and preparing to move activate a
a movement [8–10,11?,12??]. Healthy subjects can con-
fuse actions performed in the imagination and in reality
when they are asked to recall such actions twoweeks later
[13?]. A recent functional magnetic resonance imaging
(fMRI) study scanned subjects while they executed
movements or imagined making the same movements.
A direct comparison between brain activity during ima-
gined and executed movements revealed that imagining
movements activates the left posterior and inferior par-
ietal lobe to a greater extent than executing the same
movement . Subjects show a speed-accuracy trade off
for imaginary as well as real movements, but this effect is
lost in the imaginary movements of patients with parietal
lesions [15,16?]. Taken together, these data suggest that
the parietal lobe plays an important role in the generation
are necessary for motor imagery. The same lack of speed-
accuracy trade off is seen in imagined movements made
by schizophrenic patients with delusions of control [17?].
This is in line with the proposal that delusions of control
are associated with a faulty internal representation of
Awareness of intentions
Are we aware of our intentions to move? In a second task,
Libet asked volunteers to indicate the time at which they
became aware of having the ‘urge’ to make a movement
(that is, of their will or intention to move; the ‘W’
judgement; ). Subjects’ W judgements consistently
precede the production of the movement by about
300 ms. Interestingly, this is well after the onset of the
readiness potential, the negative potential arising from
movement by one second or more. On the basis of these
results, Libet concluded that, ‘‘The brain... decides to
initiate... or prepares to initiate the act at a time before
there is any reportable subjective awareness that such a
decision has taken place’’ .
Using a similar paradigm, Haggard and Eimer  asked
subjects to indicate the time at which ‘‘they first began to
prepare the movement’’ and related this to various com-
ponents of the readiness potential. In this study, subjects
moved either their left or their right index finger. The
onset of the lateralised readiness potential (occurring at
around 500 ms before the movement), rather than earlier
components of the readiness potential (starting more than
1 s before the movement), co-varied with the perceived
time at which preparation of the movement began. This
suggests that the awareness of preparing to move is
associated with the exact specification of the movement
(which finger will be moved) rather than some more
abstract representation of action, such as the goal of
A sense of agency
An important aspect of awareness of action is our sense of
agency; the feeling that we cause movements and their
consequences. In a recent study, Haggard and co-workers
[21??] investigated the consequences of a sensory event
being causally linked to a subject’s action. Subjects made
a key-press, which on some trials was followed 250 ms
later by an auditory tone. The subject’s task was to judge
the time at which they were aware of pressing a key or the
time at which they were aware of hearing a tone. When
their key-press caused a tone, subjects judged the timing
of their key-press as occurring about 15 ms later and the
tone as occurring 46 ms earlier than if the two events
occurred alone. This ‘temporal attraction’ seems to
depend on the perceived causal relationship between an
action and its sensory consequence(s). In a second experi-
ment, a varying delay (250, 450, or 650 ms) was introduced
between the key-press and the tone. Thefurther apart the
the tone to the key-press was diminished. Furthermore,
the temporal attraction between the perception of actions
and their sensory consequences did not occur when an
involuntary movement (caused by stimulating the motor
cortex using TMS) was followed 250 ms later by a tone, or
when subjects judged the timing of two causally related
external sensory events. The temporal attraction between
self-generated actions and their sensory consequences
binds together these events, and enhances our experience
If an explicit goal is suggested just prior to the action that
achieves that goal, then the action will be perceived as
intended. Wegner and Wheatley  have shown that
this can lead to errors in the perception of intention. A
Current Opinion in Neurobiology 2003, 13:219–224www.current-opinion.com
naive subject and a confederate simultaneously used a
single mouse to control the position of a pointer on a
screen. If the attention of the subject was drawn to an
object on the screen and the pointer stopped near that
object shortly afterwards, then the subject frequently
believed that s/he had intentionally moved towards the
object. In reality, his/her arm had been moved passively
by the confederate. As long as the action did not conflict
with some explicitly suggested goal then the action was
perceived as intended.
How do we recognise our own actions?
A clever paradigm that has been used to investigate self-
movement recognition involves subjects viewing the
can be manipulated so that the ownership of the hand is
that is either their own or the experimenter’s performing
movements that are either congruent or incongruent with
the subject’s own hand movements. Using this paradigm,
Daprati and co-workers  showed that normal subjects
confuse their own hand movements with those of the
experimenter about 30% of the time when the move-
ments are similar. Thus, even in an ambiguous situation
in which the experimenter’s hand makes the same move-
ments as the subject’s hand, the subject is able to recog-
nise their own hand movements 70% of the time, and
recognition is better for the dominant hand than the non-
dominant hand [24?].
A recent series of experiments by Knoblich, Prinz and co-
workers [25?,26?] has shown that subjects are adept at
recognising their own actions when they are played back
to them. In one study, subjects drew various characters,
and their movement patterns were recorded. A week later
they were presented with films of a moving dot, which
represented either their own pre-recorded movements or
the movements of someone else drawing the same char-
acter. Subjects were easily able to recognise which move-
ments were their own. Velocity seemed to be the crucial
component — self-movement recognition was not possi-
ble when the moving dot that represented their move-
ment was made to move at constant velocity while all
other factors remained the same as during the original
We are easily able to distinguish our own movements
from those of other people. How is this achieved, given
the overlapping neural system that is involved in the
part of the motor system is activated both when we
execute an action and when we observe a similar action
being executed [27–30,31?,32??,33]. If my brain ‘mirrors’
observed actions, how do I know that it is someone else,
and not me, who is moving when I observe an action?
Accumulating evidence indicates that the parietal cortex
plays a role in the distinction between self-produced
parietal cortex is activated when subjects mentally simu-
late actions from someone else’s perspective but not from
their own (Figure 1; [34?]). This region is also activated
when subjects observe their own actions being imitated
by someone else, but not when they imitate someone
else’s action [35?], and when subjects attend to someone
else’s actions rather than their own [36?,37]. It seems that
theinferiorparietalcortexisinvolved inclassifying move-
ments as external as well as in representing imagined
Confusing our own actions with other
The observation that patients with left parietal lobe
damage, with and without apraxia, are more likely to
confuse their hand movements with those of another
agent supports the idea that the parietal lobe is involved
in producing a sense of agency . Conversely, a recent
case study demonstrated that a patient with neglect and
somatoparaphrenic delusions caused by a right thalamic-
temporo-parietal lesion tended to deny that his left hand
was his own .
Certain psychiatric symptoms are characterised by an
inability to distinguish self- and externally produced
actions. Many patients with schizophrenia describe ‘pas-
sivity’ experiences in which actions, speech and thoughts
are controlled by some external agent rather than by their
own will. The experience of alien control could arise from
a lack of awareness of the predicted limb position [18,19].
Under normal circumstances, the awareness of initiating a
movement must depend on the predicted limb position,
because awareness of initiating a movement precedes the
actual movement and any feedback about actual limb
position (; see above). Patients with delusions of con-
trol are aware of their goal, of their intention to move and
of their movement having occurred, but they are not
to the problem of imagining movements, which we have
already discussed [17?].
Several studies have shown that patients that have delu-
sions of control confuse self-produced and externally
generated actions. Using the paradigm in which subjects
see feedback of their own hand movement or that of the
experimenter’s hand making similar movements, Daprati
and co-workers  found that schizophrenic patients
that have delusions of control are more likely than control
subjects to confuse their hand with that of the experi-
menter. Such people are less able to detect a discrepancy
between their movement and its consequences than
schizophrenic patients that do not have delusions of
control or control subjects. They become aware that a
movement is not their own when their movement and its
sensory (visual) consequences are discrepant spatially by
30 degrees or temporally by 300 ms, compared with 15
Self-awareness and action Blakemore and Frith 221
Current Opinion in Neurobiology 2003, 13:219–224
degrees and 150 ms, respectively, for control subjects
[4?]. One explanation for this is that the schizophrenic
patients that have delusions of control only have pro-
prioceptive and visual feedback to rely on for recogni-
tion, whereas control subjects are additionally able to
compare the sensory prediction with sensory feedback
from the movement.
Because a movement is predicted, its sensory conse-
quences can be perceptually attenuated relative to exter-
nal sensations . There is evidence that the confusion
between self and others in subjects with delusions of
control is a consequence of an abnormal sensory predic-
tion . Patients with delusions of control do not show
this perceptual attenuation of self-produced sensory sti-
mulation . The normal perceptual attenuation of the
sensory consequences of movement is accompanied by,
and might be attributable to, a reduction in activity in the
parietal operculum (secondary somatosensory cortex) and
the anterior cingulate cortex during self-produced tactile
stimulation compared with external tactile stimulation
. If delusions of control are associated with an impair-
ment in sensory prediction, we would expect to see no
attentuation of the activity in sensory regions. This was
precisely the result of a study in which schizophrenics
with and without delusions of control were scanned in
position emission tomography (PET) while they per-
formed a movement task (Figure 1; ). The presence
of delusions of control was associated with over-activity in
the right inferior parietal cortex. Moreover, activity in this
region returned to normal levels when the schizophrenics
were in remission. Over-activity of the inferior parietal
cortex might reflect a heightened response to the sensory
consequences of movements the schizophrenic patients
made during the scan, contributing to the feeling that
movements are externally controlled.
0 2040 60–20 –40–60–80 –100
Current Opinion in Neurobiology
Farrer & Frith 
Attribution of agency
Spence et al. 
Delusions of control
Blakemore et al. 
delusions of control
Weiller et al. 
Schematic diagram showing the lateral surface of a brain. Arrows indicate regions of parietal cortex that were activated by; the attribution of movement
to an external source for visually guided movements [34?], delusions of control in schizophrenia , hypnotically induced delusions of control
in the healthy brain  and passive movements .
Current Opinion in Neurobiology 2003, 13:219–224www.current-opinion.com
This result was supported by a recent study that inves-
tigated brain activity associated with delusions of control
self-generated movement to an external source in healthy
individuals. PET was employed to investigate the neural
correlates of active movements correctly attributed to the
self, compared with identical active movements misat-
tributed to an external source. Active movements attrib-
uted to an external source resulted in higher activations in
the parietal cortex and cerebellum than identical active
movements correctly attributed to the self. The brain
activations associated with the misattribution of active
movements resembled brain activity associated with pas-
sive movements (Figure 1; ). Together with the
results of Spence et al. , these results suggest that
of the cerebellar-parietal network.
We have briefly reviewed recent evidence that suggests
that many aspects of action occur without awareness. We
have argued that one aspect of an action that might be
available to awareness is the prediction of the sensory
consequences of that action. This prediction might
underlie the ability to distinguish between self-produced
and externally generated actions, a process that appears to
involve theparietal cortex.Thisbrainregion has also been
implicated in psychotic symptoms, in which patients
confuse their own actions with externally produced
actions. Future studies using new paradigms are needed
to elucidate the hypothesis that the forward model pre-
diction contributes to the awareness of action. In particu-
lar, the study of motor awareness in patients with poor
sensorimotor prediction might be fruitful in this context.
C Frith and S-J Blakemore gratefully acknowledge the support of the
Wellcome Trust UK. S-J Blakemore is supported by a Wellcome Trust
International Research Fellowship. Extract from ATONEMENT by Ian
McEwan. Copyright ? 2001 Ian McEwan. Published by Jonathan Cape, and
NanTalese/Doubleday. Used by permission of The Random House Group
Limited, and Alfred A Knopf, Canada.
References and recommended reading
Papers of particular interest, published within the annual period of
review, have been highlighted as:
? of special interest
??of outstanding interest
Wolpert DM, Ghahramani Z, Jordan MI: An internal model for
sensorimotor integration. Science 1995, 269:1880-1882.
2.Wolpert DM, Flanagan JR: Motor prediction. Curr Biol 2001,
3.Fourneret P, Jeannerod M: Limited conscious monitoring of
motor performance in normal subjects. Neuropsychologia 1998,
Franck N, Farrer C, Georgieff N, Marie-Cardine M, Dalery J,
d’Amato T, Jeannerod M: Defective recognition of one’s own
actions in patients with schizophrenia. Am J Psychiatry 2001,
In this study, subjects performed simple manual gestures while watching
visual feedback of their hand movements on a computer-controlled video
monitor.Parametric degrees of temporal and spatial discrepancies were
introduced between the subjects’ hand movements and the visual feed-
back. Control subjects noticed the discrepancy at a delay of approxi-
mately150 ms anda spatial mismatch of15 degrees. Incontrast, patients
with delusions of control were unaware of the discrepancy until a delay of
300 ms and a spatial discrepancy of 30 degrees.
5.Blakemore S-J, Frith CD, Wolpert DW: Spatiotemporal prediction
modulates the perception of self-produced stimuli.
J Cog Neurosci 1999, 11:551-559.
6.Libet B, Gleason CA, Wright EW, Pearl DK: Time of conscious
intention to act in relation to onset of cerebral activity
(readiness potential): the unconscious initiation of a freely
voluntary act. Brain 1983, 106:623-642.
7.Haggard P, Magno E: Localising awareness of action with
transcranial magnetic stimulation. Exp Brain Res 1999,
8.Jeannerod M, Frak V: Mental imaging of motor activity in
humans. Curr Opin Neurobiol 1999, 9:735-739.
9.Stephan KM, Fink GR, Passingham RE, Silbersweig D, Ceballos-
Baumann AO, Frith CD, Frackowiak RS: Functional anatomy of
the mental representation of upper extremity movements in
healthy subjects. J Neurophysiol 1995, 73:373-386.
10. Decety J, Perani D, Jeannerod M, Bettinardi V, Tadary B, Woods R,
Mazziotta JC, Fazio F: Mapping motor representations with
positron emission tomography. Nature 1994, 371:600-602.
This PET study demonstrated that verbal retrieval of action phrases is
associated with reactivation of the left ventral motor cortex and the left
inferior parietal cortex for actions that were either overtly or covertly
performed during encoding. Reactivation of the left dorsal parietal cortex
and the right cerebellum was restricted to actions that were originally
Nyberg L, Petersson KM, Nilsson LG, Sandblom J, Aberg C, Ingvar
M:Reactivationofmotorbrain areas duringexplicit memoryfor
actions. Neuroimage 2001, 14:521-528.
Naito E, Kochiyama T, Kitada R, Nakamura S, Matsumura M,
Yonekura Y, Sadato N: Internally simulated movement
sensations during motor imagery activate cortical motor areas
and the cerebellum. J Neurosci 2002, 22:3683-3691.
In this PET study, the neural correlates of an illusory wrist movement
elicited by tendon vibration was compared with motor imagery of the
same type of wrist movement. Motor imagery and the illusory kinesthetic
sensation activated a common network of contralateral motor areas and
the ipsilateral cerebellum. Together, these results suggest that it may be
the kinesthetic sensation during mental imagery that activates these
motor regions of the brain.
Subjects were presented with statements of bizarre or familiar actions,
and had to either perform or imagine those actions 24 h later, subjects
imagined performing a new set of actions, some of which had been
presented in the first session. Two weeks later, subjects were tested for
their memory of those actions. Actions that had been imagined in the first
two sessions were more likely to be classified as performed actions than
actions that had only been imagined in the first session. The more an
action is imagined, the more likely it is to be confused with a performed
Thomas AK, Loftus EF: Creating bizarre false memories through
imagination. Mem Cognit 2002, 30:423-431.
14. Gerardin E, Sirigu A, Lehericy S, Poline JB, Gaymard B, Marsault C,
and imagined hand movements. Cereb Cortex 2000,
15. Sirigu A, Duhamel JR, Cohen L, Pillon B, Dubois B, Agid Y:
The mental representation of hand movements after parietal
cortex damage. Science 1996, 273:1564-1568.
Normally there is a speed-accuracy trade-off for movements performed
bothin reality and in theimagination. Here, a subject with a righttemporo-
parietal lesion was tested on his ability to imagine and perform visually
guided arm movements. There was a relationship between the speed and
accuracyofhis visuallyguided actions, butnotbetweentheaccuracyand
Danckert J, Ferber S, Doherty T, Steinmetz H, Nicolle D, Goodale
MA: Selective, non-lateralized impairment of motor imagery
following right parietal damage. Neurocase 2002, 8:194-204.
Self-awareness and action Blakemore and Frith223
Current Opinion in Neurobiology 2003, 13:219–224
speed of his imagined movements. This result is interpreted as demon-
strating the role of the right parietal cortex in generating and updating
internal forward models of action.
This study demonstrated that patients with delusions of control do not
show the normal speed-accuracy trade off for imagined as for real
movements. These data support the notion that delusions of control
are associated with an abnormal internal representation of action.
Maruff P, Wilson PH, Currie J: Abnormalities of motor imagery
associated with somatic passivity phenomena in
schizophrenia. Schiz Res, in press.
18. Frith CD: The Cognitive Neuropsychology of Schizophrenia.
Hove: Lawrence Erlbaum Associates; 1992.
19. Frith CD, Blakemore S-J, Wolpert DM: Abnormalities in the
awareness and control of action. Phil Trans Roy Soc Lond: Biol
Sci 2000, 355:1771-1778.
20. Haggard P, Eimer M: On the relation between brain potentials
and the awareness of voluntary movements. Exp Brain Res
This paper reports an elegant series of experiments investigating the
awareness of actions and their sensory consequences. These experi-
ments demonstrated a temporal ‘binding’ effect between actions that
cause sensory stimuli (tones). This attraction between actions and their
consequences may be a possible mechanism for classifying sensory
events as self-generated.
Haggard P, Clark S, Kalogeras J: Voluntary action and conscious
awareness. Nat Neurosci 2002, 5:382-385.
22. Wegner DM, Wheatley T: Apparent mental causation – sources
of the experience of will. Am Psychol 1999, 54:480-492.
23. Daprati E, Franck N, Georgieff N, Proust J, Pacherie E, Dalery J,
Jeannerod M: Looking for the agent: an investigation into
consciousness of action and self-consciousness in
schizophrenic patients. Cognition 1997, 65:71-86.
The ability of right-handers and left-handers to recognise their own hand
movements was tested using a paradigm in which subjects saw on a
computer screeneither the visual feedback of their own hand movements
or the experimenter’s hand movements. When the experimenter panto-
mimed the subjects’ hand movements, thus producing an ambiguous
situation, subjects were more accurate in recognising their dominant
hand than their non-dominant hand. This is the first study to show that the
ability to recognise self-generated movements is affected by motor
Daprati E, Sirigu A: Laterality effects on motor awareness.
Neuropsychologia 2002, 40:1379-1386.
This study showed that subjects are adept at recognising their own
handwriting strokes when the stokes are played back to them, as long
as the strokes are replayed at the correct velocity.
Knoblich G, Prinz W: Recognition of self-generated actions from
kinematic displays of drawing. J Exp Psychol Hum Percept
Perform 2001, 27:456-465.
Knoblich G, Seigerschmidt E, Flach R, Prinz W: Authorship effects
in the prediction of handwriting strokes: evidence for action
simulation during action perception. Q J Exp Psychol A 2002,
Subjects observed parts of earlier self-produced and other-produced
writing strokes and were instructed to predict the following stroke. With
no constraints, subjects are better at predicting strokes of their own
writing than of other people’s writing. When the writing strokes were
made under constraints, however, the subjects were as good at predict-
ing other people’s writing strokes as their own. This was taken as
evidence for action simulation.
27. Grafton ST, Arbib MA, Fadiga L, Rizzolatti G: Localization of grasp
representations in humans by positron emission tomography.
2. Observation compared with imagination. Exp Brain Res 1996,
28. Decety J, Grezes J, Costes N, Perani D, Jeannerod M, Procyk E,
Grassi F, Fazio F: Brain activity during observation of actions.
Influence of action content and subject’s strategy. Brain 1997,
29. Grezes J, Decety J: Functional anatomy of execution, mental
simulation, observation, and verb generation of actions: a
meta-analysis. Hum Brain Mapp 2001, 12:1-19.
30. Iacoboni M, Koski LM, Brass M, Bekkering H, Woods RP, Dubeau
MC, Mazziotta JC, Rizzolatti G: Reafferent copies of imitated
actions in the right superior temporal cortex. Proc Natl Acad Sci
USA 2001, 98:13995-13999.
This study investigated the neural processing of the observation of real
hand movements and hand movements produced in three-dimensional
virtual reality. Only real actions in a natural environment activated a
visuospatial network including the right posterior parietal cortex. This
study suggests that the brain treats real and virtual hand movements
Perani D, Fazio F, Borghese NA, Tettamanti M, Ferrari S, Decety J,
Gilardi MC: Different brain correlates for watching real and
virtual hand actions. Neuroimage 2001, 14:749-758.
Buccino G, Binkofski F, Fink GR, Fadiga L, Fogassi L, Gallese V,
Seitz RJ, Zilles K, Rizzolatti G, Freund HJ: Action observation
activates premotor and parietal areas in a somatotopic
manner: an fMRI study. Eur J Neurosci 2001, 13:400-404.
In this fMRI study, subjects observed actions that were performed with the
mouth, the hand or the foot, and which did or did not involve an object.
different body parts, roughly representing the homunculus in premotor
cortex. The parietal lobe was activated when actions involved an object,
and again the activation pattern in this region was different for different
actions. This was the first study to demonstrate that action observation
activates parts of the motor system in a functionally specific manner.
33. Avikainen S, Forss N, Hari R: Modulated activation of the human
SI and SII cortices during observation of hand actions.
Neuroimage 2002, 15:640-646.
Subjects were scanned using PET while imagining actions either from
their own or from a third-person perspective. The parietal lobe was
activated by action simulation in the third person perspective.
Ruby P, Decety J: Effect of subjective perspective taking during
simulation of action: a PET investigation of agency.
Nat Neurosci 2001, 4:546-550.
The parietal cortex was differentially activated when subjects imitated the
experimentercompared with whenthe experimenter imitated the subject.
Decety J, Chaminade T, Grezes J, Meltzoff AN: A PET exploration
of the neural mechanisms involved in reciprocal imitation.
Neuroimage 2002, 15:265-272.
Subjects were scanned in PET while controlling a moving dot on a
computer screen. In some trials, subjects were in control of the dot’s
movement, whereas in other trials the dot was controlled by someone
else and moved along a different trajectory from the subject’s move-
ments.The parietal cortex was activated more whensomeoneelse wasin
control of the dot’s movement than during self-produced movements of
Farrer C, Frith CD: Experiencing oneself vs another person as
being the cause of an action: the neural correlates of the
experience of agency. Neuroimage 2002, 15:596-603.
37. Chaminade T, Decety J: Leader or follower? Involvement of the
inferior parietal lobule in agency. Neuroreport 2002,
38. Sirigu A, Daprati E, Pradat-Diehl P, Franck N, Jeannerod M:
Perception of self-generated movement following left parietal
lesion. Brain 1999, 122:1867-1874.
39. Blakemore S-J, Smith J, Steel R, Johnstone E, Frith CD: The
perception of self-produced sensory stimuli in patients with
auditory hallucinations and passivity experiences: evidence for
a breakdown in self-monitoring. Psychol Med 2000,
40. Blakemore S-J, Wolpert DM, Frith CD: Central cancellation of
self-produced tickle sensation. Nat Neurosci 1998, 1:635-640.
41. Spence SA, Brooks DJ, Hirsch SR, Liddle PF, Meehan J, Grasby
PM: A PET study of voluntary movement in schizophrenic
patients experiencing passivity phenomena (delusions of alien
control). Brain 1997, 120:1997-2011.
42. Blakemore S-J, Oakley DA, Frith CD: Delusions of alien control in
the normal brain. Neuropsychologia In press.
43. Weiller C, Juptner M, Fellows S, Rijntjes M, Leonhardt G, Kiebel S,
Muller S, Diener HC, Thilmann AF: Brain representation of active
and passive movements. Neuroimage 1996, 4:105-110.
Current Opinion in Neurobiology 2003, 13:219–224www.current-opinion.com