Zusammenfassung der Ressource
Delusion of agency, control and ownership
- appropriate behaviour and stable experience depend
on being able to discriminate between internal thoughts
and actions and those produced by an external source
- the brain doesn't automatically know the difference
- self and other
- Jeanerrod 2003 -
mechanism by which own
actions are distinguished
from others is critical
- delusions of
agency = self
monitoring errors
- self processing concepts
Anmerkungen:
- self processing concepts: action/agency/intention, autobiographical memory, self in imagery and memory, depersonalisation, language and self, social self
- the self
- a set of ideas, beliefs,
mental representations
and models about who we
are
Anmerkungen:
- some representations of our self are explicit and available for conscious introspection - intentions, feelings, body image. other representations are implicit - subconscious schemas which cannot be consciously inspected
- Agency
- mechanisms that tell you that you are
the author of your own
actions/intentions/thoughts
- to distinguish between self and other - self monitoring
Anmerkungen:
- Szechtman 1998 - internal source monitoring system where inappropriate activation may be involved with internal thoughts being experienced as coming from an external source. E.g. to be alien from self - lose sense of agency over thoughts/inner speech/intentions
- the self and agency
- agency covers many factors
Anmerkungen:
- agency covers many factors: thinking about action, intention to act, executing actions, receiving feedback. these all draw on different underlying systems all of which can go wrong and lead to various forms of delusions. acting is not a unitary phenomena - all aspects have separate neural substrates.
- Gallagher 2000
- need a sense of ownership and a sense
of agency - being aware of action and
being aware that they are responsible for
acting
Anmerkungen:
- reflex actions - action is beyond consciousness - no intention to move.
sense of ownership and sense of agency usually coincide but can dissociate - dissociation can be caused by TMS.
- Delusions of agency
- alien control
Anmerkungen:
- alien control - alien hand syndrome, thought control, thought insertion, thought withdrawal
- alien hand syndrome
Anmerkungen:
- alien hand syndrome - see limbs move but it feels like it is being controlled by an alien force. lose sense of intention to move but not ability. not always a transient phenomena
- symptoms associated with schizophrenia in
which patients misattribute self generated
actions to an external source (Blakemore
2003)
Anmerkungen:
- Schizophrenia: thoughts/speech/actions influenced or replaced by those of external agents. lost feeling of agency and ownership
- Schneider 1959 - first
rank symptoms of
schizophrenia
- Frith 2000 - experiences due
to a lack of awareness of
intended actions
Anmerkungen:
- if intention is separated from action then it appears as though the action doesn't belong to you
- passivity phenomena
Anmerkungen:
- passivity phenomena - not in control of thoughts and actions - someone else is controlling
- auditory hallucinations
- insights from eye movements
- everytime a saccade
occurs, image on the
retina changes
dramatically
- yet we retain a stable image of the world
- Van Helmhotzl 1867
Anmerkungen:
- Van Helmhotzl - muscles invovled in moving the eye send a message to the brain which allows brain to compensate for the change and keep the image stable. sends an efferent copy
- Van Hoist 1954
Anmerkungen:
- Van Hoist 1954 - when sending motor commands to move the eye the motor areas of the brain send a parallel efference copy to visual areas. this predicts sensory consequences (corollary discharge) of the movement which is used to compensate for retinal displacement during eye movements . motor areas tell perceptual area that any disturbance is due to eye movement and not the world moving so compensation is made and we do not see the fragmented world shown on the retina.
- corollary
discharge = the
brain detects
predicted sensory
outcomes and
compensates the
resulting
perception.
sensory prediction
Anmerkungen:
- corollary discharge notion has been applied to self produced actions and self monitoring. Firth - we have an internal model of motor control that normally allows us to recognise the sensory consequences our actions
- Forward model of delusions of agency
- Miall 1993 - forward model of motor control
- sensations from actions compared
with internal mental model of action in
order to establish agency
- if model matches action related sensory signals then action is attributed to the self
- if there is a discrepancy between sensory signals and
model of predicted consequences then action is attributed
to someone else
- forward dynamic component
- makes predictions about the next state
of the system and compares this with
the desired state
- helps formulate action appropriate to intention
- forward output component
- predictions of sensory
consequences of movement
compared with actual sensory
consequences of movement -
needs access to efferent copy
- the forward model and delusions of alien control
- discrepancy in comparison between predicted and
actual sensory consequences cancel out reafferant
inputs and be used to distinguish between self
produced and externally produced signals.
- forward output model is impaired - cannot
generate an accurate prediction if no
access to efferent copy
- leads to large sensory discrepancy
which leads to self produced action
feeling as if it was externally produced
- action you wanted performed, aware of intention
but not aware of initiating action or aware of its
predicted sensory consequences = fells as if
actions are made by an external force
- supporting evidence - why can't you tickle yourself?
Anmerkungen:
- Blakemore 1998/1999/2000 why can't you tickle yourself?
subjects rated sensation of a tactile stimulus and looked at the perceptual effects from altering the correspondence between self generated movement and sensory consequences. employed delays between left arm movement and right arm stimulation. as delay increased tactile stimuli perceived as more likely to feel like its someone else. as discrepancy increases the efferent copy becomes inaccurate, Blakemore 1999 - self produced sensation less intense than when produced by a robot.
self generated action has predicted consequences and so the brain makes allowances for the consequences of the action. externally generated actions cannot be attenuated as they are unexpected and therefore the movement feels more intense. when the prediction of self generated movement is lost, then the actions are not attenuated and so feel like someone else produced them.
- Frith 2000
Anmerkungen:
- frith 2000 - sensory discrepancy large in schizophrenics so own actions are always experienced as coming from an external source. schizophrenics shouldn't show usual patterns with self tickling
- Blackmore 2000
Anmerkungen:
- Blakemore 2000 - patient study of self monitoring. looked at schizophrenics with and without passivity and hallucination and normal controls asked to rate perception of a tactile sensation on left palm, sensation either self or externally produced. perception not modulated by self generated actions in patients with hallucinations/passivity. internally generated sensations rated as more intense therefore must be from an external source.
- delusions of passivity in the normal brain
- Blakemore 2003
Anmerkungen:
- Blakemore 2003 - ideo motor movements in PET study using hypnotised normal subjects. idea motor movements = unconscious (ougie boards). subjects had arms attached to a pulley system when in PET scanner. Active movement of arm, real passive movement, deluded passive movement (told pulley would move arm but it didn't - arms still moved). Deluded passive movement seen as highly involuntary - claimed they were not responsible for movement. cerebellum had more diffuse activity for deluded passive movement and significant activation. partial cortex had more activity in DPM, involvement makes it feel externally generated. - use of hypnotisable subjects = highly suggestible
- identical movements are
processed different depending
on whether they are attributed to
the self or to an external source
- network involving cerebellum and
parietal cortex - overactivity may
underlie misattributions
- other accounts
- Spence 1996
Anmerkungen:
- Spence 1996 - problem to do with timing of awareness - if aware of consequences before aware of predicted outcome then this is not normal experience of self generated actions and so must be external
- Jeannerod 1992/2003
Anmerkungen:
- Jeannerod - delusions are due to a dysfunction in a representational system dedicated to coding third person information
- Firth and Blakemore - the motor
system does make provision for
internalising actions and intentions
of others
- Jeannerods theory
- Stimulation theory (1994/2003)
Anmerkungen:
- Stimulation theory - observer builds a model of the actions they see which can be used to under the intentions of another. actions of others represented to same extent as own actions so need to be distinguished. constant question - them or me?
- the who system
Anmerkungen:
- the who system - different representations for different aspects of monitoring. conscious judgments about movements are dependent on a 3rd person representation system whereas control of movement is dependent on 1st person info. delusions of control can be explained by failing to monitor 3rd person signals that enable them to make judgments about their own actions.
- shared representations and the who system
Anmerkungen:
- shared representations and the who system: specific mechanisms exist that are responsible for the active attribution of action to another agent or the self. certain components of these self other systems overlap which can cause delusions of agency. if we see another performing an action we have a representation of it but are aware that it is someone else performing the action. in schizophrenics the overlap between self/other systems is much larger - they have a problem with shared representations. they cannot distinguish between own actions and representations of others actions
- agency and the who system
Anmerkungen:
- the who system is responsible for discriminating between self generated action and action of others. mechanism is depended on shared and overlapping representations - can become dysfunctional in pathology and psychosis
- Evidence
- Ruby 2001
Anmerkungen:
- Ruby 2001 - brain imaging study on actions from different perspectives. 1st person perspective - inferior parietal lobe activation. 3rd person perspective = activation in symmetrical area in rh. distinct and overlapping systems involved in processing action - observers can represent others actions and thus can infer mental states of others by drawing on own representations. 3 systems - what, where, who
- doesn't necessarily go against forward model
- Mirror neurons
Anmerkungen:
- mirror neurons - found in monkeys - unethical to look for them in humans. fire during a self generated movement and when seeing another perform an action.
- premotor theory of attention
Anmerkungen:
- pre motor theory of attention - actions and motor prep take place when observing actions. system is involved in understanding actions, with links to theory of mind. the motor area is always ready to act
- Phantom limb syndrome
- delusion in body limb ownership
Anmerkungen:
- phantom limb syndrome - perception of a limb that no longer exists.
- deafferentation
Anmerkungen:
- deafferentation - certain brain areas no longer receive feedback so old representations can no longer be used. leads to dramatic changes in somatosensory map.
In Phantom limb this process has become dysfunctional and the brain is still relying on old representations
- neural remapping
Anmerkungen:
- neural remapping - Ramachandren 1997 - synchronous stimulation of an object and unseen body part can make you feel as if sensation is coming from object. suggestive of a highly fluid sense of self ownership and body representation. remarkable level of neural plasticity in adult brain
- rubber arm illusion
Anmerkungen:
- rubber arm illusion - visual info updates body representations when trying to interpret somatosensory stimulation.
Botnivick 1998 - the first
Ehhrsson 2007 - threatening a rubber hand produces an anxious response - stabbing movement, compared brain response. anxiety responses in bilateral insula and bilateral ACC. relationship between vividness of illusion and anxiety response - implies feeling of ownership so strong it replaces real limb. (compared to stabbing movements to real hand)
- very simple manipulations
can confuse the brain on
things it has held certain for
years