lecture 8- the mirror neuron system Flashcards
(26 cards)
what type of neurons are mirror neurons?
motor neurons
what does it mean when we say the motor cortex has a topographical map of our body?
different neurons within the motor cortex generate activity or contraction in muscles in different areas of our body
lateral activity (ventral -> dorsal) = contraction of tongue, face, hands, trunk
medial activity = rest of leg, toes
what is most of the motor cortex dedicated to moving?
face/lips/tongue/hands/fingers (important for manipulating and communicating)
what does it mean that M1 neurons are topographically arranged?
neighbouring neurons activate neighbouring muscles
NOTE: M1 neurons cross pathways so that activity in right M1 results in movement in single muscles of left side of body
where are premotor cortex neurons located?
in F5 region (lateral)
when do mirror neurons fire?
respond during execution of a goal-directed action- different mirror neurons generating different coordinated actions
ALSO are visual neurons- respond to sight of other people performing the same goal-directed action
what study did Rizzollatti (1996) carry out on monkeys?
specific hand actions performed by monkey vs. live actions by experimenter
-> rastagram and peristimulus histograms (line = when hand touches raisin (action))
certain cell responds to sight of action (experimenter doing it- visual response)
AND when monkey does it itself (no response when using tweezers)
what is meant by the action specificity of mirror neurons?
respond during specific actions AND someone else doing that specific action (e.g once cell responds to anticlockwise twisting rotation)
how do mirror neurons respond to face actions?
- same as normal actions- e.g grasping with teeth, sucking, eating, teeth chattering
- when performs and when someone else doing
- shows close match between motor representation and visual representation of action
how do mirror neurons respond to hidden actions?
- many respond when late part of action is out of sight
- typically do not respond to miming (pretending to do action)
- (Milton, 2001)- response comes on when hand is in contact with object (miming version = reduced response) -> SAME WITH OCCLUDER
- monkey knows object is behind occluder, and sees had disappearing behind
- respond when knowing outcomes of a specific action
- not purely visual- represent knowledge that an action is taking place
what do STS neurons respond to?
- selectively to range of actions- moving faces, hands, interacting with objects
- also integrate sight and sound of actions so respond to selective sounds of actions
- no one has found mirror neurons in STS yet (no motor response)
what does the mirror neuron system look like in monkeys?
STS = respond to sight and sounds
IPL = respond to sight and sound but do show motor responses (does have mirror neurons)
F5 (IFG) = respond to sight, sound and execution of actions
system: reciprocal interconnections between inferior parietal lobe and inferior frontal gyrus, receives input from STS
what does TMS of the motor cortex show in humans?
causes motor evoked potentials (MEPs) in muscles- MEPs provide metric of motor system activity
increased visual input leads to increased activity in motor system (premotor and M1)
SO during TMS activation of motor cortex, action observation increases likelihood of MEPs
what happens to MEPs during action observation?
- MEPs are enhanced during action observation
- watching hand actions increases MEPs in hand (action specificity)
- sounds also increase likelihood of MEPs
- listening to words that use the tongue enhance MEPs in the subject’s tongue
(shows mapping of words onto the circuits used to generate them)
where did Mukamel (2010) find evidence of mirror neurons?
supplementary motor area (SMA) and hippocampus
what did Hamilton (2004) and Jacobs & Shiffrar (2005) find about the perception of actions?
- executing an action changes perception (lifting heavy object while looking at normal object, looks light to them) AND observers walking on a treadmill found it difficult to judge biological motion walker speed
why do we need mirror neuron system for understanding actions?
- active when we execute an action
- we understand the actions we’re doing (we know our goals, intent)
- have MNS activity when we perceive others actions too
- so therefore we can understand their actions
what is simulation theory?
to understand other people’s actions, we simulate their actions using our motor systems
why do we need mirror neurons for touch?
- there are somatosensory neurons that respond during touch and observing another person being touched (different neurons code touch in different places- not visual, somatosensory mirror neurons)
- mechanoreceptors in skin feedback to the brain that you are not being touched so don’t actually feel touch
- but can block this by nerve in brachial plexus using- sodium channel blocker (injection)
- results in literally feeling touch- skin provides barrier between yours and other peoples minds
what did Lacoboni (2005) find about mirror neurons being responsible for understanding action intension?
- way to underatand actions is by understanding intentions (comes from combo of action and context)
- greater activity in premotor cortex to an intention condition compared to action alone
- shows mirror neurons are responsible for understanding intention of observed action
- can make sense of action if know context
what does Liberman’s (1993) motor theory of speech state?
language evolved from understanding from the MNS- mirror neurons represent actions for imitation and understanding
so are are a link between sender and receiver
-> this is necessary pre-requisite for any form of communication
F5 in monkey is responsible for hand and mouth movements (homologue of Broca’s area in humans- speech area)
what do Arbib & Rizzolatti (1998) suggest about link between actor and observer?
- when actor acts, observer will recognise the action and the actors intention
- the development of the observers ability to consciously control their MNS results in ability to emit a voluntary signal
- leads to primitive dialogue between them (new use for MNS, as inital intentional communication was based on hand movements and oro-facial gestures)
what can deficits in the MNS lead to?
MNS likely to play important role in social cognition -> social cognition deficits may result from MNS dysfunction?
what is the evidence that impaired MNS performance underlies ASD?
- local thinning in cerebral cortex of areas of MNS (STS, IPL, IFG) and ASD severity correlated with cortical thinning
- reduced Mu rhythm suppression in ASD (Mu rhythm = index of motor activation) during observation of actions
- reduced TMS-induced corticospical activation during action observation
- (in children) reduced MNS response to observation and execution of facial expressions in IFG
