W6: Mirror Neurons Flashcards
(14 cards)
What are mirror neurons?
A class of neurons that become active when individuals perform a specific motor act, mirroring the behaviour of the person performing the act
What is the standard for identifying mirror neurons?
Single unit recordings- requires opening of the skull and implanting a recording electrode
What are the benefits of single unit recordings?
Microelectrodes are placed close to the cell, which allows the ability to record intracellularly
What is a limitation if single unit recordings?
They are very invasive as it requires opening the skull
Where does the first evidence of mirror neurons come from?
Rizzolatti’s lab- investigated mirror neurons in monkeys
Found that some neurons in the area of a monkey’s premotor cortex fired when the monkey reached for or bit a peanut. Electrodes were used to record activity whilst giving the monkeys different objects to handle. Motor neurons started to fire when monkeys were handed an object and these were the same neurons that fired when a monkey grasped the peanut, finding that individual neurons only responded to v specific actions. Mirror neuron would fire when a monkey grasped a peanut, and the same neuron would also fire when an experimenter grasped a peanut, similarly to a different neuron firing only when a monkey put a peanut in their mouth + experimenter did the same
What area in the brain is believed to have direct control over the movement of voluntary muscles and play a role in the understanding of others?
Premotor cortex, especially the F5 area
What did Rizzolatti find about specific neurons when measuring auditory mirror neurons in macaque monkeys?
Neuron 1: responded to vision and sound of a tearing action (paper ripping)- sound of the same action performed out of the monkeys sight was equally effective. Sounds that were non action related did not evoke any excitatory response
Neuron 2: responded to vision and sound of a hand dropping a stick- response was also present when monkey heard the sound of the stick hitting the floor. Non action related arousing sounds did not produce reaction
Neuron 3- when the monkey heard the peanut breaking and saw it, the neuron was activated highly but this was not the same effect for paper ripping
How did Rizzolatti measure auditory mirror neurons in macaque monkeys?
A total of 497 neurons were recorded in 3 macaque monkeys- the authors studied the auditory properties by using sounds produced by the experimenters actions e.g. peanut breaking, paper ripping, and non action related sound e.g. white noise, clicks and other animal calls.
In another group, they used digitalised related action sounds were the monkey could not see the action occurring but could hear the action. Some were sound only, vision only etc.
Variety of visual + sound conditions e.g. just S, just V or both
What were Rizzolatti’s overall findings when measuring auditory mirror neurons in macaque monkeys?
A neuron makes a mirror neuron when it is active both when the animal engages in an activity and when the animal observes or hears the experimenter engage in the same or closely related activity
Area F5 contains a population of audio-visual mirror neurons that discharge not just to the execution of observation of a specific action but also when this action can only be heard
1/3 of these neurons are ‘strictly congruent’, meaning they require a close match in action production and perception, whereas 2/3 are broadly congruent and respond to actions with the same goal but different movement specifics
How did Mukamel et al (2010) measure mirror neurons in humans?
Reported on experiments using single unit recordings in humans- electrodes were implanted as a prelude to surgery for epilepsy rather than primarily for research, so the location of electrodes was not selected to test various hypotheses
Patients were asked to do two actions, either involving watching video clips of a cup on its own or a hand holding a cup, OR they would actually do what the video did i.e. hold the cup themselves
Face experiment condition- ppts either observed pictures of happy/sad faces or would see the word smile and then mimic this
Recorded 1177 neurons in diff areas of the brain
What did Mukamel et al (2010) find when measuring mirror neurons in humans?
When the action was to do with precision grapsing e.g. holding a cup, the firing was significant, but not particularly for frowning or smiling. Confirms that in humans, just watching the action leads to activation but this is not shown in response to stimuli of faces.
Some neurons did however respond more to facial expressions as opposed to hands
Across diff neurons, there is activation in response to different actions
How did Iacoboni et al (2005) aim to investigate the neural basis of intention in humans?
Half of ppts received implicit instructions and the other half received explicit instructions
All ppts were placed in the MRI- essentially trying to see how mirror neurons respond to the context, action or intention, and the types of intention/if this makes a difference
Overall- 3 types of videos- context video (showed a scene with objects), action video- showed a hand grasping a cup with no context, and intention video- showed the action in two diff conditions (drinking and cleaning up) Drinking context suggested that the hand was grasping the cup to drink whereas the cleaning context suggested that the hand was grasping the cup to clean up- thus the only condition which contained additional information was the intention condition
What did Iacoboni et al (2005) find when investigating the neural basis of intention in humans?
Large increases in neural activity were observed in occipital, posterior, temporal, parietal and frontal areas for observations of the action and intention conditions. Context shows slightly different activations
Intention condition had significant signal increases compared to the action condition- in visual areas which is expected given the presence of objects in the intention condition but not in the action condition.
Explicit group had higher activation than implicit on left frontal lobes due to greater effort required by the explicit instructions but not significant differences across the stimuli
What were the main take away findings from Iacoboni et al (2005) when investigating the neural basis of intention in humans?
Overall findings showed an increased activity of the right IFC for the intention condition, suggesting that the mirror neuron area actively participates in understanding intentions behind observed actions
