Lecture 1 - Mirror Neurons Pt1 PDF

Lecture 1 - Mirror Neurons Pt1 Assessment In Class Test (40%) 12 Nov, 9am 2 x 250 words essays Lab classes In-Class MCQ exam (60%), week 14/15 Mirror Neurons First found in monkeys 2 monkeys One picked up banana, one watched Same neurons fire in both monkeys  A...

Lecture 1 - Mirror Neurons Pt1 Assessment In Class Test (40%) 12 Nov, 9am 2 x 250 words essays Lab classes In-Class MCQ exam (60%), week 14/15 Mirror Neurons First found in monkeys 2 monkeys One picked up banana, one watched Same neurons fire in both monkeys  Amount of papers on mirror neurons throughout the years Overview Introduce MNS Macaque studies Human Studies Do humans have mirror neurons? Broken mirror theory of autism MNS as a tool for action understanding The Macaque Mirror Neuron System ** Kilner & Lemon (2013) ** More than 800 papers published Only 25 empirical papers reporting MN or MN-like neurons in macaque First reported in F5, but also in parietal regions 15/25 papers studies neurons in F5 30% of neurons recorded in F5 showed mirror properties Different classes of (39/184) ‘visually complex’ neurons: 12 = respond for exact match between performed and observed 6 = these neurons also fired to observing other visually similar (non-identical actions) 11 = fired when the observed action was logically related to the executed action. E.g. when observing food being put on the table and also when grasping the food to put in the mouth (they code for the meaning/goal of eating the food!) 10 = fired during observed movements but NOT during executed movements The fact that mirror neurons do not fire when there is no object (and therefore no goal), could be taken as evidence that they encode something to do with the goal of the action. ** ** Action understanding “Mirror Neurons are the basis of action understanding” Rizzolatti & Craighero (2004) “the parieto-frontal mechanism allows an individual to understand the actions of another individual ‘from the inside’ and gives the observing individual a first-person grasp of the motor goals and intentions of another individual.” Rizzolatti et al. (2010) 3 classes of mirror neurons Strictly congruent (31.5%) – exact match between observed and executed action Broadly congruent (60.9%) - Responded to observed actions that were similar to the executed actions Non-congruent (7.7%) – no clear relationship between observed and executed actions Testing Action Understanding Lesions in the mirror neuron system, should impact action understanding. Rizzolatti & Craighero (2004) not necessarily because the MNS is widespread, and so it is difficult to lesion it without producing “more general cognitive deficits.” Also “other mechanism [outside MNS] may mediate action recognition” Instead we can look for evidence that MNs represent the goal of an action. Audio-visual Mirror Neurons  Some neurons in macaque premotor cortex responded to the sound of paper ripping (but not white noise) The other sound that recruited many neurons was the sound of a peanut breaking Kohler et al. (2002)  Recorded activity from 497 neurons in macaque premotor cortex. –63 neurons (13%) discharged both when the monkey performed a hand action and when they heard an action related sound. –They further investigated 33 neurons that responded to action sounds. 22 neurons responded in the same way for the sound and the observation (visual representation) of the action. What about if a grasp is only inferred? ‘In this experiment the authors reasoned that if mirror neurons are involved in action understanding then they should discharge also in conditions where the monkey does not see the action but has sufficient information to form a representation of an action” Umilta et al. (2002)  Recorded activity from 220 neurons in macaque premotor cortex. –Main conditions: full vision condition and hidden condition for both real (object-oriented) and pantomimed actions (actions with no objects). –103 mirror neurons. – 37 that gave good enough recordings in all conditions. –These neurons responded for object-oriented actions in both the fully visible and the hidden conditions. Embodiment of tools  After training, MNs (F5) start to respond to grasping with pliers The same neurons code for grasping with both normal and reverse pliers MNs code for the goal of the action, not the action kinematics “This single-neuron recording study provides crucial evidence that the ventral premotor cortex (area F5) encodes the goal of motor acts.” Summary: Action understanding in Macaques MNs respond to both the observation of an action and execution of the action They do NOT respond for pantomimed actions (actions with no object, and therefore no goal) MNs do not only respond to seeing an action, they can also respond to hearing the outcome (goal) of that action MNs also fire even when you can not see the grasp, but have reason to believe that it happened (you know that the object is behind the blind) Summary Neurons in monkey F5 respond to both action observation and execution. –Strictly congruent; broadly congruent; non-congruent Many MNs respond depending on the goal of the action not on the precise action Inferior parietal regions also contain MNs Superior temporal sulcus (STS) also important in action observation Human MNS Similar areas contain MNs in humans and monkeys But evidence for MNs in humans is mostly indirect (as difficult to perform single-neuron recordings) EEG/MEG evidence of human MNS  Early evidence (Cohen-Seat et al., 1954; Gastaut & Bert, 1954) shows evidence of EEG mu rhythm suppression to both observed and active movements. Confirmed by other recent studies (see Rizzollati et a., 2014). ** Mu Suppression ** Fadiga et al. (1995) TMS pulses over primary motor cortex M1 MEPs recorded MEPs significantly increased during the conditions in which subjects observed movements. Humans activate for both goal and meaningless actions Observation in 4 conditions: Grasping. Object. Arm Movement. Dimming Detection DC, extensor digitorum communis; FDS, flexor digitorum superficialis; FDI, first dorsal interosseus; OP, opponens pollicis  Motor Evoked Potentials during observation of object grasping, or meaningless actions. Compared to control tasks or detecting dimming light, or viewing 3D objects. Larger MEPs for both action conditions compared to control. Human MNS seems to activate for both goal-directed and meaningless actions (unlike monkey MNS). This may be why humans imitate, whereas other animals do not? (Rizzolatti et al., 2004) fMRI studies  Clear clusters in IFG (F5), IPL (PF/PFG). Clusters also observed in sensory, limbic, and cerebellar regions. Only 30% of studies included both action execution and action observation conditions. Do Humans Have Mirror Neurons? Monkey research showed very complex assortment of neurons in each area. So maybe the area codes for both things but there are no neurons with “mirror properties”? fMRI / EEG not sensitive enough to detect these different classes of neurons. Many fMRI studies do not include an action condition, but just assume MNs from activation of “motor areas”. Single neuron evidence of Mirror Neurons in humans Although these were recorded in supplementary motor area as well as hippocampus and parrahippocampal gyrus (electrode placement was determined for clinical purposes). Human MNS - Summary Indirect evidence of MNs in humans from fMRI, TMS and EEG. Single-neuron studies confirm the presence of neurons with mirror properties. Human MNS extends beyond “classic” motor areas. Human MNS responds to both object-directed and meaningless actions. Action understanding in humans “Thus, premotor mirror neuron areas—areas active during the execution and the observation of an action—previously thought to be involved only in action recognition are actually also involved in understanding the intentions of others. To ascribe an intention is to infer a forthcoming new goal, and this is an operation that the motor system does automatically.” Iacoboni et al. (2005) 6 different videos: –3 (Context only, Action, Action in Context) x 2 (Before tea, After tea) design. Greater activity in IFG in the intention condition than action condition –Since both conditions included an action, this suggests that MNs respond more when the intention behind the action is known. Also showed differential activity in IFG between the two different intentions –MNs encode the intentions. Summary Overwhelming evidence for mirror neurons in monkeys. Lots of indirect evidence for mirror neurons in humans. Many mirror neuron studies frame their research in terms of mirror neurons being involved in action understanding. #PS495