Modeling and Imagery: Intro

1. Modeling and Imagery: Intro Wilson & Knoblich, 2005

2. Conspecifics? • The case for motor involvement in perceiving conspecifics • The idea that we use a part of motor cortex to interpret the movements of others of our species • Starts with the notion that other people are special (perceptually), because they can be directly compared with ourselves (& they’re the only thing that can be)

3. Perceiving people • Generates motor representation • But no movement • So why have a movement plan without movement? • Purpose? • It’s proposed here it’s for an emulator • This is something that in computer hardware/software terms enables programs intended for one device to run on others • Perhaps the motor plan enables us to predict other’s actions

4. Covert imitation of actions • Chameleon effect • Facial expression (cinema, the nodder) • Gestures & body sway (mothers/babies, launderette, bar) • Tone of voice, pronunciation (Janet & Corinne) • Ever watched a sport you play and experienced that you are “playing” yourself?

5. Covert imitation of actions • Automaticity of imitation • Stimulus-response compatibility • Responses fastest when cue matches response • Suggests motor programs for response are best cued by watching the same or similar action • Which in turn suggests imitation is automatic

6. Covert imitation of actions • Neonate imitation • One-month olds • Mouth opening, tongue protrusion, facial expression of emotion, blinking, vowel sounds, /m/ sound… • “Slightly older” • Tongue protrusion to side, more consonants

7. Covert imitation of actions • Frontal lobe damage •  Loss of inhibition •  Automatic tendency to imitate • (evidence for covert but inhibited imitation in the rest of us)

8. Covert imitation of actions • Mirror Neurons • Previous examples: overt imitation • This example: covert imitation exists when overt behavior is absent • These neurons (in premotor cortex of monkey) fire both when acting and when watching action Diagram shows activity in both premotor and parietal areas

9. Covert imitation of actions • Mirror Neurons • Previous examples: overt imitation • This example: covert imitation exists when overt behavior is absent • These neurons (in premotor cortex of monkey) fire both when acting and when watching action • Note: this is in monkeys, not humans, but the idea is that perhaps we also have imitative circuitry in our brains

10. Covert imitation of actions • Activation of motor planning areas in humans • Observation of other’s body movement (finger, hand, arm, mouth, foot) leads to activation of motor cortex • Only occurs for plausible movements • Also occurs for complex movements…more so for those who are expert in the activities • Heard sounds promote activation of hand parts of motor cortex

11. Covert imitation of actions • Activation of motor planning areas in humans • Observation of other’s body movement (finger, hand, arm, mouth, foot) leads to activation of motor cortex • Implies new mappings can be learned • Mappings can be from different stimuli (don’t have to be matched, e.g. hand for hand) • Thus music can be “heard” as movement, provided you are familiar with the required movement

12. Covert imitation of actions • Facilitated muscle activity • Trace EMG activity found in response to watching same limbs of others move • Motor related brain rhythms • Rhythms blocked by motor activity are also blocked by observation • Suggests equivalence of perceived and performed action

13. Why do we covertly imitate? • Might be due to the need for action understanding… • To assist in categorizing the action • To uncover the purpose behind the behavior • To understand the antecedents of the action (why do this? Affective state) • Makes sense if both sensory and motor consequences are initiated • Might be something to do with language evolution • Area F5 & Broca’s area

14. Why do we covertly imitate? • …or we might be trying to perceive what we are seeing • Serves as an “emulator” • Can perhaps be used to fill in missing or scratchy information • Can perhaps be used to project likely movements of other’s body even when unsighted • Info must permeate other systems beyond the motor system for this to work p. 464

15. Why do we covertly imitate? • Contrasts w/other (previous) proposals • Others “postdictive”, this is predictive • This requires allocentric representation of body • Can map something watched in 3rd person as experienced in 1st person • Clear tie ins for modeling, no? p. 464

16. Perception is predictive • Your favorite CD/playlist • Similar prediction has been shown in movement perception • “Representational momentum” • Forward shift accepted, backward rejected (explain) – p. 465 has further examples • Suggests perceptual extrapolation • “Filling in” – the x-y example • Also found for human movement (point light)

17. Perceptual Prediction & Emulation • How does it work? • Internal model – forward model (Jordan) • Avoids dependence on feedback (important when considering chronometry) in ballistic movements

18. Perceptual Prediction & Emulation • How does it work? • Emulators (again) • See definition on p. 466 • Model of external system run internally, in real time • Implies information about external world can be had before it occurs • Emulation easier for simple patterns, or for very familiar patterns • Supported by the idea that when outcomes are unpredictable, representational momentum is absent (rock bouncing down hill)

19. Motor involvement in perceptual prediction • There must be a match between what is seen and what is experienced (what is experienced is what builds the emulator) • In the case of watching human bodies, the match is pretty good – we have one, so we “know” how it behaves • Does covert imitation get used for perceptual prediction in human movement?

20. Motor involvement in perceptual prediction • Motor activation that precedes the related perceptual event • Pianists generate motor imagery prior to the event that relates to it • Motor activation of a finger used to play a note occurs prior to the note being heard in a familiar piece of music

21. Motor involvement in perceptual prediction • Predictive capabilities of mirror neurons • Mirror neurons that fire to a hand grasp of an object also fire when the hand is seen about to grasp when going behind a screen…but only if it is known there is an object behind the screen

22. Motor involvement in perceptual prediction • Influence of motor learning on perception • When a particular movement pattern is learned, subsequent recognition of similar movement patterns improves

23. Motor involvement in perceptual prediction • Superior perceptual prediction by viewing oneself • Idea here is that if the internal model is based on an estimation of the external reality, then it should be best when the external reality is one’s own! • And it is borne out • People watching themselves perform better in point light task identification then those watching others

24. Motor involvement in perceptual prediction • Superior visual judgment for possible movements • Perceptual prediction is influence by motoric knowledge

25. So, um, what? • Internal emulators imply perceptual sophistication of unparalleled complexity • That these are unconscious implies there is a lot going on of which we are not aware • That the events invoke motor imagery is really important…see next week’s audio slides