Measuring plasticity with MRI in humans

1. Frontiers in Social Neuroscience and Neuroeconomics Measuring plasticity with MRI in humans Giorgia Silani, Claus Lamm, Tania Singer

2. Overview What is ‘plasticity’ and (why) is it important? Mechanisms of neuroplasticity Ways to measure it in vivo (in humans) Mental training of compassion – feedback and discussion

3. What is ‚plasticity‘? • plastos (plastos) - ‚capable of being molded‘ • Neuroplasticity: • the capacity of the nervous system to modify its organization • changes in the structure and function of the brain as a result of experience

4. Why is it relevant? • Intrinsic aspect of the (human) nervous system: „plasticity is not an occasional state, but the normal ongoing state throughout the lifespan“ (Pascual-Leone et al., 2005)

5. Why is it relevant? • interface of nature and nurture • ‚equipment‘ with a basic machinery • ‚meets‘ environments acting on that machinery (or not) • ‚use it or lose it‘ (you can always get it back later, if you are willing to pay for it)

6. Why is it relevant? • Goals of neuroplasticity research: identify • which behaviors can be changed • how they can be changed • when they can be changed important: developmental aspects Lenroot & Giedd, Neurosci Biobehav Rev 2006 Huttenlocher & Dabholkar, J Comp Neurol 1997

7. Why is it relevant - for us? • Neuroplasticonomics? • decision making:complex behavior, requiring basic perceptual, cognitive, affective, social, and motor skills • All these aspects can be trained and shaped

8. Why is it relevant - for us? • Neuroplasticonomics? Public goods game and training to cooperate?  Increased motivation to cooperate replaces necessity of punishment?

9. Examples of neuroplasticity • Ubiquitous phenomenon in daily life • Sensory and motor representations – clinical aspects • recovery after stroke Anton Räderscheidt, recovering from hemispatial neglect

10. Examples of neuroplasticity • Sensory and motor representations – clinical aspects • Neural reorganization in sensory deprived people (blind, deaf) Letter Reading: sighted ‚Visual‘ activity in auditory cortex in deaf people Braille reading: blind Finney et al., Nature 2001 Büchel al., Brain 1998

11. Examples of neuroplasticity • neuroplasticity in complex motor-skills hMT/V5 Pantev et al., Ann NY Acad Sci 2001(adapted from Elbert, Science 1995) Pascual-Leone et al., Annu Rev Neurosci 2005

12. The dark side • The dark side of neuroplasticity ... Elbert et al., Neuroreport 1998 + various perceptual deficits in deaf and blind participants + lack of plasticity in highly trained skills + decline of plasticity across the lifespan

13. Mechanisms • Changes in „connectivity“ between neurons • Hebbian learning: „cells that fire together, wire together“ • Substrate: synaptic modifications Spines Ramón y Cajal, 1911

14. Mechanisms • Enriched environments and synaptogenesis Effects of living in enriched environmenton number of synapses Standard environment Enriched environment Johansson & Belichenko, J Cereb Blood Flow Metab 2001

15. Mechanisms • ‚spontaneous‘ synaptogenesis (and elimination) no specific training or intervention! Trachtenberg et al., Nature 2002

16. Mechanisms – Summary • Neuronal plasticity is fundamental property of nervous system • Brain is less ‚hard-wired‘ as we (used to) think • mainly based on changes of synapses (synaptogenesis & elimination) • Persistent and temporary changes have to be taken into account as an inherent property of the system(s) we investigate

17. Measuring neuroplasticity in vivo • General considerations • Structural changes • Morphometry – grey matter • Diffusion-tensor Imaging (DTI) – white matter • Functional changes • fMRI • Functional segregation/localization • Effective connectivity (DCM)

18. Measuring neuroplasticity in vivo • General considerations • Study designs • cross-sectional (study existing groups) • interventional/longitudinal (change across time) Intervention: short-term vs. long-term intervention ‚Control‘ Time 1 Time 2

19. Measuring neuroplasticity in vivo • General considerations • Challenges • reliability of measurements (and trait?) McGonigle et al., NeuroImage 2000

20. Measuring neuroplasticity in vivo • General considerations • Challenges • reliability of measurements • cross-sectional: selection effects Effect of training or was he better to begin with?

21. Measuring neuroplasticity in vivo • General considerations • Challenges • reliability of measurements • cross-sectional: selection effects • interventional: drop-outs/compliance

22. Measuring neuroplasticity in vivo • General considerations • Challenges • reliability of measurements • cross-sectional: selection effects • interventional: drop-outs/compliance • constraints on number of measurements – adequate sampling of ‚plasticity-curve‘? Draganski et al., Nature 2002

23. Measuring neuroplasticity in vivo • General considerations • Structural changes • Morphometry – grey matter • Diffusion-tensor Imaging (DTI) – white matter • Functional changes • fMRI • Functional segregation • Effective connectivity (DCM)

25. Measuring neuroplasticity in vivo • General considerations • Structural changes • Morphometry – grey matter • Diffusion-tensor Imaging (DTI) – white matter • Functional changes • fMRI • Functional segregation • Effective connectivity (DCM)

26. Measuring neuroplasticity in vivo • Functional changes – fMRI ‚localization‘ • ‚conventional‘ approach – intervention-related differences • Example: effects of ‚meditation training‘ on attention Response to distractor sounds Cross-sectional design vs. Brefczynski-Lewis et al., PNAS 2007 • Areas associated with goal-directed attention more active in experts • Areas associated with self-related thought more active in novices

27. Measuring neuroplasticity in vivo • Changes in effective connectivity – the idea  From localizing assessment of changes (where? How much?) to changes in (mechanistic) interaction between brain areas („how“) 

28. Measuring neuroplasticity in vivo • Changes in effective connectivity – the idea • Rejection of unfair offers un ultimatum game (Knoch et al.) : Connectity between rDLPFC and mOFC Modulation by ‚fairness-training‘? ‚self-interest‘ training?

29. Measuring neuroplasticity in vivo • Changes in effective connectivity Incidental learning of co-occurence of two stimuli (sound and visual stimulus) modeled using Rescorla-Wagner model Distractors have probabilistic relationship that can be (incidentally) learned for example: p = 0.8 p = 0.2 Den Ouden et al., Cereb Cortex 2008

30. Measuring neuroplasticity in vivo • Changes in effective connectivity Incidental learning of co-occurence of two stimuli (sound and visual stimulus) modeled using Rescorla-Wagner model Surprise-related activation

31. Measuring neuroplasticity in vivo • Changes in effective connectivity Incidental learning of co-occurence of two stimuli (sound and visual stimulus) modeled using Rescorla-Wagner model Eff. connectivity between auditory and visual areas Surprise upregulates V1 No-surprise downregulates it

32. Measuring neuroplasticity in vivo • Changes in effective connectivity – the idea • Rejection of unfair offers un ultimatum game (Knoch et al.) : Connectivity between rDLPFC and mOFC Modulation by ‚fairness-training‘? ‚self-interest‘ training?

33. Measuring neuroplasticity in vivo • Summary • structural and functional neuroplastic changes can be assessed using MRI/fMRI and a variety of other methods (EEG/ERPs, TMS, behavioral ...) • Variety of challenges and open questions • On level of methods – what do/can they measure? • On level of mechanisms – what changes? How much change is possible? How much change is spontaneous?

34. Measuring neuroplasticity in vivo • Summary • Neuroplasticity approach as a complement to ‚lesion‘ model: train (‚add‘) function instead of disturbing it  insights into function of system • Interface nature-nurture: combine with genetics and pharmacological interventions • Basic question: how plastic is the human mind? • Scientific question: from ‚how does it work‘ to ‚how can we change the way it works‘?

35. Discussion How does prolonged mental training of compassion affect individual and social behavior? Does it have positive effects on prosocial behavior (cooperation, helping, altruism)?

36. Discussion Basic design: interventional, three groups compassion training emotion regulation control (memory) ‚group retreat‘ individual training individual training (cont‘d) T1 (pre) T2 T3 T4 (post) T5 Follow-up time

37. Discussion Methods/levels of observation: psychoneuroendocrinology behavior neural (fMRI) well-being, ... Tasks - changes in ... Individual behavior in non-social and socials contexts? Social/prosocial behavior?  What would convince/be of interest for economists?