Measuring plasticity with MRI in humans

Giorgia Silani, Claus Lamm, Tania Singer

Frontiers in Social Neuroscience and Neuroeconomics

Ways to measure it in vivo (in humans)Ways to measure it in vivo (in humans)

Mechanisms of neuroplasticityMechanisms of neuroplasticity

What is ‘plasticity’ and (why) is it important?

Mental training of compassion – feedback and discussionMental training of compassion – feedback and discussion

(plastos) - ‚capable of being molded‘Neuroplasticity:

the capacity of the nervous system to modify its organizationchanges in the structure and function of the brain as a result of experience

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)

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 payfor it)

Goals of neuroplasticity research: identifywhich behaviors can be changedhow they can be changedwhen they can be changed

important: developmental aspects

Lenroot & Giedd, Neurosci Biobehav Rev 2006 Huttenlocher & Dabholkar, J Comp Neurol 1997

Neuroplasticonomics?

decision making:complex behavior, requiring basic perceptual, cognitive, affective, social, and motor skills

All these aspects can be trained and shaped

Neuroplasticonomics?Public goods game and training to cooperate?

Increased motivation to cooperate

replaces necessity of punishment?

Ubiquitous phenomenon in daily lifeSensory and motor representations – clinical aspects

recovery after stroke Anton Räderscheidt, recoveringfrom hemispatial neglect

Sensory and motor representations – clinical aspectsNeural reorganization in sensory deprived people (blind, deaf)

Büchel al., Brain 1998

Letter Reading: sighted

Braille reading: blind

‚Visual‘ activity in auditory cortex in deaf people

Finney et al., Nature 2001

neuroplasticity in complex motor-skills

Pantev et al., Ann NY Acad Sci 2001(adapted from Elbert, Science 1995)

Pascual-Leone et al., Annu Rev Neurosci 2005

hMT/V5

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

Changes in „connectivity“ between neuronsHebbian learning: „cells that fire together, wire together“Substrate: synaptic modifications

Ramón y Cajal, 1911

Spines

Enriched environments and synaptogenesis

Johansson & Belichenko, J Cereb Blood Flow Metab 2001

Effects of living in enriched environmenton number of synapses

Standard environment Enriched environment

‚spontaneous‘ synaptogenesis (and elimination)

Trachtenberg et al., Nature 2002

no specific training or intervention!

Neuronal plasticity is fundamental property of nervous systemBrain is less ‚hard-wired‘ as we (used to) thinkmainly 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

General considerationsStructural changes

Morphometry – grey matterDiffusion-tensor Imaging (DTI) – white matter

Functional changesfMRI

Functional segregation/localizationEffective connectivity (DCM)

intervention

‚Control‘

Time 1 Time 2

Intervention: short-term vs. long-term

McGonigle et al., NeuroImage 2000

General considerations Challenges

reliability of measurementscross-sectional: selection effects

Effect of training or was he better to begin with?

General considerations Challenges

reliability of measurementscross-sectional: selection effectsinterventional: drop-outs/compliance

Draganski et al., Nature 2002

General considerationsStructural changes

Morphometry – grey matterDiffusion-tensor Imaging (DTI) – white matter

Functional changesfMRI

Functional segregationEffective connectivity (DCM)

General considerationsStructural changes

Morphometry – grey matterDiffusion-tensor Imaging (DTI) – white matter

Functional changesfMRI

Functional segregationEffective connectivity (DCM)

Functional changes – fMRI ‚localization‘‚conventional‘ approach – intervention-related differencesExample: effects of ‚meditation training‘ on attention

Cross-sectional design

Brefczynski-Lewis et al., PNAS 2007

Response to distractor sounds

vs.

Areas associated with goal-directed attention more active in expertsAreas associated with self-related thought more active in novices

Changes in effective connectivity – the idea From localizing assessment of changes (where? How much?)to changes in (mechanistic) interaction between brain areas

(„how“)

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?

Changes in effective connectivityIncidental learning of co-occurence of two stimuli (sound and visual

stimulus) modeled using Rescorla-Wagner model

Den Ouden et al., Cereb Cortex 2008

Distractors have probabilistic relationship that can be (incidentally) learnedfor example:

p = 0.8

p = 0.2

Changes in effective connectivityIncidental learning of co-occurence of two stimuli (sound and visual

stimulus) modeled using Rescorla-Wagner model

Surprise-related activation

Changes in effective connectivityIncidental learning of co-occurence of two stimuli (sound and visual

stimulus) modeled using Rescorla-Wagner modelEff. connectivity between auditory and visual areas

Surprise upregulates V1No-surprise downregulates it

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?

Summarystructural 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?

SummaryNeuroplasticity 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‘?

How does prolonged mental training of compassion affect individual and social behavior?

Does it have positive effects on prosocial behavior (cooperation, helping, altruism)?

Basic design: interventional, three groupscompassioncompassion

trainingtraining

emotion emotion regulationregulation

controlcontrol(memory)(memory)

timetime

‚group retreat‘

individual training

individual training (cont‘d)

T1T1(pre)(pre)

T2T2 T3T3 T4T4(post)(post)

T5T5Follow-upFollow-up

Methods/levels of observation: psychoneuroendocrinologybehaviorneural (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?