A Neuroeconomic Approach to Understanding Valuation of Risky

Prospects

Neal HinvestUniversity of Bath

U.K.

What is neuroeconomics?

NEUROECONOMICS

ECONOMICSNEUROSCIENCE/

BEHAVIOURALNEUROSCIENCE

PSYCHOLOGY

Valuation of outcomes• How we make the best

decisions in the face of incomplete information?

• Every outcome entails cost, therefore, all choices are economic decisions

• All outcomes are processed (at or below conscious level) to maximise potential benefit taking into account potential loss

• Valuations are occurring at every moment of our lives

• Choice behaviour is based upon these valuations

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Valuation and the brain• To create valuations, “cold” and “hot”

information must be integrated• The dopamine system has been identified

as having a major role in reward processing• Important role in reward-prediction learning

(Montague et al, 1996; O’Reilly et al, 1999; 2002)

• The dopamine system projects through the striatum to the frontal cortex

• Dorsal striatum = action selection and reward prediction

• Ventral striatum = stimulus-response learning (for recent review see Hikosaka et al, 2008)

• PFC = integration centre for top-down control (Miller & Cohen, 2001)

• Damage to prefrontal regions leads to dysfunction of valuation mechanisms such as perseveration of a single action over time and incapacity to maintain a goal online

• Plausible candidate for “valuation signal” is orbitofrontal cortex (Elliot et al. 2003; Knutson et al. 2001; O’Doherty et al. 2001; Bush et al., 2002)

What will be the impact of such research?

• Identify mechanisms involved in specific aspects of human choice behaviour, and thus provide models of decision-making processes with biological validity

• Answer key questions within economics and psychology (e.g. McClure et al, 2004)

• Understand how possible alteration of the function of valuation mechanisms may underlie problematic behaviours (e.g. drug/gambling abuse)

Our research

• Understanding neural substrates of valuation of risky prospects

• Present potential gains and potential losses

• Participants actively ascribe a personal worth to the prospect

• Functional Magnetic Resonance Imaging (fMRI)

Results – potential reward

• Valuation of potential rewards is associated with increased activity within bilateral OFC

• Activation also measured in fronto-parieto-occipito networks

P < .001 (uncorrected)

Results – potential loss• Valuation of potential

losses is associated with activity in medial frontal regions extending from ventral OFC through VMPFC to dorso-medial PFC

• Activity also measured in fronto-parieto-occipto networks

P < .001 (uncorrected)

P < .001 (uncorrected)

Conclusions

• Increased evidence for OFC as having a major role in valuation

• Possible source of signal integration• Suggestion of spatiotopic role of OFC in

reward/loss processing (Elliot et al, 2000 ; Ursu et al, 2005; O’Doherty et al, 2003: medial = reward, lateral = loss)

Evidence for altered function of OFC in psychiatric samples

• Pathological gamblers and drug abusers exhibit evidence of biased valuation mechanisms that place larger worth on addiction-related cues

• This has been associated with dysfunction within dopamine-fed systems, most importantly, the prefrontal cortex

• Presented substance abusers and

pathological gamblers with a delay discounting task

• Outcomes are presented for 3s, then participant is free to choose

Results• Drug abusers and pathological

gamblers exhibit hyper-activation of a similar region of lateral dorsal OFC compared to controls when evaluating outcomes

• This occurred even though there were no significant differences in choice behaviour

• Represents existence of increased neural ‘effort’ to maintain behaviour at comparable levels to non-addicted groups (Padula et al, 2007)?

Pathological gamblers

Substance abusers

Conclusions

• Increased evidence for role of OFC in valuation of risky outcomes

• Possible existence of two overlapping systems for valuation of potential rewards and potential losses

• Evidence for altered function of OFC in addiction-disordered groups (underlie biased valuations?)

AcknowledgementsUniversity of BathAlan Lewis John Cullis

University of WarwickGemma Calvert

University of ExeterTim Hodgson

University of OxfordRob Rogers

University of ManchesterIan AndersonRebecca ElliottShane McKie