Does the Brain Matter on Choice Behavior?

a Neuroeconomic Perspective

Ruey-Ming Liao

Department of Psychology

National Cheng-Chi University

Taipei, Taiwan, China

E-mail: rmliao@nccu.edu.tw

Abstract- Along with the development of methodology andtechnique progressing in neuroscience, it is now a turning pointfor neuroscience to move one more step forward with researchaims to investigate how brain does for behavior requiredhigher cognitive functions. Choice behavior is not only acomplex behavior for single individual but also involvedthoroughly for people living in the social environment.Recent work in neuroscience reveals the neural basis of choiceor decision-making initially based on the brain dopaminesystems, which mediating reward motivation and otherrequired cognitive processes. As the choice behavior highlylinks to economic activity in our society, it is worth to study thebrain mechanisms behind choice or decision making in acurrent trend now so-called the neuroeconomics. Despite inits infant stage, the study of neuroeconomics is promising toprovide a better answer for the brain does matter on choicebehavior.

I. INTRODUCTIONTo survive and adapt in the environment, human beings

and/or living organisms have to exert choice behavior withsophisticated decision-making or computation indynamically responding to various types of current andin-coming stimuli. Human choice behavior is thus socomplex that cannot be revealed from the study of anysingle discipline. Choice behavior is not only apsychological issue involved with cognitive informationprocess but also an economical topic embraced bymathematical model. With benefits apparently generatedfrom reunification of both psychology and economics forseveral decades, it is now expected to gain more heuristicinsight from biological realm. In the past few years, aresearch subfield now noticed as neuroeconomics has beenrolled with increasing momentum [1].

In terms of economics, human choice behavior isestablished on the basis of rational model ofdecision-making. It is assumed that people calculatefinancial decision with ration and/or self-interest tomaximize monetary benefit. However, this assumption hasbeen challenged and disproved by Kahneman and Tversky[2], whose studies arguing the existence of irrational choice

Nai-Shing Yen

Department ofPsychology

National Cheng-Chi University

Taipei, Taiwan, China

E-mail: nsy@nccu.edu.tw

on uncertain situation. Although one of the underlyingmechanisms for argument is relevant to emotion andmotivation domains, it has not been focused until morerecently as a renaissance of interest on emotion inpsychology and neuroscience. Thus, the issue regarding howemotion is get involved in choice behavior has beenincreasingly focused. For a broaden economic activities inour society, research in the emerging field, neuroeconomics,aims to reveal how the brain works for business transaction,negotiating, bargaining, investing, and others.

II. NEUROSCIENCE METHODSThe knowledge of basic finctions of the brains of

human and other mammals is always accumulated alongwith the development of methodology and techniqueprogressing in neuroscience. Many different methods areused at the current stage. Each has strength and weakness.Animal study is widely used for the basic research on anyspecific topic. Despite the shortage of necessitatedinvasiveness, animal brains can be deliberately damaged andstimulated as compared to human's. In electrophysiology,electrical signals recorded from polygraph on various partsof body can represent physiological reactions on central andperipheral nervous system, such as electroencephalogram(EEG) and electrocardiogram (ECG). Recently, neuralimaging instruments without any invasion on the braintissue known as functional magnetic resonance imaging(fMRI) and positron emission topography (PET) provide agreat leap forward on measuring brain activity in livingsubjects. In addition, on clinical, data collected frmcomparing normal subjects and individuals diagnosed withneuropsychological deficits (i.e. Parkinson's disease anA4depression) are informative and valuable. Currently,research work in neuroeconomics is highly relied on usingthese methods as described to reveal more solid fundamentalmechanisms for choice behavior and other relevanteconomic activities.

III. REWARD AS THE BASIC DRIVE

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Despite several approaches potentially available, oneway to study the mechanisms of choice behavior is based onthe cost/benefit analysis. From the adaptive aspect,individual normally responds to obtain reward to meet thesurvival needs, which may further contain psychologicalsatisfaction. To avoid the aversive condition that leads toexperiencing punishment is also true for this case. Thatreinforcing effects of these behavioral outcomes aremediated by the mesolimibic dopamine systems is stronglysupported by animal studies done in the past three decade [3,4]. Although human's reward-related behavior has beenstudied less extensively due to inefficient equipment in thepast, it is now possible with neural imaging techniques andwith comparable data available. Detected by fMRI, themajor terminal areas of mesolimibic dopamine systemsincluding the nucleus accumbens, the amygdala, and medialprefrontal cortex, are significantly activated by certainclasses of rewarding stimuli such as appetitive food andpsychostimulant drugs [5]. In addition to the naturalreinforcercers and drugs, the case is also true for abstractreward like monetary reinforcer and social approval.Despite the existence of distinct brain site(s) specificallyunderlying for each type of reward, the circuitry connectingthe aforementioned areas is recognized as a basic neuralsubstrate critically involved for processing thereward-related behavior. Thus, in terms of motivation, anybehavior process can be initially driven by activating thisneural circuit when individual facing a stimulus withrewarding property. Accordingly, with the operationaldefinition of behavioral neuroscience or experimentalpsychology, the rewarding stimulus will be able to increasethe likelihood ofthe behavior.

IV. BRAIN DOPAMINE AND COGNITIONIf one is motivated to exert behavioral responses, the

next step may need to concern about how to organize orallocate these behavioral outputs. This step is importantfor two reasons: 1) to make the individual utilize the limitedphysiological resource from body and brain in a moreefficient manner, and 2) to lead for a better way onenvironmental adaptation. Cognitive informationprocessing is then necessary to encounter with issue. Themesolimbic dopamine systems are not only involved inprocessing the reward itself but also participated inregulating several fundamental cognitive processes [6].Experimental studies show that selective lesions ofdopamine-related areas in rats or primates can actuallyproduce cognitive deficits on attention, learning, andmemory. Comparable cognitive impairments also appearin human subjects suffered with brain dopamine dysfunction,such as Parkinson's disease, schizophrenia, and attentivedeficit hyperactive disorder (ADHD) in children. Thatdopaminergic drugs, agonists and antagonists,correspondently ameliorate these cognitive deficits furthersupport the argument of dopamine as a powerful regulatorof different aspects of cognitive brain functions from

pharmacological perspective. Thus, maintaining the braindopamine in a homeostatic state is a key to run basiccognitive processes in harmony that would certainly helpindividual doing a better job on higher cognitive functionslike decision-making or choice.

Frontal lobes of the brain have long been recognized asthe most important site for mediating the higher cognitivefunctions [7]. In regarding the decision-making,accumulating evidence from recent efforts involvingneuroimaging, neuropsychological studies, animal workindicate that the prefrontal cortex serves as the neuralsubstrate of decision-making [8]. Several subprocessesassociated to decision-making have been defined andmatched to the subareas of the prefrontal cortex, which isnow known to be heterogeneous in neural structure andfunction. In general, the orbitofrontal cortex is associatedto deal with incentive gain, best-guess estimations, and theemotional reaction under gains and losses. Thedorsolateral prefrontal cortex tends to be involved inoperating decision information on-line and in consciousdeliberation during decisions, while the anterior cingulate isinvolved in conflict processing with the outcome followingdecision. Moreover, the rule-based decision andself-generated information are linked to the frontopolarcortex.

V. RECENT STUDIES RELEVANT TO NEUROECONOMICSStudies in neuroscience give a new way to look at

human mind. It also provides us new evidence to rethinkabout many concepts of economics. For example, asmentioned above, the brain dopamine systems are active fora wide variety of rewards, such as drugs, food, and money.It means that money can be directly rewarding.Traditionally, the utility of money is supposed to be indirectand should be derived from direct utilities of goods that arepurchased with money. Furthermore, a common principlein economics is that the utility of money depends on thevalue of it, and is independent of the source of it. However,it was found that earned money is more rewarding thanunearned money. Greater activity was detected in thestriatum (also a major terminal area of the dopaminesystems) when subjects earned money rather than justreceiving equivalent money without effort [9].

In real life, people always face to make choice inuncertain or risky situation. The insula cortex is reported todeal with the ambiguity of risky choice. fMRI imagingshowed that the insula cortex was differentially activatedwhen people chose certain money amounts rather thanambiguous gambles [10]. Risky choice is highly involvedwith interplay of cognitive and affective processes. Howdoes the brain respond to the immediate and delayedgratification? Using fMRI, McClure et al. [11] found thatthe emotionally responsive limbic system was active whensubjects chose immediate rewards, and the lateral prefrontaland posterior parietal cortex was more active when subjectschose delayed but larger rewards. A series of work done

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by Damasio and his colleagues found that patients suffering behavior for single individual but also it involves thoroughlyprefrontal damage (ventromedial prefrontal cortex in for people in the socially living environment. As theparticular) made choices that yield higher short-term choice behavior highly links to economic activity in ourrewards but higher long-term punishment [12]. It is then society, it is worth to study the brain mechanisms behindsuggested that the subjects with ventromedial prefrontal choice or decision making in a current trend now so-calledlesions are insensitive to future consequences. the neuroeconomics. Despite in its infant stage withFurthermore, Dickhaut et al. [13] found more activity in the hurdles to overcome, the study of neuroeconomics isventromedial prefrontal cortex when subjects thought about promising to provide a better answer for the brain doesgains compared to losses, and more activity in inferior matter on choice behavior.parietal and cerebellar areas when subjects thought aboutlosses. In addition to these neural imaging data drawing a REFERENCESlarger scale profile on cortices for this type of choice, [1] P. Glimcher and A. Rustichini, "Neuroeconomics: the consilience of brainelectrophysiological fdings further confined the neural and decision", Science, vol. 306, pp. 447-452, 2004

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