In my last post, I outlined an account of valuation. Whether mine is a good one is disputable, but the fact is that research in neuroeconomic, philosophy of mind, psychology, or any other field concerned with decision-making will sooner or later require a credible account of valuation, and value. Here is two reasons why.
First, there is a significant overlap between brain areas and processes in different valuations domains. While neuroeconomics, neuroethics and neuropolitics began to make explicit the neural mechanisms involved in these domains (Glimcher, 2003; Tancredi, 2005; Westen, 2007), attempts to cross-fertilize research are scarce. Research showed that economic, moral and political cognition involve similar brain processes. For instance, whether subjects play economic games (Rilling et al., 2002; Sanfey et al., 2003), reflect upon moral issues (Greene & Haidt, 2002; Koenigs et al., 2007) or make political judgments (Kaplan et al., 2007; Knutson et al., 2006; Westen et al., 2006), these tasks recruits principally the following evaluative mechanisms: Core affect, monitoring and control mechanisms described in my last post.
Second, even in one area--neuroeconomics--it is not clear what researchers mean when they talk about the "neural substrate of economic value". Take for instance two recent studies. Seo et al (2007) and Padoa-Schioppa (2007) both attempt to identify the brain valuation processes. The first one conclude that
The other discuss how the DLPFC contribute to decision-making:
A rich literature from lesion studies, functional imaging, and primate neurophysiology suggests that critical mechanisms for economic choice might take place in the orbitofrontal cortex. More specifically, recent results from single cell recordings in monkeys link OFC [Orbitofrontal Cortex] to the computation of economic value. We showed that the value representation in OFC reflects the subjective nature of economic value, and that neurons in this area encode value per se, independently of the visuo-motor contingencies of choice
individual neurons in the dorsolateral prefrontal cortex (DLPFC) encoded 3 different types of signals that can potentially influence the animal's future choices. First, activity modulated by the animal's previous choices might provide the eligibility trace that can be used to attribute a particular outcome to its causative action. Second, activity related to the animal's rewards in the previous trials might be used to compute an average reward rate. Finally, activity of some neurons was modulated by the computer's choices in the previous trials and may reflect the process of updating the value functions.
So how is something valuated? DLPFC or OFC ? How exactly they differ? Yes, one is about "reward" and the other "economic value", but again, since money can be rewarding and food can have an economic value (utility), it is not clear that different words refer to different processes. On top of that, there is also a huge literature on dopaminergic systems and valuation (see Montague et al, 2006; Montague, 2006) for a complete review). So some clarification is required here. I will try, in future post, do discuss these questions.
- Glimcher, P. W. (2003). Decisions, uncertainty, and the brain : the science of neuroeconomics. Cambridge, Mass. ; London: MIT Press.
- Greene, J. D., & Haidt, J. (2002). How (and where) does moral judgment work? Trends Cogn Sci, 6(12), 517-523.
- Kaplan, J. T., Freedman, J., & Iacoboni, M. (2007). Us versus them: Political attitudes and party affiliation influence neural response to faces of presidential candidates. Neuropsychologia, 45(1), 55-64.
- Knutson, K. M., Wood, J. N., Spampinato, M. V., & Grafman, J. (2006). Politics on the Brain: An fMRI Investigation. Soc Neurosci, 1(1), 25-40.
- Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushman, F., Hauser, M., et al. (2007). Damage to the prefrontal cortex increases utilitarian moral judgements. Nature, 446(7138), 908-911.
- Montague, P. R., King-Casas, B., & Cohen, J. D. (2006). Imaging valuation models in human choice. Annu Rev Neurosci, 29, 417-448.
- Montague, R. (2006). Why choose this book? : how we make decisions. New York: Penguin Group.
Padoa-Schioppa, C. (2007). Orbitofrontal Cortex and the Computation of Economic Value. Ann NY Acad Sci, annals.1401.1011.
- Rilling, J., Gutman, D., Zeh, T., Pagnoni, G., Berns, G., & Kilts, C. (2002). A neural basis for social cooperation. Neuron, 35(2), 395-405.
- Sanfey, A. G., Rilling, J. K., Aronson, J. A., Nystrom, L. E., & Cohen, J. D. (2003). The neural basis of economic decision-making in the Ultimatum Game. Science, 300(5626), 1755-1758.
- Seo, H., Barraclough, D. J., & Lee, D. (2007). Dynamic Signals Related to Choices and Outcomes in the Dorsolateral Prefrontal Cortex. Cereb. Cortex, 17(suppl_1), i110-117
- Tancredi, L. R. (2005). Hardwired behavior : what neuroscience reveals about morality. New York: Cambridge University Press.
- Westen, D. (2007). The political brain : the role of emotion in deciding the fate of the nation. New York: PublicAffairs.
- Westen, D., Blagov, P. S., Harenski, K., Kilts, C., & Hamann, S. (2006). Neural Bases of Motivated Reasoning: An fMRI Study of Emotional Constraints on Partisan Political Judgment in the 2004 U.S. Presidential Election. J. Cogn. Neurosci., 18(11), 1947-1958.