Monday, March 18, 2013

Neural processing of rewards in different modalities takes place in the same way (in humans) – An Evidence hook

See ‘notes’ below for what is an evidence hook?

Chib, V.S., Rangel, A., Shimojo, S. and O’Doherty, J.P. (2009) Evidence for a Common Representation of Decision Values for Dissimilar Goods in Human Ventromedial Prefrontal Cortex. The Journal of Neuroscience. Vol 29(39) pp.12315–12320. [Publisher link - may be behind paywall] [DOI: 10.1523/ JNEUROSCI.2575-09.2009]
Abstract: To make economic choices between goods, the brain needs to compute representations of their values. A great deal of research has been performed to determine the neural correlates of value representations in the human brain. However, it is still unknown whether there exists a region of the brain that commonly encodes decision values for different types of goods, or if, in contrast, the values of different types of goods are represented in distinct brain regions. We addressed this question by scanning subjects with functional magnetic resonance imaging while they made real purchasing decisions among different categories of goods (food, non-food consumables, and monetary gambles). We found activity in a key brain region previously implicated in encoding goal-values: the ventromedial prefrontal cortex (vmPFC) was correlated with the subjects’ value for each category of good. Moreover, we found a single area in vmPFC to be correlated with the subjects’ valuations for all categories of goods. Our results provide evidence that the brain encodes a “common currency” that allows for a shared valuation for different categories of goods.
Comments: Common neural activity for different categories of rewards (food, non-food consumables, monetary gambles). 

McNamee, D. Rangel, A., and O’Doherty, J.P. (2013) Category-dependent and category-independent goal-value codes in human ventromedial prefrontal cortex. Nature Neuroscience, advance on line publication. [Readcube version - I'm not sure whether there's a risk of a paywall[doi:10.1038/nn.3337]
Abstract: To choose between manifestly distinct options, it is suggested that the brain assigns values to goals using a common currency. Although previous studies have reported activity in ventromedial prefrontal cortex (vmPFC) correlating with the value of different goal stimuli, it remains unclear whether such goal-value representations are independent of the associated stimulus categorization, as required by a common currency. Using multivoxel pattern analyses on functional magnetic resonance imaging (fMRI) data, we found a region of medial prefrontal cortex to contain a distributed goal-value code that is independent of stimulus category. More ventrally in the vmPFC, we found spatially distinct areas of the medial orbitofrontal cortex to contain unique category-dependent distributed value codes for food and consumer items. These results implicate the medial prefrontal cortex in the implementation of a common currency and suggest a ventral versus dorsal topographical organization of value signals in the vmPFC.

Notes: This paper seems to raise the evidential bar appreciably over previous work, including the Chib et al (2009) paper listed above. I’d be rather surprised if this paper did not turn out to represent the ‘state of the art’ on this issue for the first half of 2013. This paper defends a far more narrow and specific claim than many others that will appear on this list (or ‘hook’), and I’ll discuss it in more detail later, as well as include it in the hooks for narrower claims about neural valuation in humans.


Entries on this page will be to papers specifically claiming to show that the neural processing of rewards in different modalities (in humans) either does or does not take place 'in the same way'. This formulation is deliberately vague so that I can cast the net wide. As I go along I'll identify more restricted theses, and document them separately.

This is the first of a collection of 'evidence hooks'. Together the hooks will form an evidence rack. (What I’ll do here is inspired by a suggestion of Peter Suber’s – see this posting on Common Currencies, and this document by Peter Suber.)

I’m going to figure out how to work with the evidence hook/evidence rack idea as I go along, and it may take a while before I’ve settled on stable procedures.

Version history

First version posted - 2013/03/18.
Minor update - 2013/03/22.

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