Automatic integration of confidence in the brain valuation signal :: Mael Lebreton, Raphaelle Abitbol, Jean Daunizeau & Mathias Pessiglione :: Nature Neuroscience, Vol. 18, No. 8, August 2015 :: www.nature.com/neuro
Summary and review of the above paper
The ventromedial prefrontal cortex is the brain region most associated with ratings of the relative value of stimuli. Subjects are seen as assigning subjective values to the potential outcomes of possible actions leading to valuable results. A growing body of evidence suggests that such valuations are encoded in the ventromedial prefrontal cortex.
These neural value signals are capable of rating items that have no common scale; thus such as cars, food, faces and paintings may be rated by the same type of signal, but have nothing specifically in common with one another. The brain seems to generate these values even when they are not part of an on going task. These value signals are viewed as guiding subsequent behaviour.
Confidence in valuations
This valuation theory is now well established, but the Lebreton paper suggests that the ventromedial could also encode how confident subjects are of their ratings of stimuli. The suggestion is that when confidence in the rating is not high, there is a tendency to shift from an extreme high or low rating towards a middling rating, thus reducing the maximum possible size of any error. Research using fMRI scanning showed that BOLD response was larger for extreme ratings than for medium ratings. This was the case even when subjects were not specifically required to indicate their level of confidence.
Scanning showed that the ventromedial could encode the rating of pleasantness and confidence in this level of rating at the same time. The ventromedial processing is thus not just a valuation signal, but also contains an estimate of confidence in this valuation. The integration of confidence about a signal is seen as a neural process that happens automatically. This process applies both to measurable external features, such as the brightness of a light, and also to more subjective measures such as pleasantness. The degree of confidence in value ratings is suggested to be likely to effect subsequent choices of behaviour or action by a subject.