Friday, November 11, 2011

Where in the brain does 'negative surprise' happen?

Egner points to an article by Alexander and Brown that provides an integrated model of how the brain deals with the non-occurrence of an expected event, such as George Bush and the famous non-opening Chinese door, suggesting this type of negative surprise drives neural responses in the dorsal anterior cingulate cortex and adjacent medial prefrontal cortex (dACC/mPFC), regions whose functions have been disputed in recent years. Their model provides a common denominator for a wide range of dACC/mPFC responses that have previously been attributed to diverse cognitive computations, making it a promising candidate for an integrative theory of this region's function. Their predicted response–outcome (PRO) model attempts to reconcile diverse finding, by suggesting that individual neurons generate signals reflecting a learned prediction of the probability and timing of the various possible outcomes of an action. These prediction signals are inhibited when the corresponding predicted outcome actually occurs. The resulting activity is therefore maximal when an expected outcome fails to occur, which suggests that what mPFC signals, in part, is the unexpected non-occurrence of a predicted outcome. Here is their abstract:
The medial prefrontal cortex (mPFC) and especially anterior cingulate cortex is central to higher cognitive function and many clinical disorders, yet its basic function remains in dispute. Various competing theories of mPFC have treated effects of errors, conflict, error likelihood, volatility and reward, using findings from neuroimaging and neurophysiology in humans and monkeys. No single theory has been able to reconcile and account for the variety of findings. Here we show that a simple model based on standard learning rules can simulate and unify an unprecedented range of known effects in mPFC. The model reinterprets many known effects and suggests a new view of mPFC, as a region concerned with learning and predicting the likely outcomes of actions, whether good or bad. Cognitive control at the neural level is then seen as a result of evaluating the probable and actual outcomes of one's actions.

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