In favor of general probability distributions: lateral prefrontal and insular cortices respond to stimulus inherent, but irrelevant differences
A key aspect of optimal behavior is the ability to predict what will come next. To achieve this, we must have a fairly good idea of the probability of occurrence of possible outcomes. This is based both on prior knowledge about a particular or similar situation and on immediately relevant new information. One question that arises is: when considering converging prior probability and external evidence, is the most probable outcome selected or does the brain represent degrees of uncertainty, even highly improbable ones? Using functional magnetic resonance imaging, the current study explored these possibilities by contrasting words that differ in their probability of occurrence, namely, unbalanced ambiguous words and unambiguous words. Unbalanced ambiguous words have a strong frequency-based bias towards one meaning, while unambiguous words have only one meaning. The current results reveal larger activation in lateral prefrontal and insular cortices in response to dominant ambiguous compared to unambiguous words even when prior and contextual information biases one interpretation only. These results suggest a probability distribution, whereby all outcomes and their associated probabilities of occurrence—even if very low—are represented and maintained.
KeywordsAmbiguity Uncertainty Probability distributions Prefrontal cortex Anterior insula fMRI
This work was supported by a Beatriu de Pinós postdoctoral grant from the Government of Catalonia (Generalitat de Catalunya) to AMM. We thank T. Gunter for his help with the stimulus material.
- Christoff K, Gabrieli JD (2000) The frontopolar cortex and human cognition: evidence for a rostrocaudal hierarchical organization within the human prefrontal cortex. Psychobiology 28:168–186Google Scholar
- Petrides M (2005b) The rostral-caudal axis of cognitive control within the lateral frontal cortex. In: Dehaene S, Duhamel GR, Hauser GR, Rizzolatti G (eds) From monkey brain to human brain. MIT Press, Cambridge, pp 293–314Google Scholar
- Wagner S (2003) Verbales Arbeitsgedächtnis und die Verarbeitung ambiger Wörter in Wort- und Satzkontexten. Dissertation, Max Planck Institute of Cognitive NeuroscienceGoogle Scholar