A thalamo-prefrontal system for representation in executive response choice.

This study demonstrates the neural system potentially involved in the representation of, and choice between, stimulus classifications in an ambiguous, novel, decision-making task. This difficult choice behaviour is taken as an example of a basic executive processing task. Subjects heard sounds that were consonant-vowel combinations that had been distorted and were required to categorize each stimulus as speech-like or not-speech-like. Cerebral activity was measured with positron emission tomography. A neural system (thalamic and medial prefrontal cortical regions) was demonstrated; there was greater activity involved in assigning the sound to the larger class of not-speech-like sounds than to the more restricted category of speech-like sounds. We interpret this activity as reflecting process and representation in a simple central executive task.