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In contrast to the wealth of data describing the neural mechanisms underlying classical conditioning, we know remarkably little about the mechanisms involved in acquisition of explicit contingency awareness. Subjects variably acquire contingency awareness in classical conditioning paradigms, in which they are able to describe the temporal relationship between a conditioned cue and its outcome. Previous studies have implicated the hippocampus and prefrontal cortex in the acquisition of explicit knowledge, although their specific roles remain unclear. We used functional magnetic resonance imaging to track the trial-by-trial acquisition of explicit knowledge in a concurrent trace and delay conditioning paradigm. We show that activity in bilateral middle frontal gyrus and parahippocampal gyrus correlates with the accuracy of explicit contingency awareness on each trial. In contrast, amygdala activation correlates with conditioned responses indexed by skin conductance responses (SCRs). These results demonstrate that brain regions known to be involved in other aspects of learning and memory also play a specific role, reflecting on each trial the acquisition and representation of contingency awareness.

Original publication




Journal article



Publication Date





1007 - 1012


MC216-76 Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.


Hippocampus, Frontal Lobe, Prefrontal Cortex, Humans, Magnetic Resonance Imaging, Awareness, Avoidance Learning, Conditioning, Classical, Memory, Short-Term, Reinforcement (Psychology), Galvanic Skin Response, Adult, Female, Male