Rapid amygdala responses during trace fear conditioning without awareness.

People can learn to associate a face with a later shock even when they are unaware of seeing the face, challenging the view that conscious awareness is necessary for trace fear conditioning. Using magnetoencephalography (MEG) to record amygdala activity, the authors observed rapid neural responses (around 170-200 milliseconds) during the interval between the unperceived face and the shock. These results suggest that unperceived faces can serve as signals for impending threat and that automatic amygdala activation contributes to this learning. The study also describes a novel MEG methodology for investigating subcortical structures.

Study at a glance

Abstract

The role of consciousness in learning has been debated for nearly 50 years. Recent studies suggest that conscious awareness is needed to bridge the gap when learning about two events that are separated in time, as is true for trace fear conditioning. This has been repeatedly shown and seems to apply to other forms of classical conditioning as well. In contrast to these findings, we show that individuals can learn to associate a face with the later occurrence of a shock, even if they are unable to perceive the face. We used a novel application of magnetoencephalography (MEG) to non-invasively record neural activity from the amygdala, which is known to be important for fear learning. We demonstrate rapid (∼ 170-200 ms) amygdala responses during the stimulus free period between the face and the shock. These results suggest that unperceived faces can serve as signals for impending threat, and that rapid, automatic activation of the amygdala contributes to this process. In addition, we describe a methodology that can be applied in the future to study neural activity with MEG in other subcortical structures.