Contextual fear learning in virtual reality: The role of the vmPFC and the hippocampus in the contextual modulation of fear expression

Keywords
No Thumbnail Available
Issue Date
2015-08-13
Language
en
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Correctly using contextual information to modulate our assessment of a situation is crucial for healthy emotion and cognition, and deficits in this ability to correctly contextualise information may lead to psychopathology such as post-traumatic stress disorder (PTSD). Using a virtual reality (VR) model for delay differential contextual fear conditioning combined with functional magnetic resonance imaging (fMRI), we aimed to shed some light on how the brain enables this contextual modulation of fear. Inside the VR, two different buildings represented a safe context and a threat context, respectively. Two different cues (CS+ and CS-) were presented in both buildings in exactly the same way, but the CS+ was consistently (at a reinforcement rate of 100%) paired with a mild electric shock only in the threat context and never in the safe context, while the CS- was never paired with a shock. In order to validate the presence of conditioned fear in the threat context, but not the safe context, we used skin conductance responses (SCR) and pupil dilation, which indeed confirmed that conditioned fear in response to the CS+ (as compared to the CS-) was present in the threat context, but not the safe context. We observed significantly greater blood-oxygen-level dependent (BOLD) responses for CS+threat>CS-threat than for CS+safe>CSsafe in the dorsal anterior cingulate cortex (dACC), anterior insula, amygdala, hippocampus as well as several other regions, showing that conditioned fear in response to the CS+ was indeed present in the threat context, but not in the safe context. Furthermore, we found a significant cue by context interaction in the ventromedial prefrontal cortex (vmPFC), with significantly greater activity in response to the CS+ in the safe context than in the threat context. This finding is similar to findings of studies on fear extinction, suggesting that change of context and fear extinction are enabled by similar mechanisms linked to the vmPFC. One possibility for such a mechanism is that the vmPFC, in interaction with the hippocampus, inhibits fear expression by signalling safety to other areas implicated in conditioned fear, such as the amygdala and dACC.
Description
Citation
Faculty
Faculteit der Sociale Wetenschappen