Pattern separation and tuning shift in human sensory cortex underlie fear memory

Animal research has recognized the role of the sensory cortex in fear memory and two key underlying mechanisms--pattern separation and tuning shift. We interrogated these mechanisms in the human sensory cortex in an olfactory differential conditioning study with a delayed (9-day) retention test. Combining affective appraisal and olfactory psychophysics with functional magnetic resonance imaging (fMRI) multivoxel pattern analysis and voxel-based tuning analysis over a linear odor-morphing continuum, we confirmed affective and perceptual learning and memory and demonstrated associative plasticity in the human olfactory (piriform) cortex. Specifically, the piriform cortex exhibited immediate and lasting enhancement in pattern separation (between the conditioned stimuli/CS and neighboring non-CS) and late-onset yet lasting tuning shift towards the CS, especially in anxious individuals. These findings highlight an evolutionarily conserved sensory cortical system of fear memory, which can underpin sensory encoding of fear/threat and confer a sensory mechanism to the neuropathophysiology of anxiety.