Brain-wide maps of expression during fear learning and recall.

induction during learning labels neuronal ensembles in the hippocampus that encode a specific physical environment, revealing a memory trace. In the cortex and other regions, the extent to which induction during learning reveals specific sensory representations is unknown. Here we generate high-quality brain-wide maps of mRNA expression during auditory fear conditioning and recall in the setting of the home cage. These maps reveal a brain-wide pattern of induction that is remarkably similar among fear conditioning, shock-only, tone-only, and fear recall conditions, casting doubt on the idea that reveals auditory-specific sensory representations. Indeed, novel auditory tones lead to as much gene induction in visual as in auditory cortex, while familiar (nonconditioned) tones do not appreciably induce anywhere in the brain. expression levels do not correlate with physical activity, suggesting that they are not determined by behavioral activity-driven alterations in sensory experience. In the thalamus, is induced more prominently in limbic than in sensory relay nuclei, suggesting that may be most sensitive to emotional state. Thus, our data suggest that expression during simple associative learning labels ensembles activated generally by arousal rather than specifically by a particular sensory cue.