Abstract
Projections from auditory cortex to the amygdala are thought to contribute to the induction of auditory fear learning. In addition, fear conditioning has been found to enhance cortical responses to conditioned tones, suggesting that cortical plasticity contributes to fear learning. However, the functional role of auditory cortex in the retrieval of fear memories is unclear and how fear learning regulates cortical sensory representations is not well understood. To address these questions, we use acute optogenetic silencing and chronic two-photon calcium imaging in mouse auditory cortex during fear learning. Longitudinal imaging of neuronal ensemble activity reveals that discriminative fear learning modulates cortical sensory representations via the suppression of cortical habituation.
Highlights
While the amygdala plays a critical role in associative fear conditioning, neural circuits in sensory cortex are thought to contribute to the acquisition and expression of learned fear (LeDoux, 2000; Maren and Quirk, 2004; Herry and Johansen, 2014)
Since cortical inactivation in the absence of tone presentation had no effect on lick rate (n = 4 mice, paired t-test, p = 0.512), these results indicate that auditory cortex is necessary for memory retrieval after discriminative fear learning
We found that the auditory cortex is necessary for discrimination of CS+ and CS− tones during memory retrieval and that fear conditioning regulates the discriminability of cortical sensory representations
Summary
While the amygdala plays a critical role in associative fear conditioning, neural circuits in sensory cortex are thought to contribute to the acquisition and expression of learned fear (LeDoux, 2000; Maren and Quirk, 2004; Herry and Johansen, 2014). Electrophysiological studies have reported that neurons in auditory cortex show enhanced responses to conditioned tones immediately after fear conditioning (Weinberger and Diamond, 1987; Quirk et al, 1997; Weinberger, 2004, 2015), leading to the proposal that changes in cortical sensory representations contribute to memory strength or stimulus discrimination. These findings are typically based on the responses of small subsets of recorded neurons that appear to show learning-related changes in activity. The inability to record from identified populations of cortical neurons over long time periods has made it difficult to determine how sensory representations are modified to support retrieval of fear memories
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