Neural Mechanisms Supporting Differential Fear Conditioning in the Medial Geniculate Nucleus of the Thalamus

Phobias and anxiety related disorders interfere with daily living activities and are characterized by maladaptive fear responses. Differential fear conditioning provides a laboratory model to study these disorders while learning about auditory cues during a training session. The medial geniculate nucleus of the thalamus (MgN) important for auditory learning and is functionally divided into two different regions, the medial division (MGm) and the ventral division (MGv). Traditionally, these divisions are thought to relay aversive auditory information to the amygdala during fear-related associative learning, and the MgN may be necessary to process both safety and danger cues during fear learning. To determine if MgN neural plasticity is required for safety and aversive coding, we used infusions of pharmacological agents and quantitative protein assays to focus on the molecular mechanisms of fear memory formation. We found that differential fear conditioning elicits more plasticity in the MgN than a standard single-tone fear conditioning procedure. Furthermore, we found that protein synthesis in the MgN is required for the acquisition of an auditory differential fear memory. Our results suggest that that a more complex auditory task recruits additional neural circuitry to support a fear memory