No abstract

It has been suggested that contextual fear conditioning can be supported by either an elemental system, where individual features of the environment are associated with shock, or a configural system, where environmental features are bound together and associated with shock. Although the retrosplenial cortex (RSC) is known to be involved in contextual fear conditioning, it is not clear whether it contributes to the elemental or configural system. To isolate the role of the RSC in contextual fear conditioning, the current experiments examined the influence of RSC lesions on the context preexposure facilitation effect, a procedure known to produce conditioning to a configural representation of context. In Experiment 1, rats that were preexposed to the conditioning context froze more compared to rats that were not, replicating the context preexposure facilitation effect. Although pretraining lesions of the RSC had no impact on the context preexposure facilitation effect (Experiment 2a), posttraining lesions attenuated the effect (Experiment 2b), suggesting that the RSC normally contributes to a configural context representation. Retrohippocampal contributions to contextual fear conditioning are discussed. (PsycINFO Database Record

Although the retrosplenial cortex (RSC) is critically involved in spatial learning and memory, it appears to have more selective contributions to learning and memory for discrete cues. For example, damage to the RSC does not impair Pavlovian delay fear conditioning to a discrete auditory cue (e.g., tone), when RSC manipulation occurs just prior to, or shortly after, conditioning. In contrast, when lesions of the RSC occur following a substantial retention interval (e.g., 28 days), the RSC is necessary for retrieval of fear to the tone. Thus, the RSC makes time-dependent contributions to memory retrieval for discrete auditory cues. The purpose of the current experiment was to assess if the time-dependent involvement of the RSC in cue-specific fear memory extended to cues of other sensory modalities. Rats firsts underwent fear conditioning to a visual stimulus, and lesions of the RSC subsequently occurred 1 or 28 days later. Lesions of the RSC impaired fear expression when made 28 days after conditioning, but not when made 1 day following conditioning. Coupled with previous findings, the current results suggest the RSC is necessary for retrieval of remotely acquired cued fear memories across multiple modalities. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Extinction of fear to a Pavlovian conditioned stimulus (CS) is known to be context-specific. When the CS is tested outside the context of extinction, fear returns, or renews. Several studies have demonstrated that renewal depends upon the hippocampus, although there are also studies where renewal was not impacted by hippocampal damage, suggesting that under some conditions context encoding and/or retrieval of extinction depends upon other regions. One candidate region is the retrosplenial cortex (RSC), which is known to contribute to contextual and spatial learning and memory. Using a conditioned-suppression paradigm, Experiment 1 tested the impact of pre-training RSC lesions on renewal of extinguished fear. Consistent with previous studies, lesions of the RSC did not impact acquisition or extinction of conditioned fear to the CS. Further, there was no evidence that RSC lesions impaired renewal, indicating that contextual encoding and/or retrieval of extinction does not depend upon the RSC. In Experiment 2, post-extinction lesions of either the RSC or dorsal hippocampus (DH) also had no impact on renewal. However, in Experiment 3, both RSC and DH lesions did impair performance in an object-in-place procedure, an index of place memory. RSC and DH contributions to extinction and renewal are discussed.

Although the retrosplenial cortex (RSC) is necessary for the retrieval of remotely acquired fear to a discrete auditory cue, it is not necessary for the retrieval of recently acquired cued-fear memories. Thus, the RSC's role in memory retrieval for discrete cues is time-dependent. The purpose of the current experiment was to identify the larger cortical circuit involved in the retrieval of remotely-acquired auditory fear memories. One candidate circuit involves the RSC and secondary auditory cortex; the secondary auditory cortex is also necessary for the retrieval of remotely acquired auditory fear memories (Sacco & Sacchetti, 2010), and sends direct projections to the RSC. To test this possibility, we assessed retrieval of remote memory following functional disconnection of the RSC and secondary auditory cortex. Complete disconnection of these regions produced a larger impairment in fear expression to a remotely acquired auditory cue compared to partial disconnection of these regions. These results are consistent with the notion that RSC and secondary auditory cortex form a functional circuit involved in the retrieval of remotely acquired fear to a discrete auditory cue. (PsycINFO Database Record (c) 2018 APA, all rights reserved).