While all groups are affected by the COVID-19 pandemic, the elderly, underrepresented minorities, and those with underlying medical conditions are at the greatest risk. The high rate of consumption of diets high in saturated fats, sugars, and refined carbohydrates (collectively called Western diet, WD) worldwide, contribute to the prevalence of obesity and type II

It is argued that the hippocampus contributes to contextual fear conditioning by supporting the acquisition of a conjunctive memory representation of context, which associates with shock. This function was examined by studying the context pre-exposure facilitation effect (CPFE). A rat that is shocked immediately after being placed into a context subsequently displays almost no fear of that context. However, if it is pre-exposed to the context the day before immediate shock, it displays significant freezing to that context. By using 5-aminomethyl-3-hydroxysoxazole to temporarily inactivate the dorsal hippocampus (DH) at three different phases of the procedure, which produces the CPFE, we show that the hippocampus is necessary for the following: (1) acquisition of the context memory, (2) retrieval of this memory at the time of immediate shock, and (3) retrieval of the context-shock memory at the time of testing. In contrast, inactivating the DH before a standard contextual shock experience had no effect on contextual fear conditioning. These results support the view that two processes can support contextual fear conditioning: (1) conditioning to the conjunctive representation, which depends on the hippocampus, and (2) conditioning to the features that make up the context, which does not.

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It has been proposed that contextual fear conditioning depends on 2 processes: (a) construction of a conjunctive representation of the features that make up the context and (b) association of the representation with shock. Support for this view comes from studies indicating that prior exposure to the conditioning context facilitates contextual fear conditioning supported by immediate shock. Thus, conditioning produced by immediate shock is to the memory representation of the preexposed context, which is activated by retrieval cues associated with this context. The authors' experiments support this interpretation and indicate that this process depends on an intact hippocampal formation. These results support the hypothesis that the hippocampal formation supports contextual fear conditioning by storing a conjunctive representation of context.The importance of fear conditioning to the neurobiology of memory emerged when it was reported that fear to the context or place in which shock occurred (contextual fear) and fear to a discrete auditory cue paired with the shock were differentially dependent upon the hippocampal formation (Kim & Fanselow, 1992;Phillips & LeDoux, 1992;Selden, Everitt, Jarrard, & Robbins, 1991). Damage to the hippocampal formation impaired contextual but not auditory-cue fear conditioning. The selectivity of the result suggested that the study of contextual fear conditioning would provide a valuable method for studying the mechanisms by which the hippocampus contributes to memory and is now commonly used for this purpose.Several theorists have argued that contextual fear conditioning depends on two independent learning processes: The rat (a) constructs and stores a conjunctive representation of the independent features of the context and (b) associates that representation with shock (see Fanselow & Rudy, 1998;Rudy, 1996;Rudy & Morledge, 1994;Young, Bohenek, & Fanselow, 1994). In this framework, it is the acquisition of the conjunctive representation that requires the hippocampus. The associative process does not.There is considerable support for the view that rats can acquire a representation of context, independent of associating it with shock. This support comes from a range of experiments that have demonstrated what we call the context preexposure facilitation effect-the fact that preexposure to the conditioning context the day before a context-shock experience can enhance the low levels of fear contextual conditioning that otherwise would occur