The dorsal hippocampus is essential for context discrimination but not for contextual conditioning.

Abstract

The authors describe how (a) the timing of hippocampal lesions and (b) the behavioral-representational demands of the task affect the requirement for the hippocampus in contextual fear conditioning. Post- but not pretraining lesions of the hippocampus greatly reduced contextual fear conditioning. In contrast, pretraining lesions of the hippocampus abolished context discrimination, a procedure in which mice are trained to discriminate between 2 similar chambers (shock context vs. no-shock context). Whereas either contextual- or cue-based strategies can be used to recognize an aversive context, discrimination between similar contexts is optimally acquired by contextual (hippocampal)-based strategies. In keeping with the lesion results, Nf1(+/-)/Nmdar1(+/-) mutant mice, which have spatial learning deficits, are impaired in context discrimination but not in contextual conditioning. Together, these data dissociate hippocampal and nonhippocampal contributions to contextual conditioning, and they provide direct evidence that the hippocampus plays an essential role in the processing of contextual stimuli.

The aging hippocampus: A multi-level analysis in the rat

“…The literature indicates that neurotoxic damage to dorsal hippocampus before conditioning has little or no effect on the acquisition of contextual fear conditioning (Cho et al, 1999;Frankland et al, 1998;Maren et al, 1997;Richmond et al, 1999) but damage to the hippocampus following learning produces severe retrograde amnesia (Anagnostaras et al, 1999;Maren et al, 1997). This dissociation between anterograde and retrograde effects clearly parallels our current conclusions about elemental visual discriminations.…”

Scopolamine and Pavlovian Fear Conditioning in Rats Dose-Effect Analysis

“…whereas tone conditioning requires the sampling of only one cue (e.g., Rudy 1996;Anagnostaras et al 1995). This is still somewhat similar to the role we have proposed for the hippocampus in contextual fear conditioning, which we have argued forms the contextual CS by assembling multiple cues into a single spatial or configural representation Young et al 1994;Maren et al 1998;Frankland et al 1998;Anagnostaras et al 1999). Nonetheless, ruling out the less exciting possibility that scopolamine produced deficits through purely sensory disturbance will require further investigation.…”

Models and mechanisms of anxiety: evidence from startle studies

“…Not all studies find that lesions of the hippocampus affect context conditioning (Frankland et al 1998;McNish et al 1997;Winocur 1997). Recent preclinical evidence indicates that context conditioning is hippocampus-dependent for complex but not simple environments (Moses et al 2007).…”