Functional Interaction between the Hippocampus and Nucleus Accumbens Shell Is Necessary for the Acquisition of Appetitive Spatial Context Conditioning

Abstract

The nucleus accumbens (NAc) has been implicated in a variety of associative processes that are dependent on the integrity of the amygdala and hippocampus (HPC). However, the extent to which the two subregions of the NAc, the core and shell, form differentiated circuits within the amygdala-and hippocampal-ventral striatal circuitry remains unclear. The present study investigated the effects of selective excitotoxic lesions of the nucleus accumbens shell or core subregion on appetitive elemental cue and context conditioning, shown previously to be dependent on the basolateral amygdala and hippocampus, respectively. Rats were trained sequentially to acquire discrete conditioned stimulus-sucrose conditioning, followed by spatial context-sucrose conditioning in a place preference apparatus characterized by three topographically identical chambers, the chambers being discriminable only on the basis of path integration. NAc shell lesions selectively impaired the acquisition of conditioned place preference and the use of spatial information to retrieve information about a discrete cue, whereas, as expected, NAc core lesions attenuated the acquisition of cue conditioning compared with sham rats. In a subsequent experiment, disconnection of the HPC from the NAc shell using unilateral asymmetric lesions of each structure resulted in a pattern of impairment in place conditioning and context-dependent cue retrieval similar to that produced by NAc shell lesions. These data not only suggest that the NAc core and shell subregions subserve distinct associative processes but also that the NAc shell and HPC are important functional components of a limbic corticostriatal network involved in spatial context conditioning.

Lateralized human hippocampal activity predicts navigation based on sequence or place memory

“…Dorsal striatal activations (centered on the caudate) suggest that simpler S-R associations form part of both of the more cognitive strategies (allocentric and sequential egocentric), consistent with a striatal role in learning skilled responses and with an interaction between hippocampus and striatum in route recognition (27). The ventral striatal activation observed in probe trials and training trials is consistent with suggestions that this area acts in concert with the hippocampus in spatial memory consolidation and learning (28). The medial prefrontal activation seen in training, egocentric, and allocentric trials is consistent with its role as a coordinator between striatal and hippocampal systems, as suggested by studies in rodents (29) and humans (16).…”

A GABAergic Projection from the Centromedial Nuclei of the Amygdala to Ventromedial Prefrontal Cortex Modulates Reward Behavior

“…That is, although both exploring and nose poking are motivationally required actions to receive a reward, operant nose poking for a reward has more complex stages to be achieved because it requires relatively unnatural behavior compared with traveling in a testing box. This complexity makes failing to form nose-poking self-stimulation more difficult to interpret (Ito et al, 2005;Ito et al, 2008;Malkki et al, 2010). In fact, whereas there was a significant preference effect associated with , and recall (day 10).…”

Theta Phase Precession in Rat Ventral Striatum Links Place and Reward Information

“…In general, the hippocampus-ventral striatal projection has long been implicated in the modulation of motivated behavior (Mogenson et al, 1980;Pennartz et al, 1994;Bast and Feldon, 2003;. In particular, a recent study disconnecting the hippocampus and ventral striatum (nucleus accumbens shell) found impairments in a conditioned place preference task, suggesting that this projection supports the learning of place-reward associations (Ito et al, 2008).…”