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The retrosplenial cortex (RSP) and the posterior parietal cortex (PPC) are the primary sources of cortical sensory input to the postrhinal cortex (POR) in rodents. Together, these areas compose a major corticohippocampal circuit that is involved in processing visuospatial information. The POR has been implicated in contextual learning and memory, consistent with the type of information presumably being processed by this region. By comparison, little is known about the role of the RSP or the PPC in contextual learning. In the present study, rats were trained either before or after surgery in a standard signaled fear conditioning task in which an auditory cue was paired with foot shock. Contextual fear and tone-specific fear were assessed in subsequent test sessions. In Experiment 1, electrolytic damage to the RSP either before or immediately after training impaired the expression of contextual fear but not tone-specific fear. In contrast, electrolytic damage to the PPC had no effect on conditional fear to the context or the tone in Experiment 2. These findings indicate that the RSP, but not the PPC, contributes to the processing of contextual information by the POR corticohippocampal processing stream. [ABSTRACT FROM AUTHOR]

The retrosplenial cortex (RSP) is highly interconnected with medial temporal lobe structures, yet relatively little is known about its specific contributions to learning and memory. One possibility is that RSP is involved in forming associations between multiple sensory stimuli. Indeed, damage to RSP disrupts learning about spatial or contextual cues and also impairs learning about co-occurring conditioned stimuli (CSs). Two experiments were conducted to test this notion more rigorously. In Experiment 1, rats were trained in a serial feature negative discrimination task consisting of reinforced presentations of a tone alone and nonreinforced serial presentations of a light followed by the tone. Thus, in contrast to prior studies, this paradigm involved serial presentation of conditioned stimuli (CS), rather than simultaneous presentation. Rats with damage to RSP failed to acquire the discrimination, indicating that RSP is required for forming associations between sensory stimuli regardless of whether they occur serially or simultaneously. In Experiment 2, a sensory preconditioning task was used to determine if RSP was necessary for forming associations between stimuli even in the absence of reinforcement. During the first phase of this procedure, one auditory stimulus was paired with a light while a second auditory stimulus was presented alone. In the next phase of training, the same light was paired with food. During the final phase of the procedure both auditory stimuli were presented alone during a single session. Control, but not RSP-lesioned rats, exhibited more food cup behavior following presentation of the auditory cue that was previously paired with light compared with the unpaired auditory stimulus, indicating that a stimulus-stimulus association was formed during the first phase of training. These results support the idea that RSP has a fundamental role in forming associations between environmental stimuli. [ABSTRACT FROM AUTHOR]

The majority of research regarding contextual learning and memory has focused on the contributions of the hippocampus and related medial temporal lobe structures. However, little is known about other possible cortical contributions to these processes. Our laboratory recently demonstrated that electrolytic lesions of the retrosplenial cortex (RSP), a posterior region of cingulate cortex, impaired contextual but not cue-specific fear conditioning. The present experiments further examined the role of RSP in contextual fear memory using fiber-sparing neurotoxic lesions and both signaled and unsignaled fear conditioning paradigms. Despite comparable acquisition of the conditioned fear response, rats with neurotoxic lesions of RSP exhibited impaired contextual memory relative to control animals in both the signaled and unsignaled paradigms. These results further suggest an important role for RSP in contextual learning and memory. [ABSTRACT FROM AUTHOR]

Lesions of retrosplenial cortex (RSP) disrupt spatial and contextual learning, suggesting that RSP may have a fundamental role in processing overlapping, or simultaneously presented stimuli. If so, then RSP lesions might also be expected to disrupt learning that requires the concurrent processing of phasic conditioned stimuli. In Experiment 1, rats were trained in a compound feature negative discrimination task in which a tone was presented and immediately followed by food on some trials, while on other trials a visual stimulus was simultaneously presented along with the tone and not reinforced. Normal rats learned to discriminate between the trials but RSP-lesioned rats exhibited low levels of conditioning on both types of trials. Experiment 2 demonstrated that this effect was not simply due to a general inability to form associations, since RSP-lesioned rats exhibited normal responding when the visual stimulus was presented alone and paired with food. These findings support the view that RSP has an important role in learning that involves the processing of simultaneously presented stimuli and have implications for understanding the functional relationship between the hippocampus and RSP. [ABSTRACT FROM AUTHOR]

The retrosplenial cortex (RSP) and the posterior parietal cortex (PPC) are the primary sources of cortical sensory input to the postrhinal cortex (POR) in rodents. Together, these areas compose a major corticohippocampal circuit that is involved in processing visuospatial information. The POR has been implicated in contextual learning and memory, consistent with the type of information presumably being processed by this region. By comparison, little is known about the role of the RSP or the PPC in contextual learning. In the present study, rats were trained either before or after surgery in a standard signaled fear conditioning task in which an auditory cue was paired with foot shock. Contextual fear and tone-specific fear were assessed in subsequent test sessions. In Experiment 1, electrolytic damage to the RSP either before or immediately after training impaired the expression of contextual fear but not tone-specific fear. In contrast, electrolytic damage to the PPC had no effect on conditional fear to the context or the tone in Experiment 2. These findings indicate that the RSP, but not the PPC, contributes to the processing of contextual information by the POR corticohippocampal processing stream. [ABSTRACT FROM AUTHOR]

This study assessed basic learning and attention abilities in Wistar-Kyoto hyperactive (WKHA) rats using appetitive conditioning preparations. Two measures of conditioned responding to a visual stimulus, orienting behavior (rearing on the hind legs), and food cup behavior (placing the head inside the recessed food cup) were measured. In Experiment 1, simple conditioning, but not extinction, was impaired in WKHA rats compared with Wistar rats. In Experiment 2, nonreinforced presentations of the visual cue preceded the conditioning sessions. WKHA rats displayed less orienting behavior than Wistar rats but comparable levels of food cup behavior. These data suggest that WKHA rats exhibit specific abnormalities in attentional processing as well as in learning stimulus-reward relationships. [ABSTRACT FROM AUTHOR]