Event Title

The Effects of Permanent Damage to the Retrosplenial Cortex on Contextual Learning in Rats

Location

Science Center, Bent Corridor

Start Date

9-26-2014 12:00 PM

End Date

9-26-2014 1:20 PM

Poster Number

32

Abstract

Many studies have provided evidence supporting the importance of the hippocampus for contextual and spatial learning and memory. More specifically, studies have identified the retrosplenial cortex (RSC) as a major contributor to the hippocampal ‘where’ pathway, a neural circuit that provides physical and temporal details about an environment to the hippocampus. Recent literature suggests that the RSC plays a role in the acquisition/retention of stimulus-stimulus memories, but that damage to that region interrupts these processes. The present experiment was designed to provide evidence supporting that the RSC is necessary for stimulus-stimulus learning. In this experiment, rats received either a permanent electrolytic RSC lesion or a sham surgery and were presented with an aversive learning and memory paradigm. In phase one of the test, rats were placed in two contexts that were made distinct by the olfactory and visual stimuli present in each context; one exposure occurred in the morning and the other in the afternoon. Context A consisted of a chamber decorated with stripes and scented with peppermint, while context B consisted of a chamber decorated with a dotted background and scented with orange. Auditory cues were presented at regular intervals in each context; a tensecond white noise was heard in Context A and a ten-second Tone was heard in Context B. The first phase lasted four days and was designed to induce stimulus-stimulus learning. During phase two, rats were fear conditioned in Context C; the previous white noise that was heard in Context A was coupled with an aversive 0.5mA shock while the Tone that was heard in Context B was not. In phase three, contextual fear memory was assessed by observing freezing behavior upon re-exposure to contexts A and B. In phase four auditory fear memory was assessed by observing freezing behavior during auditory cue presentations that occurred in Context C coupled with auditory stimuli only. Phase three was designed to assess the rats’ ability to associate the aversive shock with context A, and so it is predicted that rats that received permanent RSC lesions would freeze less in context A or equally between the contexts, showing that they failed to discriminate between the aversive shock and neutral white noise. In contrast, rats with sham lesions were predicted to learn the associations and exhibit increased freezing behavior in context A compared to their response in context B.

Award

Jessica Hubert, Oberlin College Research Fellow (OCRF)

Project Mentor(s)

Siobhan Robinson, Neuroscience

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Sep 26th, 12:00 PM Sep 26th, 1:20 PM

The Effects of Permanent Damage to the Retrosplenial Cortex on Contextual Learning in Rats

Science Center, Bent Corridor

Many studies have provided evidence supporting the importance of the hippocampus for contextual and spatial learning and memory. More specifically, studies have identified the retrosplenial cortex (RSC) as a major contributor to the hippocampal ‘where’ pathway, a neural circuit that provides physical and temporal details about an environment to the hippocampus. Recent literature suggests that the RSC plays a role in the acquisition/retention of stimulus-stimulus memories, but that damage to that region interrupts these processes. The present experiment was designed to provide evidence supporting that the RSC is necessary for stimulus-stimulus learning. In this experiment, rats received either a permanent electrolytic RSC lesion or a sham surgery and were presented with an aversive learning and memory paradigm. In phase one of the test, rats were placed in two contexts that were made distinct by the olfactory and visual stimuli present in each context; one exposure occurred in the morning and the other in the afternoon. Context A consisted of a chamber decorated with stripes and scented with peppermint, while context B consisted of a chamber decorated with a dotted background and scented with orange. Auditory cues were presented at regular intervals in each context; a tensecond white noise was heard in Context A and a ten-second Tone was heard in Context B. The first phase lasted four days and was designed to induce stimulus-stimulus learning. During phase two, rats were fear conditioned in Context C; the previous white noise that was heard in Context A was coupled with an aversive 0.5mA shock while the Tone that was heard in Context B was not. In phase three, contextual fear memory was assessed by observing freezing behavior upon re-exposure to contexts A and B. In phase four auditory fear memory was assessed by observing freezing behavior during auditory cue presentations that occurred in Context C coupled with auditory stimuli only. Phase three was designed to assess the rats’ ability to associate the aversive shock with context A, and so it is predicted that rats that received permanent RSC lesions would freeze less in context A or equally between the contexts, showing that they failed to discriminate between the aversive shock and neutral white noise. In contrast, rats with sham lesions were predicted to learn the associations and exhibit increased freezing behavior in context A compared to their response in context B.