Impaired Retrieval of Spatial Memory and Response Perseveration in a Radial Arm Maze After Muscimol Inactivation of the Anterodorsal Thalamus.

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Presentation Date


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Society for Neuroscience

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San Diego, CA


The ability to navigate depends on neural systems involved in tracking an animal’s moment-to-moment changes in directional orientation and spatial location when moving from place to another. Previous studies have shown that the anterodorsal thalamus (AD) contains a large population of head direction cells, which fire as a function of an animal’s directional orientation in an environment, thereby providing a neuron-like compass guiding navigation. Recent work has demonstrated that when the AD is damaged animals display poor performance on spatial reference/working memory tasks. However, while studies have confirmed that AD lesions impair the acquisition of new spatial information, few have attempted to dissociate the unique contributions of the AD to the acquisition vs. retrieval of allocentric spatial information. Here, we trained rats in a radial arm maze (RAM) procedure that requires the acquisition of directional trajectories to obtain a reward. Animals were trained to asymptotic levels (mean = 67.9% correct + 3.2% SEM; chance performance = 25%). Twenty-four hours after training, animals were administered muscimol inactivation of the AD before a 4 trial probe test. Specific measures across training and probe testing included: latency to complete the task, amount of errors (working and reference memory), and percent of correct arm choices per trial. We found that when the AD was inactivated, RAM latency and reference memory were significantly higher, and the percent correct was significantly lower than control animals. In addition, a large number of working memory and perseverative errors were observed in AD inactivated animals throughout testing, suggesting a general absence of improved navigation across training trials. In contrast to retrieval and working memory deficits, it was observed that inactivated animals could express a non-spatial “cued” behavior, indicating that the impairments were specific to spatial processing. Taken together, the results above suggest that the AD modulates the retrieval of previously acquired allocentric spatial information in a RAM procedure, but also suggests a critical role in the online guidance of accurate spatial behavior. The results are discussed in relation to the anterodorsal thalamo-cortical circuits involved in spatial information processing.



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