Lesions of the head direction cell system impair direction discrimination.

Previous results suggest that directional information from the head direction cell circuit may inform hippocampal place cell firing when an animal is confronted with visually identical environments. To investigate whether such information might also be essential for spatial behavior, we tested adult, male Lister Hooded rats that had received either bilateral lateral mammillary nuclei (LMN) lesions or sham lesions on a four-way, conditional odor-location discrimination in compartments arranged at 60° to one another. We found that significantly fewer rats in the LMN lesion group were able to learn the task compared to the Sham group. We also found that the extent of the behavioral impairment was highly correlated with the degree of tissue loss in the LMN resulting from the lesion. Animals with LMN lesions were also impaired in a nonmatching-to-sample task in a T maze, and the extent of impairment likewise depended on the extent of the lesion. Performance in the odor-location and T-maze tasks was not affected by tissue loss in the medial mammillary nuclei. Together, these results indicate that the LMN, a key node in the head direction circuit, is critical for solving a spatial task that requires a directional discrimination. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Animal models of working memory: a review of tasks that might be used in screening drug treatments for the memory impairments found in schizophrenia.

The Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) meeting on "Selecting Promising Animal Paradigms" focused on a consideration of valid tasks for drug discovery in non-humans. This consensus review is based on a break-out session with experts from academia and industry which considered tasks that tap working memory in animals. The specific focus of the session was on tasks measuring goal maintenance, memory capacity, and interference control. Of the tasks nominated for goal maintenance, the most developed paradigms were operant delayed-non-matching-to-position tasks, and touch-screen variants of these may hold particular promise. For memory capacity, the task recommended for further development was the span task, although it is recognized that more work on its neural substrates is required. For interference control, versions of the n-back task were felt to resemble the deficits found in schizophrenia, although additional development of these tasks is also required.