Cooperation & Competition Between Navigation Systems in the Rat Brain: The Role of the Hippocampus and Striatum During a Dissociative Maze Task

While many tend to think of memory systems in the brain as a single process, in reality several experiments have supported multiple dissociations of different forms of learning, such as spatial learning and response learning. In both humans and rats, the hippocampus has long been shown to be specialized in the storage of spatial and contextual memory whereas the striatum is associated with motor responses and habitual behaviors. Previous studies have examined how damage to hippocampus or striatum has affected the acquisition of either a spatial or response navigation task. However even in a very familiar environment organisms must continuously switch between place and response strategies depending upon circumstances. The current research investigates how these two brain systems interact under normal conditions to produce navigational behavior. Rats were tested using a task developed by Jacobson and colleagues (2006) in which the two types of navigation could be controlled and studied simultaneously. Rats were trained to solve a plus maze using both a spatial and a response strategy. A cue (flashing light) was employed to indicate the correct strategy on a given trial. When no light was present, the animals were rewarded for making a 90º right turn (motor response). When the light was on, the animals were rewarded for going to a specific goal location (place strategy). After learning the task, animals had a sham surgery or dorsal striatum or hippocampus damaged. In order to investigate the individual role of each brain system and evaluate whether these brain regions compete or cooperate for control over strategy, we utilized a within-animal comparisons. The configuration of the maze allowed for the comparison of behavior in individual animals before and after specific brain areas were damaged. Animals with hippocampal lesions showed selective deficits on place trials after surgery and learned the reversal of the motor response more rapidly than striatal lesioned or sham rats. Unlike previous findings regarding maze learning, animals with striatal lesions showed deficits in both place and response trials and had difficulty learning the reversal of motor response. Therefore, the effects of lesions on the ability to switch back and forth between strategies were more complex than previously suggested. This work may reveal important new insight on the integration of hippocampal and striatal learning systems, and facilitate a better understanding of the brain dynamics underlying similar navigational processes in humans.

Conversations between Anthropologists and Economists

Interdisciplinary citation patterns and other indicators of the flow and sharing of academic knowledge suggest that economists and anthropologists do not talk to each other. Previous studies of this puzzling trend have typically attributed the problem to methodological differences between the two disciplines. Although there are significant differences between economics and anthropology in behavioral assumptions and modes of inquiry, similar differences exist between them and other disciplines (some with much heavier volumes of cross-citations with economics or anthropology), suggesting that the source of the problem lies elsewhere. This paper considers the problem at a deeper level by examining systematic differences in the preferences, capabilities, and literary cultures of economists and anthropologists. Adopting a rhetorical perspective, I consider not the firms, households, or tribes as the principal objective of analysis in the two disciplines, but the conversations between these units. These conversations (through non-verbal as well as verbal media) can be grouped into two genres, based on the type of problem they aim to solve. Those in the first genre aim to solve the problem of interest--how to align the incentives of the parties involved. Those in the second genre deal with the problem of knowledge--how to align localized, and dispersed information. Economists are interested and capable of dealing with primarily, if not exclusively, the first genre, and anthropologists focus on the second. This difference has far reaching consequences for how economists and anthropologists conduct their own scholarly conversations with their own colleagues, why they are having difficulty talking to each other across disciplinary boundaries, and what can be done to change the patterns of communication.