The focus of our research in systems neurobiology is to understand how the brain processes information from past and present and how this information is used for making complex decisions. Researchers at the Institute have developed experiments using rats running in mazes in order to learn about the brain regions involved in these activities. Three brain regions are involved: the hippocampus, parietal cortex, and the prefrontal cortex. These brain regions integrate the same type of information, but in very different ways. The hippocampus registers the past and current positions of the animal. The parietal cortex records the animal’s presence in particular parts of a path, no matter the animal’s position in the room. The prefrontal cortex combines multiple types of information about the animal’s actions and position with the animal’s expectation of reward. This region is regarded as an “associative” area because it receives convergent input from many other regions of the brain. Distinct patterns of activity can be seen in the prefrontal neurons depending on the size of the reward and how sure the animal is about the potential of receiving the reward.

While some regions within the hippocampus, such as CA1, have been extensively studied, much less is known about the regions such as the dentate gyrus. Using mazes which included prominent sensory cues, a reward was given only if the rat was able to navigate along a path specified by those cues. The results showed that the activity of neurons in the dentate gyrus peaked at maze sites bearing cues and at maze sites where one or another path had to be chosen. Thus, the dentate gyrus functions to link cues demanding particular choices with the actual implementation of those choices.

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