Recent research has shown that the brain encodes geographic information as a function of a given landmark’s distance to enticing rewards. For example, a log in a forest would be pinned on a squirrel’s mental map in relation to how close by the squirrel found some nuts.
How the different signals of place (log) and reward (nuts) were encoded in the brain was not fully understood. Edward Han, PhD, an assistant professor of neuroscience at WashU Medicine, working with graduate student Zahra Dhanerawala, have shown in mice that the two functions appear to be controlled by different groups of cells in the hippocampus, a structure deep within the brain that handles most memory functions.
The finding was published in Current Biology.
Han and his team used high-resolution imaging to observe the activity of individual brain cells in mice as they tried to find food rewards in a virtual reality environment. The researchers observed that a specific type of interneuron — a class of cell that controls information flow between neurons — was activated around neurons that fired in response to finding the reward, strengthening their signals. When the scientists turned down activity in those interneurons, the mice were unable to retain the memory of where they had previously received rewards, even while they were still able to navigate the virtual environment. When they turned up activity in the interneurons beyond normal levels, the mice performed even better on the task.
The finding that place and reward maps are encoded in different brain circuits suggests that it may be possible to treat learning and cognitive disorders — including those that damage the hippocampus such as Alzheimer’s disease — by targeting interneurons that contribute to specific memory functions.
Read more about the finding on the Department of Neuroscience website.