MIT Study: Brain Circuit in Anterior Thalamus is Critical for Memory
A study published this week in ScienceDaily sheds light on the underlying mechanisms of memory formation and decline. As described in the story, researchers at the Massachusetts Institute of Technology (MIT) have found a brain circuit in the anterior thalamus that is critical for memory function.
The research was funded by the Stanley Center for Psychiatric Research at the Broad Institute, the Hock E. Tan and K. Lisa Yang Center for Autism Research at MIT, as well as by the James and Patricia Poitras Center for Psychiatric Disorders Research at MIT.
Guoping Feng, the James W. and Patricia T. Poitras Professor in Brain and Cognitive Sciences at MIT, a member of the Broad Institute of Harvard and MIT, and the associate director of the McGovern Institute for Brain Research at MIT, commented on the findings. Feng is also an author of the study.
"By understanding how the thalamus controls cortical output, hopefully we could find more specific and druggable targets in this area, instead of generally modulating the prefrontal cortex, which has many different functions," he said.
The discovery was made during an experiment with mouse models, where researchers were hoping to examine the anteroventral thalamus closely to determine the structure’s role in spatial working memory tasks.
The mice were trained to run through a T-shaped, simple maze. The maze, with one arm of the T blocked off, was identified as the first part of the experiment. Here, mice were forced to use the only remaining arm of the T to complete the maze. In the second phase of the experiment, mice are waiting for the second maze run. In the third phase, the second run begins, and mice are evaluated based on whether they chose an arm based upon the previously blocked arm of the T.
While the mice experienced these three experimental phases, the researchers used optogenetics to manipulate neural activity in the anterodorsal and anteroventral thalamus regions. Optogenetics describes a way to use light control to turn cells off or on. Using this technique, neurons in the thalamus could be inhibited. The experiment results show that when anteroventral thalamus activity during phase two, when the mice are waiting for the second run, the mice performed poorly. The anteroventral thalamus, specifically, aids in contextual learning.
After making the connection between memory-related tasks and the anteroventral thalamus, the research moved on to older, 14-month-old mice. In these mice, stimulation of the anteroventral neurons enhanced their performance on the three-phase T-shaped maze test.
The importance of this finding is supported by data showing that adults experience a decline in anterior thalamus activity as they age. As a result, spatial memory-related tasks become more difficult and memories are retained less. The thalamus is critical for mental maps of physical places, memory formation and memory organization.
This discovery could be used in conjunction with the development of technology to stimulate neural activity. Using such technology, age-related memory decline could be prevented. Further research will be conducted at MIT to determine what cells might be the best targets for a technology.