New research from scientists at the Howard Hughes Medical Institute’s Janelia Research Campus shows that distant parts of the brain are called into action to store a single memory. The brain’s cortex which is the outer layer of tissue thought to be responsible for generating most thoughts and actions relies on connections with a small region in the center of the brain called the thalamus.
The thalamus is best known as a relay center that passes incoming sensory information to other parts of the brain for processing. But clinical discoveries indicate that certain areas of the thalamus may also play a vital part in consciousness and cognitive function. When a memory is formed in the brain, activity in the cells that store the information changes for the duration of the memory. Since individual neurons cannot remain active for more than a few milliseconds on their own, groups of cells work together to store the information. Neurons signaling back and forth can sustain one another’s activity for the seconds that it takes to store a short-term memory.
Svoboda and his colleagues wanted to understand if ALM stores these memories by itself, or if other parts of the brain work in concert with the ALM to store memories. ALM connects to several other brain regions via long-range connections. Zengcai Guo and Hidehiko Inagaki, postdoctoral researchers in Svoboda’s lab, tested those connections one by one, evaluating whether switching off neurons in various brain regions interfered with memory-associated activity in the ALM and impacted animals’ ability to remember their cues.
In further experiments, the team discovered that information flows both ways between the thalamus and the ALM portion of the cortex. The back and forth movement maintains these activity patterns that correspond to the memory. The finding highlights the functional importance of connections between distant parts of the brain, which are often neglected as neuroscientists focus their attention on activity within specific areas.