In the brain, timing is everything

In the brain, timing is everything
Our brains like to play connect the dots with our memories. If you once heard the angry growl of a dog that was followed by a bite, you might anticipate a painful bite the next time your hear a dog growl. This shows that our brains can link sequential memories, a useful skill when it comes to staying away from harm. Scientists at MIT have identified how two different brain circuits help provide these links. In a new study published in Science, the researchers used optogenetics to show how two different regions of the brain (the hippocampus and an adjacent region known as the entorhinal cortex) interact. The researchers identified a group of excitatory neurons termed "island cells" that are part of layer 2 of the entorhinal cortex. These island cells stimulate inhibitory neurons in the CA1 region of the hippocampus, which interacts with a previously discovered monosynaptic circuit. This interaction keeps the memory of, say, a dog growl, alive long enough to be linked with the memory of the bite. Understanding how these two circuits interact will help us understand how our brains try to balance becoming paralyzed with fear and becoming overly careless, and what happens when this balance is disrupted, such as in PTSD.

Source:
http://web.mit.edu/newsoffice/2014/in-the-brain-timing-is-everything-0123.html
Journal article: Island Cells Control Temporal Association Memory. Science, 2014. DOI: 10.1126/science.1244634
Story via Neuroscience Research Techniques 
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