Scientific American Mind Article

In the Scientific American Mind Article “Brain Pathway May Underlie Depression,” JR Minkel investigates the mystery behind the marker for depression. A neuroengineer and psychiatrist named Karl Deisseroth hypothesizes that the electrical chatter in the dentate gyrus contracts in depressed rats. The dentate gyru is found at the C-shaped region of the hippocampus. And so, to understand human depression, researchers performed an experiment on rats. The rats were induced with depression like symptoms. A blasting static noise was tested on the animal at unpredictable intervals for several weeks. The results showed that the stressed rats were unable to swim in a tank indicating their “feelings of hopelessness.” To observe further in their experiment, the researchers compared the rat’s brain activity between a depressed and normal rat. In this case, the rat’s brains were analyzed by extracting their brains in slices and then placed in voltage-sensitive dye with electrode to observe under a high-speed camera.










Source: http://www.brain.riken.jp/bsi-news/bsinews2/no2/issue2e.html

This figure is just to show an example of what the process would look like when a high-speed camera is used to observe hippocampus activity . "The activities in the hippocampal CA1 region using an ultrahigh-speed camera developed in Dr. Michinori Ichikawa's laboratory. This shows the activities after high-frequency stimulation was applied by modeling the learning process. Long-term potensiation phenomenon of the hippocampal CA1 region captured on potential-sensitive dyes using a high-speed camera."

The high-speed camera is mainly used to observe hippocampus activity. They found “a smaller aura of activity originating from the curved dentate gyrus than in normal rats.” In their previous research, they found that a depressed rat treated with fluoxetine (Prozac) experienced more rapid neurogenesis. In addition, “the range of electrical signals from their dentate gyri spread as far as in normal rats.” All in all, they learned that the hippocampal activity is involved in depressed behavior. However, they were not able to identify the origin of the problem within the hippocampus. And so, the causes of depression remained a mystery.

I found this article interesting because I have performed an experiment on rats in the past. It’s amazing how a small animal can be helpful in understanding human behavior. Yet, some remains a mystery to us when it comes to understanding how behavior is triggered in the brain and how it is processed. The brain is a very complex structure that often times it is difficult for researchers to identify where a specific behavior is triggered or originated from.

Related link:
Soluble oligomers of b amyloid (1-42) inhibit long-term potentiation but not long-term depression in rat dentate gyrus.