Tag: propranolol

Erasing a memory reveals the neurons that encode it

By Ed Yong | March 12, 2009 2:00 pm

Blogging on Peer-Reviewed ResearchA couple of weeks ago, I wrote about propranolol, a drug that can erase the emotion of fearful memories.  When volunteers take the drug before recalling a scary memory about a spider, it dulled the emotional sting of future recollections. It’s not, however, a mind-wiping pill in the traditional science-fiction sense, and it can’t erase memories as was so widely reported by the hysterical mainstream media.

Neurons.jpgThe research that’s published today is a different story. Jin-Hee Han from the University of Toronto has indeed found a way to erase a specific fearful memory, but despite the superficial similarities, this is a very different story to the propranolol saga. For a start, Han worked in mice not humans. And unlike the propranolol researchers, who were interested in developing ways of treating people with post-traumatic stress disorder, Han’s goal was to understand how memories are stored in the brain. Erasing them was just a step towards doing that. 

Han’s found that a protein called CREB is a molecular beacon that singles out neurons involved in remembering fearful experiences. When a rat experiences something scary, the CREB-neurons in a part of its brain called the amygdala are responsible for storing that memory – for producing what neuroscientists call its “trace”. When Han killed the amygdala’s CREB-neurons, he triggered selective amnesia in the rats, abolishing the specific fears they had been trained to feel. The memory loss was permanent.

This is a major piece of work. Scientists have long believed that memories are represented by specific collections of neurons. But these neurons don’t occur in a neat, tidy clump; they’re often widely spread out, which makes finding the cells that make up any particular memory incredibly challenging. Han has done this by using the CREB protein as a marker. And in doing so, he had highlighted the vital role of this protein in our memories.

I stress again that this isn’t about erasing memories in and of itself. Doing so is just a means to an end – identifying a group of neurons involved in storing a specific memory. For reasons that should become clear in this article, Han’s technique isn’t exactly feasible in humans! Whether this will stop the inevitable run-for-the-hills editorials is perhaps unlikely, but enough speculation: on with the details.

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