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Tuesday, 17 February 2009
Propranolol and fearful memories
Under certain carefully contrived circumstances, there is growing evidence that propranolol (a beta-blocker) can erase fearful memories. More accurately, it seems that propranolol can almost entirely remove the fearful aspect of the memory, whilst preserving its other aspects.
Her team recruited 60 students and conditioned them to fear images of spiders, by pairing the pictures with uncomfortable electric shocks. A day later, they showed them the same pictures and measured how strongly they blinked in response to a loud noise. These responses are called "startle reflexes" and they reflect activity in the amygdala and whether a person is in a fearful state of mind. Sure enough, the students were more easily startled by the noise if it was accompanied by the electrifying spider pictures than images they hadn't learned to fear.
On this second day, Kindt gave some of the recruits 40 milligrams of propanol [sic] about 90 minutes before they were tested again. The others were given a placebo, but both groups reacted in the same way. Both of them could remember the fearful nature of the spider visuals, showing that the drug didn't affect their ability to recall their old memory.
Two days later, and things were very different. Now, Kindt found that the while the volunteers on the placebo still feared the spiders, those who had been given propanolol [sic] no longer did. In fact, they were as difficult to startle as volunteers who had been conditioned in the first place. The drug had completely eliminated their fear response.
The nice thing about these experiments is that they promise an eventual aid to people with things like post-traumatic stress disorder, whereby they might be helped to get on with their lives - despite still remembering the details of the event. I don't know about you, but I'd feel much more comfortable with only the fearful aspects stripped off a particularly debilitating memory, rather than erasing the entire memory wholesale.
Anyway, read more about it here (it's where the above quote is from).