Experiments indicate propranolol also blocks the effect of adrenaline upon areas of the brain involved in memory formation, including the amygdala. It seems to disconnect emotion from memory.
In a study conducted by Larry Cahill, a neurobiologist at UC Irvine, McGaugh and others in the late 1990s, test subjects were told an emotionally neutral, comparatively boring story illustrated by 12 slides. A second group of subjects was then shown the same 12 slides. The related story, however, was much more emotional, involving a severely injured boy.
When later asked what they remembered seeing in the pictures, subjects in the second group recalled much greater detail about the story than the first group did about theirs.
Cahill and McGaugh then presented the second, emotionally upsetting story with slides to a third group of volunteers who were given a standard dose of propranolol or endurol (another beta blocker). Their memories, when tested three weeks later, were "just like that of subjects who had received the boring story," said McGaugh.
Subjects remembered the story, but without any emotional depth.
Such findings suggest an obvious potential therapeutic benefit: If people who have just experienced a traumatic event could be given a memory-dampening drug like propranolol, they might avoid suffering later psychic damage, such as post-traumatic stress disorder or PTSD.