In a recent study by Joseph LeDoux, it has been found that memories associated with fear can be altered or completely erased from the long-term memory. The memory is comprised of three main parts. The sensory register includes anything picked up by your senses. From here, anything that you pay attention to will be transferred into the short-term memory, which can hold five to nine items at a time. The long-term memory has an endless capacity. It's a little bit harder for memories to end up here, though, since it requires the synthesis of new proteins along with structural changes to nerve cells.
             Until Joseph LeDoux conducted his experiment, it was believed that memories stored in the long-term memory were, for the most part, permanent and hard to disrupt. LeDoux used Pavlov's conditioning techniques to train rats to become fearful when they hear a certain tone. He did this by providing a mild electrical shock to the rats' feet at the same time that the tone was played. One training session was enough to teach the rats that the tone meant pain, and they would freeze with fear upon hearing it.
             Once the rats were conditioned, LeDoux played the tone again, but this time, at the moment when the rats would remember the shock, he injected the rats' amygdalas with an antibiotic that stops the synthesis of new proteins. A day later he tested the rats again by playing the tone, only to find that the majority of them didn't react. After numerous tests he realized two things. One, this "fear amnesia" occurs only when the injection and the reactivation of the memory happen at the same time, and two, it doesn't matter how old the memory is.
             LeDoux has earned merit for the theory that memories go through a vulnerable stage and can be altered. Although his research hasn't shed any light on memories other than fearful ones, it has raised many questions about--and opened the door for
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