Research at Montreal Neurological Institute and Hospital (The Neuro) of McGill University has shown that different patterns of training and learning lead to different types of memory formation. In every organism they studied, researchers reported that formation of memories is highly sensitive not only to the total amount of training but also to the pattern of trials used during training. Specifically, spaced training (distributed over time) is superior at generating long-term memories as compared to massed training (at very short intervals). "It is a well known psychological principle that learning is better when training trials are spaced out than when given all together," says Dr. Wayne Sossin, neuroscientist and lead investigator. This study identified differences between the two types of training at the molecular level. Interestingly, the process of strengthening communication between nerve cells (neurons), called synaptic facilitation, is controlled by the release of the neurotransmitter serotonin.