The explosion in neuroscience is slowly revealing the mechanisms of cognition. �We have accumulated enough knowledge about the mechanisms and molecular underpinnings of cognitionat the synaptic and circuit levels to say something about which processes contribute,� says James Bibb of the University of Texas Southwestern Medical Center, who organized a symposium on �cognitive enhancement strategies� at the 2010 meeting of the Society for Neuroscience. Greater cognitive capacity comes from having more neurons or synapses, higher levels of neurogenesis (the creation of new neurons, especially in the memory-forming hippocampus), and increased production of compounds such as BDNF (brain-derived neurotrophic factor), which stimulates the production of neurons and synapses, says neuroscientist Yaakov Stern of Columbia University. Both neurogenesis and synapse formation boost learning, memory, reasoning, and creativity. And in people who excel at particular tasks, Stern�s neuro-imaging studies show, brain circuits tend to be more efficient (using less energy even as cognitive demand increases), higher capacity, and more flexible.

One of the strongest findings in neuroplasticity, the science of how the brain changes its structure and function in response to input, is that attention is almost magical in its ability to physically alter the brain and enlarge functional circuits. In a classic experiment, scientists found that when monkeys repeatedly practiced fine-tactile perception, the relevant brain region expanded, just as it does when people learn Braille or the violin. Similarly, a region of the auditory cortex expands when we hear a particular tone over and over. (Yes, the spot that processes your ringtone is encroaching on next-door areas.) But when monkeys simultaneously touched something and listened to tones, only the brain region controlling the input they were trained to focus on expanded. In other words, identical input�tactile sensations and sounds�produces a different result, expanding a brain area or not, depending only on whether attention is being paid.