In the longer term, new treatments for devastating brain diseases are likely to emerge from a deeper understanding of brain circuits. Truly understanding a circuit requires identifying and characterizing the component cells, defining their connections with one another, monitoring and recording their activity patterns – and we are still at the point where much work remains to identify the key differences in a vast array of unknown neurons. Researchers continue to explore the mechanics behind a healthy brain that functions quickly and automatically – at the speed of thought. However, due to the vast complexity of the brain, much remains to be discovered. Remodeling its circuitry with each new experience – our brain makes us who we are, enabling us to perceive beauty, teach our children, remember loved ones, react against injustice, learn from history, and imagine a different future. All human brains share basic anatomical circuits and synaptic interactions, but the precise pattern of connections and interactions are highly variable from person to person-and therein lies the source of the remarkable variation we see in human behavior – from the breathtaking dance of a ballerina, to the elegant craftsmanship of a master carpenter, to the shrewd judgment of an expert trader. Over hundreds of years, scientists have learned much about the brain, including the countless methods through which information is transferred from neuron to neuron at a junction called a synapse, and how hundreds – even thousands – of neurons can function together to form a larger circuit responsible for any given activity. The average brain contains 80-90 billion neurons, the cell bodies of which form “gray matter.” Many, many more specialized cells called “glia” protect and support neurons in gray matter, and provide insulation for their delicate interconnections (called axons) in the “white matter.” The folds in the human brain form sulci (grooves) and gyri (ridges), adding to its surface area to maximize the number of cells that can pack into our skulls, and increasing the quantity of information we can process.
All sensations, movements,, memories, and feelings are the result of signals that pass through neurons of differing shapes, sizes, and functions. The brain and the rest of the central nervous system are composed of a variety of cells, but the primary functional unit is a cell called a neuron.
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