The study of the anatomy and operation of the nervous system and the brain is known as neuroscience. To map the brain mechanistically, neuroscientists draw on cellular and molecular biology, anatomy and physiology, human behavior and cognition, and other fields.<br /><br />Each neuron, or brain cell, in an adult human has an estimated 100 billion connections to other neurons. The mapping of all the cell-to-cell communication networks&mdash;the brain circuits that process all ideas, feelings, and behaviors&mdash;remains one of the major difficulties of contemporary neuroscience. The resulting image that gradually forms is referred described as &quot;the connectome.&quot; All learning is based on the brain&#39;s capacity to build new neural circuits and connections, or neuroplasticity.