The role of the sulcus in brain anatomy pertains to the grooves or indentation on the brain's surface, which increases the surface area of the cerebral cortex. This expansion allows for a greater number of neurons and synapses, facilitating more complex cognitive functions such as reasoning, problem-solving, and emotional regulation. The arrangement of sulci and gyri (the raised portions) helps define various brain regions associated with specific activities, contributing to the overall functioning of the nervous system.