‘Sensing, perceiving, and acting’ investigates how the brain processes and acts upon sensory information. Visual information is sensed by retinal cells before travelling down the optic pathway to the primary visual cortex, before travelling to the extra-striatal visual areas. The mechanisms of visual recognition are currently a source of heated debate. Visual information is used to drive saccadic eye movements in the superior colliculus. The direction of certain frequencies of sound are processed in the medial superior olive, which measures the time between sound reaching each ear. In the muscles, muscle spindles monitor muscle length and allow for subconscious control of muscular activity via the spinal cord.