Which of the following is NOT a function of the brainstem?

The brainstem plays a crucial role in controlling several vital autonomic functions, including heart rate, sleep regulation, and managing arousal. It is responsible for processing essential life-sustaining functions, such as involuntary actions like breathing and heart rate regulation, along with contributing to the sleep-wake cycle and levels of arousal and wakefulness.

However, processing visual information is primarily a function of the visual cortex located in the occipital lobe of the brain. While brainstem structures may play a minor role in certain reflex actions related to vision (such as pupil response), the detailed processing and interpretation of visual stimuli are not handled by the brainstem. This distinction highlights why the processing of visual information is not a function of the brainstem, making it the correct choice here.