Which medical test assesses brain electrical activity?

The correct answer is the electroencephalogram (EEG), which is a medical test specifically designed to measure and assess the electrical activity of the brain. This test involves placing electrodes on the scalp that detect electrical impulses produced by the brain's activity, allowing healthcare professionals to evaluate brain function, identify abnormalities, and diagnose conditions such as epilepsy, sleep disorders, and other neurological issues.

The other methods mentioned serve different purposes. Magnetic resonance imaging (MRI) provides detailed images of the brain's structure but does not measure brain electrical activity. Cerebrospinal fluid analysis is a diagnostic procedure that examines the fluid surrounding the brain and spinal cord, often used to identify infections or inflammatory conditions. A lumbar puncture, also known as a spinal tap, is a procedure used to collect cerebrospinal fluid for testing but does not assess electrical activity in the brain. Thus, the electroencephalogram is the only test among the options provided that specifically evaluates brain electrical activity.