Which device records the electrical activity of the brain using electrodes placed on the scalp?

The device that accurately records the electrical activity of the brain using electrodes placed on the scalp is the electroencephalogram (EEG). This technique involves attaching multiple electrodes to the scalp, which detect the electrical impulses generated by neurons as they communicate with each other. The EEG provides valuable real-time data reflecting the brain's activity, allowing researchers and clinicians to study various brain functions, diagnose conditions like epilepsy, sleep disorders, and monitor brain activity during surgical procedures.

In contrast, the other imaging techniques mentioned serve different purposes. Magnetic Resonance Imaging (MRI) is used to create detailed images of organs and tissues in the body, particularly the brain, but it does not directly measure electrical activity. A Computed Tomography (CT) scan provides images of the brain structure and can identify abnormalities, but it also does not capture the real-time electrical activity of the brain. Lastly, Positron Emission Tomography (PET) measures metabolic processes in the brain by using radioactive tracers, giving an indirect reflection of brain activity rather than directly recording electrical signals. Each of these methods has unique applications, but for tracking electrical activity specifically, the EEG is the appropriate choice.