What is measured by Electroencephalograms (EEGs)?

Electroencephalograms (EEGs) are primarily used to measure neural activity by recording electrical impulses generated by the neurons in the brain. This technique involves placing electrodes on the scalp that detect the signals produced by the electrical activity of brain cells. The resulting data is then displayed as waveforms that represent the brain's electrical activity over a period of time.

EEGs are particularly valuable for studying brain function, diagnosing conditions such as epilepsy, and understanding various states of consciousness. The electrical activity captured in an EEG can reveal important information about how different areas of the brain communicate and operate during various tasks or resting states.

In contrast, the other choices pertain to different methodologies or types of information not measured by EEGs. For instance, blood flow in the brain is typically assessed through techniques like functional MRI or PET scans, while structural changes in the brain are measured using imaging modalities such as CT or MRI scans. Magnetic activity in neurons is more relevant to techniques such as magnetoencephalography (MEG), which is distinct from the electrical measurements taken by EEGs.