What is the output of the transient electrical activity measured by an EEG?

The output of transient electrical activity measured by an electroencephalogram (EEG) is electrical potential differences. EEG works by placing electrodes on the scalp to detect the electrical activity generated by neurons in the brain. These neurons communicate through electrical impulses, and the EEG captures these activities as variations in voltage over time.

In essence, the EEG provides a real-time graphical representation of brain activity based on the summation of these electrical signals from multiple neurons. The signals appear as waveforms that can be analyzed to understand various brain states, such as sleep, wakefulness, and responses to stimuli.

In contrast, magnetic fields are related to magnetoencephalography (MEG) and not directly measured by EEG. Nerve impulses do reflect electrical activity at a cellular level but are not what is captured directly by an EEG, as the EEG measures the field potentials created by large groups of synchronized nerve impulses. Chemical signals, while critical for neurotransmission and communication in the nervous system, are not what EEG measures; it focuses specifically on electrical properties.

The choice of electrical potential differences is therefore the most accurate representation of the data captured by an EEG.