When Richard Caton first measured fluctuations on a voltmeter from electrodes placed on the scalp of a human subject, he was recording what we now call:

A) an electroencephalogram.
B) the action potential.
C) a magnetoencephalogram.
D) axonal conductance.

Electroencephalogram

A diagnostic test that measures electrical activity in the brain using small electrodes attached to the scalp.

Richard Caton

A British physician who pioneered the study of electrical activity in the brain, leading to the development of electroencephalography.

Axonal Conductance

The process of transmitting electrical impulses along the axon of a neuron.