Any anomaly of brain-evoked potentials, defined as potentials generated by exteroceptive stimuli reflect synchronized activity by neuronal and axonal groups in the central nervous system (CNS) resulting from the arrival of nerve impulses after stimulation of a peripheral nerve or its receptors. Depending on the type of stimulus, evoked potentials are categorized as visual (VEP), auditory (AEP), or somatosensory (SSEP). Motor evoked potentials (MEP) occur when the brain's motor area is stimulated. They result from the activation of a sufficient number of motor units. [from
HPO]