[N400: an electrophysiological measure of semantic processing]

The aim of this study was to survey the information available regarding the N400 component of event related potentials (ERP) as an electrophysiological measure of semantic processing.

The N400 component of ERP is characterised, the advantages and disadvantages of studies that use this type of electrophysiological measures are presented, and the main findings of the experiments conducted in recent years to establish how N400 is related to linguistic processes are analysed. We also present some of the ways its study can be applied to understanding the brain processes underlying dementias, and especially Alzheimer s disease. The value of this component of ERP in the scientific study of mental processes is clearly illustrated.

Electrophysiological measures of ERP are a very promising tool for the study of the cognitive processes that sustain the understanding and organisation of language and memory. ERP are changes in voltage that are registered on the scalp and which are synchronised with an observable (sensory, motor or cognitive) event. They are a non invasive method of monitoring brain processes in real time and as such can be used to obtain electrophysiological evidence of brain functioning and of psychological processes. The N400 component of ERP has been linked mainly to language processing and has been recorded in association with examples of semantic incongruence found in sentences, words or visually presented figures.