A concept of consciousness

The term "consciousness", so widely used in clinical settings, is considere d extremely complex and practically undefinable. Historically, consciousnes s was ignored by the great classical philosophers, and was regarded as a ba sic condition of "being". This changed with Descartes and during the ensuin g centuries. A simplified, reductionistic and easily definable concept of c onsciousness is proposed; consciousness is proposed to consist of three mai n components: vigilance, mental contents, and selective attention. These three components can be investigated with modern neuroscientific meth ods - vigilance being the most readily explorable function. The striking di fferences between sleep and coma are pointed out (along with some observati ons on sleep initiation). Special attention is paid to epileptic impairment of consciousness and, in particular, to the spike-wave absence which is th ought to be due to a temporay suspension of the "working memory circuits" w ithin the frontal lobe.