The great subjective back-referral debate: Do neural responses increase during a train of stimuli?

Evidence is summarised for and against the hypothesis that potentiation or facilitation of neural responses during a train of threshold-level stimuli occurred in the experiments reported by Libet et al. (1964). It is concluded that such potentiation probably did occur. Since the main arguments for the existence of subjective backwards referral (Libet, Wright, Feinstein, & Pearl, 1979) take it as given that such potentiation did not occur, it is further concluded that the main arguments for the existence of subjective backwards referral fail.