[Contingent negative variation elicited by electrical taste stimulation]

Contingent negative variation (CNV) was elicited using electrical taste stimulation as the warning stimulus. Stimuli were generated for 100 msec or 500 msec using a bipolar stainless steel electrode disc with the center portion acting as the anode and the outer portion as the cathode. The imperative stimulus was a pure tone of 1 kHz at 60 dB and the interstimulus interval of paired stimuli was 2000 msec. The electrode was gently held in contact with the tongue by a specially made fixture and electrical taste stimuli were presented at 5-sec intervals. The CNV was recorded in 10 normal subjects at the Cz site of the 10-20 International System, referred to linked earlobes with a forehead ground. The results from 20 presentations were averaged. The mean threshold measured by electrogustometry employing a monopolar electrode as the anode was -4.2 dB (0 dB = 8 microA), and the mean thresholds measured with the bipolar electrode at a stimulus duration of 100 msec and 500 msec were 0 dB and -1.4 dB, respectively. As the mean threshold obtained with a duration of 500 msec was closer to the electrogustometry findings than that obtained with a duration of 100 msec, a stimulus duration of 500 msec was useful for determining the CNV threshold. The CNV could be recorded in all 10 normal subjects, and the late component was conspicuous because of recording at the Cz site. In four subjects, the P300 could be recorded after the warning stimulus at an intensity of 40 microA.(ABSTRACT TRUNCATED AT 250 WORDS)