Two different components of contingent negative variation (CNV) and their relation to changes in reaction time under hypobaric hypoxic conditions.

Abstract

BACKGROUND: Acute hypoxic conditions cause deterioration of the higher cerebral functions. The contingent negative variation (CNV), which represents both psychological and motor functions, is useful in evaluating cerebral functions. However, few attempts have been made to understand CNV change, especially for components under acute hypoxic conditions. HYPOTHESIS: If recognition of stimulus is affected by acute hypoxic conditions, the CNV response may be decreased and reaction times (RTs) may be prolonged. In addition, the differing effects of hypoxia on the early and late CNV would be demonstrated. METHODS: Hypobaric hypoxic conditions at altitudes of 0-6000 m were simulated in an experimental decompression chamber, at a decompression speed of 110 m x min(-1). Peak amplitudes of the entire, early and late CNV were measured at each altitude together with RT measurements. RESULTS: At 6000 m, the complete CNV decreased significantly compared with that at 0 m (p<0.01). Early CNV also showed a significant decrease (p<0.05), but there was no significant change in late CNV. The RTs were prolonged significantly at 5000 and 6000 m (p<0.05, p<0.01). At the altitudes of 3000 and 0 m, a negative correlation between the peak amplitude late CNV and the RT was recognized statistically (p< 0.01), while at 4000 m and above, it was rather the early CNV and the RT that were negatively correlated (p<0.01). CONCLUSIONS: With interstimulus intervals of 2 s, acute hypoxia served to reveal the functional properties of the early and late components of CNV. CNVs may be regarded as good indexes of higher cerebral function under hypoxic conditions.