Comparison of Midlatency Auditory Sensory Gating at Short and Long Interstimulus Intervals

Abstract

Rationale: Suppression of P50, N100 and P200 auditory evoked responses in a dual-click procedure is considered an index for the multistage sensory gating process. Whereas most studies use a protocol with long interstimulus intervals of 8–12 s between the stimuli pairs, there is also evidence that sensory gating occurs at much lower intervals. The aim of the study was to investigate whether a simple modified dual-click protocol with short interstimulus intervals elicts similar sensory gating ratios compared to the classic protocol. Methods: P50, N100 and P200 amplitudes and sensory gating ratios were measured in 23 healthy subjects with 2 different dual-click protocols in 1 session: (1) a simple oddball modified with short interstimulus intervals of about 2.8 s (ISI2), and (2), the classic used with long intervals of about 8 s (ISI8). Results: The amplitudes of the P50, N100 and P200 responses were mostly comparable and correlated between both protocols. Mean sensory gating ratios (ISI8/ISI2) were as follows: P50, 35.4/36.4%; N40P50, 36.1/39.9%; N100, 44.4/48.4%; P200, 46.8/43.3%; N100P200, 45.3/41.8%; all differences between protocols, p > 0.1. P50 ratio scores did not show a sufficient correlation between protocols [intraclass correlation coefficient (ICC) P50, 0.13; N40P50, 0.0] compared to N100 (ICC, 0.79), P200 (ICC, 0.6) and N100P200 (ICC, 0.61). Conclusion: Our results contradict the assumption that long interstimulus intervals of about 8 s are absolutely necessary to elicit a marked sensory gating phenomenon for P50, N100 and P200 auditory responses (at least when using a protocol with a simple attention task). However, because only healthy subjects were investigated, no prediction can be made for psychiatric patients, in whom neuronal processing may be different.