Frequency-component analysis for CRs as a function of CS-US intervals in a delay paradigm. A, From top to bottom are illustrated the conditioning paradigm, representative examples of the EMG activity of the orbicularis oculi muscle (O.O. EMG), and eyelid position, velocity, and acceleration during the paired presentation of the CS followed 500 ms later by the US. B, Evolution of the percentage of CRs (% CRs ± SEM) through the 10 conditioning sessions for five delay conditioning paradigms of different CS-US interval: 50 ms (○), 250 ms (□), 500 ms (■), 1000 ms (▵), and 2000 ms (•). Note that animals conditioned with 250 or 500 ms CS-US intervals reached asymptotic values (80% of CRs) by the fourth to sixth conditioning sessions, but that those trained with the other three intervals failed to reach criterion by the 10th conditioning session. Data collected for intervals of 250 and 500 ms were not statistically different, but were significantly (one-way ANOVA on ranks, p = 0.17) different from those conditionings performed with the other three CS-US intervals. Pairwise multiple-comparison analysis, Holm–Sidak method: ♦p < 0.001 for □ versus ○, ▵, and •. ♢p < 0.001 for ■ versus ○, ▵, and •. *p < 0.001 for ▵ versus ○ and •. C, Illustration of the mean spectral power from ≥30 acceleration records (n = 4 rabbits) of eyelid reflex responses to air puffs (100 ms, 3 kg/cm²) presented to the ipsilateral cornea. The 100% value for the illustrated spectral power corresponded to 0.93 × 10⁷ (deg/s²)², with a peak frequency of 12 Hz. D, Mean spectral powers (≥10 acceleration profiles) of CRs evoked during the five different CS-US intervals illustrated in B (1, 50 ms; 2, 250 ms; 3, 500 ms; 4, 1000 ms; 5, 2000 ms). Each mean spectral power was obtained from two different rabbits. The 100% value for the illustrated spectral power corresponded to 0.3 × 10⁷ (deg/s²)². Peak frequencies for the different CS-US intervals were ≈12 Hz.