Comparison of χ² between single- and double-Gaussian fittings for cells with significant effects of duration in the ANCOVA for the visual (A) and auditory (B) conditions. , where O_i is observed discharge rate and E_i is expected discharge rate for trial i. For single-Gaussian fittings, the discharge rate across trials and sequence order was the dependent variable, and target interval was the independent variable, using Equation 3. For the double-Gaussian fittings, the discharge rate computed for each interval and sequence order across trials was the dependent variable, and interval and sequence order were the independent variables, using Equation 5. In both fittings, we used 150 trials: 5 intervals × 6 sequence orders × 5 trials. The dotted line corresponds to the diagonal, and below the continuous horizontal, the cells showed a significant fitting on the χ² test (p < 0.05). It is evident that the double-Gaussian model showed smaller χ² and better fittings than the single-Gaussian model.