Article Figures & Data
Figures
- Figure 1.
Direction discrimination task with brief motion pulses. Subjects were asked to identify the direction of motion in a dynamic random dot display, presented in one or two 120 ms epochs. The strength of motion was randomized across trials and between the motion pulses, but the direction of motion (left or right) was the same for both pulses on double-pulse trials. The interval between pulses ranged from 0 to 1.08 s. See Materials and Methods.
- Figure 2.
Choice accuracy in double-pulse trials was independent of the interpulse interval. A, Accuracy in single-pulse trials. The curve is the fit of a logistic function (Eq. 1) to the data. B, Accuracy in double-pulse trials with same pulse strengths. Horizontal lines show the expected accuracy of a perfect integrator based on the single-pulse performance. Arrows show the value of the logistic fit for single-pulse trials of similar motion strength. C, Accuracy in double-pulse trials with different pulse strengths. Each data point represents pooled data from the pulse sequence indicated by the legend and its reverse order (e.g., 3.2–6.4% and 6.4–3.2%). Horizontal lines show the expected accuracy of a perfect integrator based on single-pulse performance. Error bars indicate SEM. coh, Coherence.
- Figure 3.
Choice accuracy depended on the sequence of motion pulses. Probability correct for double-pulse trials with unequal pulse strength was calculated by pooling data across all intertrial intervals. Overall, the weak–strong pulse sequence resulted in higher accuracy than the strong–weak sequence. Error bars indicate SEM. *p < 0.05, **p < 0.01.
- Figure 4.
The second pulse had the larger influence on choice. Each panel shows the average motion energy profiles for the first and second pulses, sorted by choice. Only trials with equal pulse strength are included. The shaded region around the mean indicates SEM. The black horizontal bars show the stimulus presentation period. Data were pooled for all nonzero interpulse intervals. Motion coherences are indicated at the top of each panel: A, 12.8%; B, 6.4%; C, 3.2%. The units of motion energy are arbitrary, but are identical for all motion strengths. The degree of influence on choice can be ascertained by comparing the energy accompanying correct and erroneous choices (red and blue, respectively).
Tables
- Table 1.
Performance was largely unaffected by interpulse interval for double-pulse trials with equal pulse strength and with unequal pulse strength
Subjects Equal strength Unequal strength β3 β4 β3 β4 β5 S1 −0.52 ± 0.40 (p = 0.18) 5.1 ± 6.3 (p = 0.41) 0.26 ± 0.51 (p = 0.61) −0.25 ± 4.0 (p = 0.95) −2.0 ± 4.1 (p = 0.63) S2 −0.59 ± 0.38 (p = 0.12) 4.5 ± 5.4 (p = 0.41) −0.001 ± 0.48 (p = 0.99) 3.8 ± 3.6 (p = 0.29) −3.1 ± 3.8 (p = 0.42) S3 −0.75 ± 0.38 (p = 0.05) 9.5 ± 5.3 (p = 0.07) 0.33 ± 0.50 (p = 0.51) 6.5 ± 3.9 (p = 0.09) −8.1 ± 3.9 (p = 0.04) S4 0.27 ± 0.44 (p = 0.54) −3.1 ± 6.1 (p = 0.61) −0.28 ± 0.54 (p = 0.60) 0.70 ± 4.1 (p = 0.87) 4.4 ± 4.3 (p = 0.31) S5 0.39 ± 0.41 (p = 0.35) −4.4 ± 5.6 (p = 0.43) 0.01 ± 0.51 (p = 0.99) 1.3 ± 4.0 (p = 0.75) −0.52 ± 4.0 (p = 0.90) Each row shows the coefficients of Equation 3 (mean ± SE) and their associated p values.
