Article Figures & Data
Figures
- Figure 1.
Stimulus and serial order of the trials from the different conditions. A, Each trial presented a forward displacement across a ground plane simulated by an optic flow stimulus. First, a passive trial was presented. In the passive condition the fixation target was red. The ground plane stimulus, consisting of random white dots, was presented stationary for 700 ms. Then the dots moved for 600–1525 ms depending on the speed (slow or fast) and distance (short, medium or long) simulating forward self-motion (represented by the blue arrow). After movement offset, the ground plane was displayed stationary for another 700 ms before the screen turned black. This triggered an intertrial-interval (ITI) lasting between 750 and 1250 ms. Next, an active trial was started, indicated by a green fixation target. Participants were asked to reproduce double the previously observed passive distance using a gamepad. Self-motion was controlled by deflecting a joystick. After movement offset the ground plane was again presented stationary for 700 ms. The movement (speed profile) was recorded and played back in the replay condition. Here, the fixation target was white, and participants were just asked to observe the self-motion stimulus. B, Three pairs of a passive (red fixation target) and an active trial (green fixation target) each were shown before the corresponding three replay movements were presented in pseudo-randomized order.
- Figure 2.
Single participant’s (participant 4) velocity profiles in active trials and the mean of those velocity profiles as well as the mean of the gradient of each velocity profile for all participants. Panels A and B show data from a single participant (participant 4). In contrast, panels C and D show the mean data of all 15 participants. The green lines in A and B represent the velocity profiles. In A, aligned to the onset of the trial (presentation of the ground plane) at t = 0 s, in B, aligned to t_sub, the time passing the subjective single distance (t = 0 s). The data shown in A were recorded in active trials after the presentation of passive trials with low speed and the shortest distance. The velocity profile of the passive condition is depicted in red. In the passive condition, simulated self-motion always started 0.7 s after trial onset. Participants were free to start the movement as soon as they preferred in the active trials. This leads to an earlier increase in speed in some of the active trials as compared with the passive trials. Panel B presents the velocity profiles of all active trials recorded for this participant in green, as well as the mean of those profiles in black and the mean with the added and subtracted SDs in gray. Panels C and D show mean values for each of the 15 participants. In C, the means over all velocity profiles are presented; in D, the means over the respective temporal derivative (acceleration).
- Figure 3.
Distance reproduction performance. Bars show the reproduced distances in the active condition for all 15 participants. The mean distance (two times d_sub) over all trials is presented for each participant (error bar: SD). Data are shown for the three passive distances (short, medium and long). The horizontal black solid line in each plot represents double the passive distance, i.e., the required response 2*d_obj. The panel in the lower right depicts the average performance across all participants. The required response is shown in a checkerboard pattern whereas the average response, resulting in an overshoot, is shown in white.
- Figure 4.
Visual evoked potentials (VEPs) elicited by self-motion onset and offset. Data from electrode clusters F (electrodes Fz, F3, F4), C (electrodes Cz, C3, C4), P (electrodes Pz, P3, P4), and O (electrodes Oz, O1, O2) are shown for the three conditions: passive (red), active (green), and replay (black). In the left column, time 0 ms represents self-motion onset, while in the right column, it represents self-motion offset. In all panels, negative voltages are plotted upward on the y-axes.
- Figure 5.
Amplitude differences and latencies of the components P1, N2, and P2 for self-motion onset VEPs of the F cluster. Panels depict data from the active and replay condition (left column), active and passive condition (middle column), and replay and passive condition (right column). Each dot in each panel depicts data from a single subject. In the top row, we present the differences |P1-N2| (purple) and |P2-N2| (yellow) for the different conditions. In the bottom row the peak times for the three components P1 (cyan), N2 (magenta) and P2 (blue) are shown. In all six panels, the mean values of each group of data with the corresponding SDs are presented as a cross.
- Figure 6.
Amplitude differences and latencies of the components P1, N2, and P2 for self-motion onset VEPs of the C cluster. Conventions as in Figure 5.
- Figure 7.
Amplitude differences and latencies of the components P1, N2, and P2 for self-motion onset VEPs of the P cluster. Conventions as in Figure 5.
- Figure 8.
Amplitude differences and latencies of the components P1, N2, and P2 for self-motion onset VEPs of the O cluster. Conventions as in Figure 5.
- Figure 9.
Amplitude differences and latencies of the components P1, N2, and P2 for self-motion offset VEPs of the P cluster. Conventions as in Figure 5.
- Figure 10.
Amplitude differences and latencies of the components P1, N2, and P2 for self-motion offset VEPs of the O cluster. Conventions as in Figure 5.
- Figure 11.
Permutation tests between data recorded in the active and replay conditions for the alignments to t_sub and t_obj averaged over all 14 participants. The panels depict data from the subjective (t_sub; left column) and the objective (t_obj) alignment (right column). The eight panels depict the results of the permutation tests with data recorded from the F, C, P, and O shown from top to bottom. In bright colors, clusters with p-values smaller than p = 0.01 are presented. In all panels, data recorded in active trials are contrasted with data recorded in replay trials.
Tables
Participant # 1 2 3 4 5 6 7 8 t_sub [ms] 1226 (±348) 1380 (±379) 1131 (±368) 1312 (±493) 867 (±287) 1362 (±425) 1229 (±379) 1188 (±294) Difference: t_sub –
t_obj [ms]237 (±289) 152 (±245) 161 (±216) 261 (±299) 34 (±164) 25 (±318) 111 (±205) 48 (±169) Difference: t_sub –
t_1/2_fulltime [ms]34 (±75) 93 (±85) 88 (±98) 36 (±58) 12 (±31) 61 (±80) 43 (±66) 64 (±53) Participant # 9 10 11 12 13 14 15 t_sub [ms] 1061 (±339) 1312 (±403) 501 (±119) 1141 (±361) 1271 (±337) 646 (±141) 1089 (±425) Difference: t_sub –
t_obj [ms]6 (±294) 307 (±280) −110 (±382) 272 (±279) 231 (±277) −78 (±254) 206 (±307) Difference: t_sub –
t_1/2_fulltime [ms]39 (±67) 132 (±97) −10 (±23) 43 (±61) −4 (±64) 17 (±27) 97 (±139) Travel times for half the traveled distance (t_Sub), the difference between the times traveled to reach half of the subjective and the objective distance (t_sub – t_obj), and the difference between the times traveled to reach half of the subjective distance and half of the time traveled (t_Sub – t_1/2_fulltime). Values show the averages over all trials and the respective SDs.
Self-motion onset: F cluster Self-motion onset: C cluster Active Replay Passive Active Replay Passive Latency Latency Latency Latency Latency Latency P1 111 ms 114 ms 94 ms 111 ms 114 ms 94 ms N2 153 ms 156 ms 136 ms 153 ms 156 ms 136 ms P2 243 ms 241 ms 236 ms 250 ms 250 ms 236 ms Amplitude Amplitude Amplitude Amplitude Amplitude Amplitude |P1-N2| 0.79 μV 1.13 μV 1.28 μV 1.43 μV 1.81 μV 1.92 μV |P2-N2| 2.51 μV 2.94 μV 3.57 μV 2.32 μV 2.82 μV 3.36 μV Latencies and amplitude differences for the P1, N2, and P2 components for the three conditions (active, replay, and passive) for self-motion onset.
Self-motion onset: P cluster Self-motion offset: P cluster Active Replay Passive Active Replay Passive Latency Latency Latency Latency Latency Latency P1 111 ms 113 ms 96 ms 65 ms 66 ms 110 ms N2 180 ms 190 ms 169 ms 123 ms 134 ms 169 ms P2 260 ms 259 ms 252 ms 259 ms 246 ms 290 ms Amplitude Amplitude Amplitude Amplitude Amplitude Amplitude |P1-N2| 3.2 μV 3.23 μV 4.68 μV 1.3 μV 1.08 μV 1.3 μV |P2-N2| 2.89 μV 2.82 μV 5.08 μV 2.33 μV 2.8 μV 2.79 μV Values are shown for self-motion onset and offset. Conventions as in Table 2.
Self-motion onset: O cluster Self-motion offset: O cluster Active Replay Passive Active Replay Passive Latency Latency Latency Latency Latency Latency P1 111 ms 114 ms 96 ms 54 ms 66 ms 104 ms N2 188 ms 191 ms 171 ms 122 ms 135 ms 169 ms P2 240 ms 248 ms 262 ms 246 ms 232 ms 253 ms Amplitude Amplitude Amplitude Amplitude Amplitude Amplitude |P1-N2| 3.58 μV 3.13 μV 5.39 μV 1.8 μV 1.62 μV 1.96 μV |P2-N2| 2.34 μV 1.85 μV 4.76 μV 3.03 μV 2.76 μV 2.67 μV Values are shown for self-motion onset and offset. Conventions as in Table 2.
- Table 5
Results of paired two-tailed t tests for the comparisons between amplitude differences (|P1-N2|, |P2-N2|) and between latencies (P2) for data recorded on the F cluster electrodes
Self-motion onset: F cluster Amplitude differences Latencies |P1-N2| |P2-N2| P2 Active Replay Active Replay Replay Passive t(14) = −3.74 p = 0.002 Not significant t(14) = −3.94 p = 0.001 t(14) = 3.21 p = 0.006 t(14) = −4.4 p < 0.001 Active - Not significant - Not significant t(14) = −3.5 p = 0.004 Amplitude differences |P1-N2| and |P2-N2| were significantly larger in the passive as compared with the active condition and for |P2-N2| also larger compared with the replay condition. In addition, the P2 component had shorter latencies in the active and passive condition compared with the replay condition.
- Table 6
Results of paired two-tailed t tests for the comparisons between amplitude differences (|P1-N2|, |P2-N2|) and between latencies (P1) for data recorded at the C cluster electrodes
Self-motion onset: C cluster Amplitudes Latencies |P1-N2| |P2-N2| P1 Active Replay Active Replay Active Replay Passive t(14) = −3.25
p = 0.006Not significant t(14) = −4.4
p < 0.001t(14) = 4.32
p < 0.001t(14) = −3.79
p = 0.002t(14) = −4.03
p = 0.001Amplitude differences |P1-N2| and |P2-N2| were significantly larger in the passive as compared with the active condition and for |P2-N2| also larger compared with the replay conditions. In addition, the P1 component had shorter latencies in the passive condition compared with the active and replay conditions.
- Table 7
Results of paired two-tailed t tests for the comparisons between amplitude differences (|P1-N2|, |P2-N2|) and between latencies (P1)
Self-motion onset: P cluster Amplitudes Latencies |P1-N2| |P2-N2| P1 Active Replay Active Replay Active Passive t(14) = −4.94 p < 0.001 t(14) = 5.84 p < 0.001 t(14) = −7.71 p < 0.001 t(14) = 7.58 p < 0.001 t(14) = 3.46 p = 0.004 Amplitude differences |P1-N2| and |P2-N2| were significantly larger in the passive as compared with the active and replay conditions. In addition, the P1 components had longer latencies in the active condition compared with the passive condition; p-values were not different for the active versus replay comparison.
- Table 8
Results of paired two-tailed t tests for the comparisons between amplitude differences (|P1-N2|, |P2-N2|) and between latencies (N2)
Self-motion onset: O cluster Amplitudes Latencies |P1-N2| |P2-N2| N2 Active Replay Active Replay Active Passive t(14) = −5.27 p < 0.001 t(14) = 5.92 p < 0.001 t(14) = −4.53 p < 0.001 t(14) = 4.33 p < 0.001 t(14) = 6.28 p < 0.001 Amplitude differences |P1-N2| and |P2-N2| were significantly larger in the passive as compared with the active and replay condition. In addition, the N2 component had longer latencies in the active condition compared with the passive condition; p-values were not different for the active versus replay comparison.
- Table 9
Results of paired two-tailed t tests for the comparisons between latencies (P1, N2, P2)
Self-motion offset: P cluster Latencies P1 N2 P2 Active Replay Active Replay Active Replay Passive t(14) = −18.05
p < 0.001t(14) = 8.05
p < 0.001t(14) = −5.29
p < 0.001t(14) = 6.14
p < 0.001t(14) = −4.36
p < 0.001t(14) = 3.72
p = 0.002The VEP components had longer latencies in the passive condition compared with the active and replay conditions; p-values were not different for the active versus replay comparison.
- Table 10
Results of paired two-tailed t tests for the comparisons between latencies (P1, N2, P2)
Self-motion offset: O cluster Latencies P1 N2 P2 Active Replay Active Replay Replay Passive t(14) = −11.88 p < 0.001 t(14) = 8.64 p < 0.001 t(14) = −10.37 p < 0.001 t(14) = 4.11 p < 0.001 t(14) = 3.67 p = 0.003 The VEP components had longer latencies in the passive condition compared with the active and replay conditions; p-values were not different for the active versus replay comparison.
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