Prismatic Adaptation Induces Plastic Changes onto Spatial and Temporal Domains in Near and Far Space

Abstract

A large literature has documented interactions between space and time suggesting that the two experiential domains may share a common format in a generalized magnitude system (ATOM theory). To further explore this hypothesis, here we measured the extent to which time and space are sensitive to the same sensorimotor plasticity processes, as induced by classical prismatic adaptation procedures (PA). We also exanimated whether spatial-attention shifts on time and space processing, produced through PA, extend to stimuli presented beyond the immediate near space. Results indicated that PA affected both temporal and spatial representations not only in the near space (i.e., the region within which the adaptation occurred), but also in the far space. In addition, both rightward and leftward PA directions caused opposite and symmetrical modulations on time processing, whereas only leftward PA biased space processing rightward. We discuss these findings within the ATOM framework and models that account for PA effects on space and time processing. We propose that the differential and asymmetrical effects following PA may suggest that temporal and spatial representations are not perfectly aligned.

Figures

Figure 1

Graphical representation of sequence of events in each trial for the two tasks. (a) Landmark task. Following 750 ms presentation of a blank, pretransected lines were presented for 2000 ms before reappearance of the blank on the screen until the subject responded. Lines were pretransected at 1 of 11 locations ranging symmetrically from −0.5° to +0.5° of visual angle (distance between transector locations = 0.1°) and including veridical center. After the participant's response (the transector is closer to the “right” or to the “left”), a black-and-white patterned mask was presented at random duration (range 500–1500 ms) before the next trial was presented. (b) Time bisection task. Following 750 ms presentation of a blank, pretransected lines were presented before reappearance of the blank until the subject responded. Lines were pretransected at veridical center and had 1 of 11 different duration ranging from 1000 to 3000 ms at 200 ms intervals. After the participant's response (the duration of the line is “short” or “long”), a black-and-white patterned mask was presented for a random duration (range 500–1500 ms) before the next trial.

Figure 2

Point of subjective equality judgments (PSE) as a function of prism group (LPA and RPA) and session before (dark gray) and after PA (light gray). Landmark task (a): the line transector is judged (in visual angle) as nearer to the left (negative values) or to the right (positive values). After LPA the line transector is judged as nearer to the right compared to before PA (positive values). Time bisection task (b): interval duration (in millisecond) is classified as short (2000 ms). After LPA the time interval is classified as longer compared to before, whereas after RPA the time interval is classified as shorter compared to before PA. Bars represent the average point of subjective equality for spatial and temporal judgments, respectively, ± standard error (SEM). ∗p < .05.

Figure 3

Theoretical model of the plastic prismatic adaptation effects on spatial representation of time processing. (a) The horizontal black line represents a putative duration to be bisected. The central vertical marker represents the real midpoint of the temporal duration. The little vertical lines represent time beats indicating the velocity of time flow passage: the greater the distance between the lines, the slower the passage of time flow. (b) The horizontal dark gray line represents time duration perceived by participants before PA. The central vertical marker represents the temporal bisection judgment of participants before PA. The real time duration and the perceived duration by participants are aligned: the passage of time flow of the perceived duration has the same velocity of the real duration. (c) Leftward shift of spatial attention following RPA induces an underestimation of time. The horizontal dashed black arrow represents the leftward shift of spatial attention induced by RPA. The horizontal light gray line represents the time duration perceived by participants after RPA. The central vertical marker represents the temporal bisection judgment of participants after RPA. The real time interval and the perceived interval are not aligned because of the rightward bias of spatial attention: the passage of time flow of the perceived duration beats more slowly than the real duration. (d) Rightward shift of spatial attention following LPA induces an overestimation of time. The horizontal dashed black arrow represents the leftward shift of spatial attention induced by LPA. The horizontal light gray line represents the time duration perceived by participants after LPA. The central vertical marker represents the temporal bisection judgment of participants after LPA. The real time interval and the perceived interval are not aligned because of the rightward bias of spatial attention: the passage of time flow of the perceived duration beats more quickly than the real duration.