Design, predictions, and stimuli. A, Tested positions (left, right, top, and bottom) for the width and height judgment tasks. B, Predicted elongation for the deprived condition. If deprived cortex representing the BS starts to respond to stimuli outside the BS, stimuli might be perceived as extending into the BS. C, Stimuli used for the width judgment task. Five rectangles with identical height (2°), but varying in width (1.5, 1.75, 2, 2.25, and 2.5°), were presented one at a time in each of the four locations. In the height judgment task, the rectangles were rotated 90° (not pictured).
Perceptual elongations after 10 min and 2 h of deprivation. The figure depicts the mean elongation judgment along the axis of predicted distortion (i.e., the horizontal axis for stimuli presented to the left and right of the BS; the vertical axis for stimuli presented above and below the BS), as a function of stimulus aspect ratio (see black and gray rectangles). The black lines show the undeprived conditions (solid black line, right eye was patched; dashed black line, neither eye patched, i.e., binocular viewing). The blue and green lines show the deprived conditions at 2 h and 10 min, respectively. In the undeprived control conditions, a square (x-axis: 0% difference in width and height) is perceived veridically (y-axis: 0 elongation judgment or square). In the deprived condition, this same stimulus is seen as elongated along the predicted axis of distortion (i.e., wider when presented to the left and right of the BS, and taller when presented to above and below the BS). More generally, the upward shift of the curves in the deprived conditions (blue and green lines) indicates an elongation of all rectangles along the axis of predicted distortion after 2 h of deprivation and after 10 min. The PSE indicates the rectangles that were perceived as squares after deprivation (shown in red): the PSE was −9%, which indicates that a rectangle either 9% thinner than a square (if presented to the left and right of the BS) or 9% shorter than a square (if presented above and below the BS) was perceived as a square. The 9% magnitude of elongation was significantly different from 0 (in which 0 indicates no distortion and was outside the 95% confidence interval around the PSE) after both 10 min and 2 h of deprivation, and the magnitude of the effect did not differ in the two cases (t(9) = 0.35; p = 0.73). Moreover, the effect was significantly greater after each deprived condition than in each undeprived control condition (t(9) = 4.54, 3.36 for 10 min vs binocular and monocular controls, respectively, and 6.24, 4.81 for 2 h vs binocular and monocular controls, respectively; all 4 p values <0.01). No significant elongation was found in either of the undeprived control conditions (the 95% confidence interval around the PSE for each condition included 0), nor did the two conditions differ from each other (t(9) = 0.51; p = 0.62).
Time course of elongations over 8 min of deprivation. The graph depicts the PSEs (indicating the size rectangle perceived as square) for the deprived (gray bars) and undeprived (black bars) conditions across 2 min time intervals. Error bars reflect the 95% confidence intervals around the PSE. Within 2 min, rectangles presented next to the deprived BS had to be elongated by nearly 8% to be perceived as squares. In the deprived condition, the magnitude of elongation at all time intervals was significantly >0 (the 95% confidence interval around the PSEs did not include 0), and they did not differ from each other (F(3,57) = 0.164; p > 0.9). In contrast, no significant elongation was found at any of the four time points in the undeprived condition (the 95% confidence intervals included 0), nor did they differ from each other (F(3,57) = 1.35; p > 0.25).
Second-by-second analysis of perceptual elongations. The figure depicts the PSEs (indicating the size rectangle perceived as square) for every trial over a 2 min block for the deprived (red line) and undeprived (black line) conditions. Each trial took ∼1 s. The shaded area around each curve indicates the 95% confidence interval around that PSE. On the very first trial (i.e., within the first second after the onset of deprivation), significant elongation was observed (PSE of −10%, and the 95% confidence interval did not include 0). In contrast, on the very first trial after the deprivation ends, the elongations reverse and perception returns to normal (PSE of −2%, and the 95% confidence interval includes 0).