Figure 2.

Behavioral protocol and results for all patients. a, Schematic of the 2AFC detection procedure. Participants fixate on a central cross, with the onset of each 1500 ms interval alerted by a low (interval 1) or high (interval 2) pitch tone. The stimulus can appear in either interval, for a period of 500 ms. At the end of the trial, participants are instructed to decide which interval the stimulus appeared, with a subset of patients also asked to rate the confidence of this response. b, Throughout the experiment, fixation was recorded with eye tracking. Example data over three trials are displayed here, with the y-axis representing horizontal gaze position on the screen (amplitude bar for scale). Any trials containing eye movements >1° toward the stimulus were excluded from analysis (red top plot); blue plots (bottom) represent adequate fixation. c, Individual 2AFC detection performance for all individuals. The individual at chance (P3, dotted line) is clearly distinct from other patients. When patients demonstrate identical scores for the same contrast levels, overlapping data points are plotted immediately above and/or below for visualization purposes. d, Average group performance; error bars represent SEM. Detection exhibits a logarithmic relationship with contrast (R² = 0.98). e, Individual confidence ratings were collected in four patients, plotted here against detection performance. The relationship is described by a nonlinear curve, with confidence increasing the most for higher performance scores (R² = 0.89; MSE, 1.3).