Fig. 2: Neural recordings, tasks, and behavior.
a We recorded the intracranial activity of the human cortex during fixation, saccadic, and manual responses. b After acquiring a fixation cross, subjects listened to a binaurally presented auditory stimulus. Subjects decided whether they heard more click sounds in the left or right ear. In the congruent task context, subjects (with electrodes implanted in the left hemisphere) made a saccade (SC) to the left side if they heard more clicks on the left, and made a button press (BP) if they heard more clicks on the right. This sensorimotor contingency was flipped in the reversed task context. Subjects were free to indicate their choice following the stimulus onset by making the respective movement. The auditory stimulus ceased upon a choice. A total of 13 sessions were recorded in 8 subjects in the two task contexts (n = 13). Specifically, 7 subjects performed the congruent task, 6 subjects performed the reversed task, and 5 subjects performed both tasks. c Decision variable (DV) computation during an example trial. Red/blue dots indicate auditory clicks in the left/right ears. d DV (mean ± s.d., n = 13) as a function of time, separately for trials that resulted in a SC (red) and BP (blue) choices. One second following the stimulus onset, the DV reached 3.9 ± 2.4 and −3.4 ± 1.8 (mean ± s.d., n = 13) for SC and BP choices, respectively. e Proportion (mean ± s.e.m., n = 13) of SC choices as a function of the DV at the time of choice. The psychometric curve fitting the data of each subject explained 92.4 ± 3.2 % of the variance in the choice behavior (mean ± s.d., n = 13). f Reaction time (mean ± s.e.m., n = 13) as a function of the absolute value of the DV slope for SC (red) and BP (blue) choices. The slope of this relationship was −7.4 ± 6.8 and −10.5 ± 8.5 (mean ± s.d., n = 13) for SC and BP choices, respectively. g, h Eye gaze and hand EMG signals (mean ± s.d.) for trials that resulted in a SC (red) and BP (blue) choices, respectively. Around the time of the choice, the separation, measured by Cohen’s d, was 10.5 ± 3.3 and 3.0 ± 0.7 (mean ± s.d., n = 13) for the eye gaze and EMG signals, respectively.
