Supplementary Materials and Methods s5

SUPPLEMENTARY MATERIALS AND METHODS

Neurocognitive tasks The neurocognitive battery comprised five tests, tapping functions associated with large to medium effect sizes in meta-analyses of neurocognitive performance in ADHD vs. controls and suggested to be in part mediated by catecholamine systems . Descriptions of these tests appear below.

Stop Signal Paradigm The stop signal paradigm assesses inhibitory control by measuring the time required to stop a planned response, i.e. stop signal reaction time (SSRT) . A participant responds rapidly (with a mouse click) to the on-screen presentation of go-signals in a choice reaction time task. On 25% of the trials, a stop-signal (a tone) follows the go- signal, instructing the participant to withhold the response. The success of withholding depends on the timing of the stop signal in relation to the go signal, and on the latency of the inhibitory response relative to the go-response. The delay between the go-signal and the stop-signal was varied with an algorithm that ensured successful inhibition on 50% of Stop trials for each participant. Participants completed eight blocks of 32 trials each, preceded by 2 practice blocks.

Antisaccade The antisaccade task measures inhibitory oculomotor control . It requires the participant to inhibit a reflexive saccade to a suddenly appearing peripheral target and, instead, generate a saccade to its mirror location in the opposite hemifield (i.e. an antisaccade). A reflexive saccade towards the target (an antisaccade error) is the measure of inhibitory failure. The control condition for the antisaccades is the prosaccade task, where participants make visually guided saccades to the target. Participants completed two prosaccade (PS) and two antisaccade (AS) blocks of 30 trials each, preceded by one practice block of each task. Blocks were presented in palindromic order (PS-AS-AS-PS, or AS-PS-PS-AS), counterbalanced across participants in each group. Stimuli were identical for prosaccades and antisaccades; only the instructions differed. Each trial began with a central fixation target (a red square subtending 0.5° x 0.5° of visual angle) presented for a period of 1 to 2 seconds (generated randomly for each trial). The offset of the central fixation coincided with the presentation of an identical peripheral target at 12° left or right of center (direction pseudo-randomized across trials within each block), which remained on for 1000 ms. Participants were seated 57 cm from a 17-inch View Sonic LCD monitor running at 135 Hz, onto which the stimuli were presented. Eye movements were monitored using the Eye link II high-speed (500 Hz) infrared pupil tracker (SR Research, Osgood, ON). Recordings were made from the dominant eye. Prior to each block, a three-point calibration was performed and between trials, a drift correction. Two measures of inhibitory function were analyzed from the antisaccade task: error rate, which reflects a failure to inhibit a prepotent oculomotor response, and the rate of anticipatory saccades (latency ≤ 80ms), which reflects impulsive responding when waiting for the peripheral target to appear. Go/No-Go discrimination learning The computerized Go/No-Go Discrimination learning task measures the effects of reward and punishment on the likelihood of responding and withholding responses. In each of the task’s 4 conditions, participants were presented with eight two-digit numbers in random order over 80 trials. Half of these numbers were “active” stimuli requiring a mouse click, while the other half were “passive” stimuli requiring a non-response. Participants were not informed which stimuli were “active” and which were “passive”, but learned through feedback by trial and error. The four conditions, with different sets of stimuli in each, differed in the feedback provided. In the Reward-Punishment (Active Feedback) condition, only active responses (mouse clicks) received feedback: correct mouse clicks to active stimuli were rewarded (win 10 cents), and incorrect mouse clicks to passive stimuli (commission errors) were punished (lose 10 cents). Feedback was not provided when an active response was withheld. In the Reward-Reward (Correct Feedback) condition, rewards were provided for correct responses to active stimuli and correct non-responses to passive stimuli; there was no punishment. In the Punishment- Punishment condition (Incorrect Feedback), subjects were punished when they incorrectly withheld a response to an active stimulus and responded to a passive stimulus; correct responses were not rewarded, so participants could only lose money. Finally, in the Punishment-Reward condition (Passive Feedback), participants received feedback only on trials where they withheld responses. They were rewarded for correctly withholding a response and punished for incorrectly withholding one; no feedback was provided after making an active response. Each condition included a “pretreatment” learning phase of 12 unscored trials.

Self-Ordered Working Memory Tasks These computerized adaptations of the Self-Ordered Pointing Tasks measured planning and monitoring aspects of working memory. Participants were presented with 12 consecutive arrays of the same 12 stimuli, but the position of each stimulus varied from one array to the next. The task was to select a stimulus in each array that has not yet been selected in any of the previous arrays (each stimulus is to only be selected once). In the “concrete” version of the task the stimuli were easily recognized objects, such as a bus or a light-bulb, whereas in the “abstract” version, the stimuli are abstract images difficult to label with verbal descriptors. To prevent use of a spatial strategy, participants could not select the same stimulus position on consecutive trials.

Trail-Making Test The trail-making test measures cognitive flexibility. It has two components. In part A, participants quickly trace a path connecting a series of consecutive numbers (one to twenty-five) positioned randomly on a page. In part B, participants trace a path alternating between 12 numbers and 12 letters, in the ascending order (i.e. 1, A 2, B etc.). While both A and B tap into spatial scanning and visuomotor speed, part B adds the requirement to rapidly shift mental sets, resulting in longer completion times. Prior to starting the task, the participants were given 8-item practice versions of parts A and B to ensure that they understood the task. Their performance was timed with a stopwatch.

Tower of Hanoi The Tower of Hanoi assesses problem-solving ability and planning . Participants are presented with three equally distanced pegs of the same length. On one of these pegs, five rings are stacked in order of decreasing size. The participant’s task is to transfer this stack to another peg, one ring at a time, in as few moves as possible, and never placing a larger ring on top of a smaller one. The participants completed two 5-ring trials of the computerized version of this task preceded by a 3-ring practice. SUPPLEMENTARY RESULTS

Neurocognitive tasks: The results for the stop signal paradigm and the antisaccade task appear in the main text. For the self-ordered working memory tasks, the trail-making test, or the Tower of Hanoi task, Group was not significant as a main effect or in interaction with other variables. On the Go/No-Go Discrimination learning task, the ADHD group made significantly more errors than controls across all reward and punishment contingencies (Group: F(1,23) = 4.25; p = .05), which cannot be attributed to a specific executive function deficit. Group did not interact significantly with any other factor (all ps > .05) (Table S1). Table S1. Neurocognitive performance of Control and ADHD participants.

Task Controls (n = 12) ADHD (n = 14) p

Go/ No-go Discrimination Learning 8.88 (6.32) 13.64 (5.56) .05 Mean % Total Errors (SD)

Self Ordered Working Memory: Concrete: mean # errors (SD) 1.08 (1.16) 1.14 (1.03) .90 Abstract: # errors (SD) 1.50 (1.16) 2.29 (1.34) .09 Trail Making Test: Trails A: mean completion time, sec (SD) 21.94 (4.41) 25.98 (8.21) .14 Trails B: mean completion time, sec (SD) 47.12 (22.08) 58.83 (22.51) .19 Tower of Hanoi Mean # of moves for 5-ring versions (SD) 78.96 (44.22) 92.25 (49.65) .48

Legend: Neurocognitive performance of Control and ADHD participants Table S2. Significant clusters of d-amph-induced decrease in BPND on t-maps Controls (n = 18) x y z Peak Cluster size t-value (# significant voxels) Ventral Striatum Left -11.4 5.8 -8.1 5.2 210 Right 7.7 15.8 -3.4 5.7 295 Right 10.1 8.8 -9.4 4.2 22 Right 18 9.2 -8.3 3.8 19 Post-commissural Putamen Left -28.3 -10.5 -1.3 4.3 189 Right 30.7 -10.7 -4.4 4.3 280 ADHD (n = 15) Pre-commissural Caudate Left -13.0 15.0 -1.4 4.9 278 Pre-commissural Putamen Left -28.7 0.8 0.4 5.2 284 Right 25.8 6.0 -3.2 5.3 977 Post-commissural Putamen Left -26.9 -4.2 3.4 6.2 1525 Right -28.0 -3.5 1.5 6.5 1383 Ventral Striatum Left -19 6.2 -10.1 3.8 13 Right 11.5 12.0 -8.4 3.8 4 All voxels have t-values ≥ 3.8. Table S3. Blood pressure and heart rate for placebo and d-amph testing sessions.

Baseline Tracer Mid-Scan End of Scan 30 min Post-Scan CONTROLS (n=15) Placebo Systolic BP (SD) 122.85 (7.58) 131.54 (11.35) 122.08 (10.11) 120.92 (11.43) 126.62 (10.53) Diastolic BP (SD) 77.30 (7.95) 77.31 (9.38) 71.92 (6.29)* 73.38 (7.68) 74.85 (7.00) Heart Rate (SD) 64.84 (7.51) 60.00 (6.19) 58.23 (5.61)* 60.00 (8.74) 56.92 (5.20)* d-amph Systolic BP (SD) 122.38 (7.48) 136.15 (11.50)** 136.08(15.33)§§ 147.31 (13.03)**§§ 147.38 (14.84)**§§ Diastolic BP (SD) 73.23 (11.43) 77.23 (10.79) 80.08 (8.57)§§ 84.38 (8.24)§§ 85.31 (8.11)*§§ Heart Rate (SD) 64.54 (11.70) 56.69 (6.59) 60.15 (6.94) 60.38 (7.90) 62.46 (7.74)§ ADHD (n = 15) Placebo Systolic BP (SD) 121.15 (8.88) 130.15 (12.83)* 119.15 (7.85) 121.54 (8.84) 123.69 (9.26) Diastolic BP (SD) 75.85 (7.79) 72.38 (7.14) 68.31 (7.39) 71.84 (5.54) 73.08 (6.47) Heart Rate (SD) 70.46(13.65) 65.85 (11.95) 60.62 (9.10)* 63.62 (11.38)** 62.31 (11.83)** d-amph Systolic BP (SD) 120.00 (8.27) 134.23 (13.40)* 139.69(18.80)*§§ 147.08 (17.13)**§§ 151.23 (20.33)**§§ Diastolic BP (SD) 75.23 (7.43) 76.23 (7.87) 80.00 (9.99)§§ 79.85 (8.95)§§ 82.38 (8.92)§§ Heart Rate (SD) 74.77 (11.92) 68.15 (13.77) 66.92 (13.67)§ 66.15 (12.19) 68.46 (14.78)§

Mean blood pressure (mmHg) and heart rate (beats/ minute) during placebo and d-amph testing sessions. *p <.05 compared to baseline; **p< .01 compared to baseline; §p < .05.significant difference between placebo and d-amph; §§p < .01.on d-amph compared to placebo. There are no significant Group differences or interactions with Group. Table S4: Subjective self-reported effects of d-amph. CONTROLS (n=15) ADHD (n = 15) Area under the curve Placebo d-amph Placebo d-amph

Rush (SD) 386.79 (238.24) 482.50 (203.91)* 385.00 (233.37) 460.17(270.76) High (SD) 311.25 (206.62) 405.00 (193.92)* 380.00 (235.12) 488.17(272.58)* Euphoria (SD) 276.96 (117.59) 358.75 (196.49)* 354.17 (188.14) 428.67 (225.44) Excited (SD) 403.57 (190.59) 468.39 (154.38) 445.50 (221.95) 569.50 (221.05)** Anxious (SD) 314.46 (145.94) 341.07 (163.68) 453.33 (229.11) 425.33 (260.58) Energetic (SD) 476.43 (196.67) 570.54 (121.57)* 539.67 (227.99) 642.67 (187.00)** Drug Liking (SD) 426.96 (251.34) 495.71 (221.56) 410.50 (235.80) 569.83 (248.69)* Mind Racing (SD) 452.86 (257.51) 539.11 (203.91) † 427.00 (222.43) 491.83 (308.56) Alert (SD) 618.04 (200.12) 734.64 (138.40)** 627.00 (221.53) 758.67 (174.45)** Drug Wanting (SD) 430.71 (262.78) 459.11 (270.49) 396.83 (240.03) 555.67 (278.82)* Area under the curve values for subjective effects of placebo and d-amph were calculated based on reports at 6 points throughout the scan (Baseline, entry into the scanner, tracer delivery, mid-scan, end of scan, and immediately post-scan); d-amph vs. placebo: †p < .1, *p <.05, **p< .01. There are no significant Group differences or interactions with Group. REFERENCES:

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