Available Tasks#
Breath Hold task#
This task was programmed and presented in Unity. The participant was asked to switch between interleaved periods of holding their breath and periods of paced breathing. During each paced breathing block (30 sec) a bright green circle on a black background repeatedly expanded and contracted at a fixed pace (6 sec per cycle), and the participant was instructed to use this animation to guide their inhalation and exhalation respectively (5 breathing cycles were repeated in each block). At the end of paced breathing blocks the circle changed to yellow, signaling to the participant that this would be their final exhalation and the breath hold period would occur next. During each breath hold block (20 sec) the fully contracted yellow circle remained on the screen, above which the words “Hold your breath!” were displayed. Below the yellow circle a countdown to zero indicating the time left in the block was displayed. When the countdown timer hit zero, the circle turned back to bright green and paced breathing immediately commenced. This was repeated such that the participant completed a total of 6 breath hold blocks and 6 paced breathing blocks.
Passive Auditory task#
This task was programmed and presented in Unity. The task had a block design with two block types: story blocks (n=8) during which the participant listened to short clips from TED talks; and noise blocks (n=7) during which the participant listened to brown noise. After an initial 10s rest period, the story and noise blocks (each lasting for 20s) were presented (via earbuds) in a preset pseudo-randomized order (Fig. 6B). The participant was asked to keep their eyes open and look at a white fixation cross that was presented on a black background throughout the task.
Finger Tapping task#
This task was programmed and presented in Unity. In this task the participant was asked to sit in a chair with their arms on the armrests such that their palms faced upwards, while audio and visual stimuli guided them through randomized periods of left and right–hand finger tapping (n = 10 blocks per side; Fig. 6E). Specifically, at the start of each block the participant was cued in two ways: 1) audibly – brown noise was played through earbuds to either the right or left ear indicating the hand that should be used during the task, and 2) visually – a white image of a hand was displayed on a black screen with either an “L” or an “R” inscribed on it, again indicating the left or right hand should be used. Both cues persisted throughout the block (17.3 sec). Within each block the participant was asked to repeatedly tap the thumb of the cued hand to a certain finger on the same hand. A red dot overlaid on a finger of the visual stimulus indicated which finger to tap. Throughout a block the red dot moved sequentially through each of the four fingers, and each shift to a new finger indicated a new trial (n = 13 trials per block; trial duration = 0.75 sec and inter-trial interval = 0.50 sec). A brief resting period (20 sec) with a white fixation cross on a black screen followed each block.
Go/No-Go task paradigm#
The task, designed and presented using Unity game engine, consisted of two block types: go-only and go/no-go. The overall structure of the task was similar to the one used in a prior publication38. Briefly, participants completed a total of 10 blocks alternating between go-only (n = 5) and go/no-go (n = 5) with each block consisting of 24 trials. Stimuli were green leaf cartoon images (for go trials) and red flower images (for no-go trials) that were presented in a pseudorandom order, which was pre-set and unique for each run. During go/no-go blocks, 30% of the trials were chosen to be no-go trials. A different run of the task was presented at each study visit, however, all participants completed the same versions in the same order.
The task included a 15 s rest at the beginning and a 20 s rest at the end. The task also included a screen to remind the participant of task instructions (e.g. pressing the spacebar when seeing a green leaf and refraining from pressing when seeing a red flower) prior to each block. Stimulus presentation time was 400 ms followed by a 600 ms ± 100 ms inter-trial interval during which only the background was displayed. Participants were asked to provide a response within the 400 ms presentation period. A pleasant (ding) or unpleasant (buzzer) tone, played immediately after participants’ response, was used to provide positive (for hits) and negative feedback (for false-alarms), respectively. The overall task duration was approximately 7 min (Fig. 1c).