Stimulus and behavior timeseries
RVT
CONTRACTION
The three active localizer conditions, Active Exteroception, Active Interoception, and Active Matching required button-presses to track the sensory target, i.e., inhalation/exhalation during the respiratory cycle, or expansion/contraction during the visual circle cycle. Each active condition therefore produced three periodic timeseries: (1) the circle radius, as measured by timestamps in the participant log files, (2) respiration belt amplitude, as measured by pressure transduction on an MR-compatible respiration belt, and (3) a waveform generated from participant button presses, with button presses indicating inflection points (peaks and troughs) of the response waveform.The respiration belt waveform was obtained directly from a physiological logfile for each fMRI run. Respiration data were sampled at 500 Hz and included a scanner-generated timestamp to precisely indicate the beginning and end of the functional run. Respiration data were segmented into task trials using timestamps from participant logfiles. The ‘pracma’ library (Respiration and behavior tracking. Effects of the respiratory volume/time (RVT) covariate on BOLD activity. Contrasts maps were generated from the five-condition model corrected using threshold-free cluster estimation (TFCE) to the familywise Behavioral keypress waveforms were generated using linear interpolation of behavioral logfile timestamps for button presses using the The circle stimulus waveform was obtained from the stimulus presentation software. The circle period was matched to participant-specific breathing frequencies obtained via respiration belt during structural MRI acquisition. For each trial, the timeseries began at an arbitrary unit of 0. The expansion/contraction period was symmetrical and defined as half the participant respiratory period. The circle value was then extrapolated as increasing from −1 for the expansion period to reach a value of 1 by the end of the period; the circle then paused for 0.2 * the expansion period; the circle then decreased at the same rate for the contraction period to reach a value of −1 by the end of the period, and then paused again for 0.2 * the contraction period, repeating the cycle the end of the task block.