Hypothesis testing
RVT
Hypothesis 1 aimed to compare interoceptive and exteroceptive attention. To this end we first evaluated a whole-brain interaction between reporting demand [active vs passive] and attentional target [interoception vs exteroception] to evaluate whether the effects of attentional target should be evaluated separately for the active and passive reporting conditions. Subsequent analyses compared the simple effects of attentional target within each reporting demand condition, i.e., [Passive Interoception vs Passive Exteroception] and [Active Exteroception vs Active Interoception]. To perform these contrasts, all five task conditions were estimated separately at the first (individual session) level of analysis and entered into a full factorial design in SPM12.Hypothesis 2 aimed to investigate whether the differences between exteroception and interoception were moderated by individual differences in subjective interoceptive awareness (MAIA scores). Focusing on the contrast of [Active Interoception vs Active Exteroception], we first created contrast maps at the first (within session) level of analysis. These first level maps were then entered into a second (group)-level analysis that included normalized (z-scored) MAIA scale total scores as a covariate of interest. The MAIA covariate was subjected to TFCE correction in the same fashion as other whole-brain analyses, and respiration rate and RVT change between the two conditions was included in the factorial model as a nuisance covariate to control for variation associated with physiological changes. Exploratory analyses of each MAIA subfactor are also available as Extended Data Hypothesis three tested the potential moderating factor of endogenous versus exogenous control of the respiratory cycle by contrasting each of Active Exteroception and Active Interoception against Active Matching using the same five condition model from testing Hypothesis 1.Hypothesis four aimed to understand how engaging in Active Interoception changes brain connectivity relative to Active Exteroception. To accomplish this aim, a psychophysiological interaction (PPI) analysis was conducted in SPM12 using the Generalized PPI Toolbox (v. 13.1), which improves on standard PPI analyses by estimating the effect each task condition has on connectivity independently (To define a region of interest (ROI), the conjunction of the [Active Exteroception – Active Interoception] contrast and the positive MAIA contrast was evaluated, using a threshold of 