On the construct validity of interoceptive accuracy based on heartbeat counting: cardiovascular determinants of absolute and tilt-induced change scores

Interoceptive accuracy (IAcc) as assessed with the heartbeat counting task
(IAccHBCT) may be affected by a range of factors including (1.) the ability to
adequately detect cardiac signals, indicated by IAcc in a heartbeat discrimination task
(IAccHBDT), (2.) cardiac signal properties, affected by sympathetic and
parasympathetic tone, and (3.) non-interoceptive processes, including time estimation
accuracy (TEAcc). In the current study we investigated the contribution of these factors
to absolute and Δ IAccHBCT scores, induced by passive head-up and head-down tilt in
49 healthy individuals. A set of hierarchical regression models showed IAccHBDT
scores as the strongest and, across different orthostatic (tilt) conditions, most stable
(positive) predictor of absolute and Δ IAccHBCT scores. Neither indicators of cardiac
signal properties (except for HR in head-down-tilt), nor TEAcc predicted absolute or Δ
IAccHBCT scores. These findings support the convergent and discriminant validity of
absolute and Δ IAccHBCT scores.