Abstract
Research on how humans perceive sensory inputs from their bodies (“interoception”) has been rapidly gaining momentum, with interest across a host of disciplines from physiology through to psychiatry. However, studying interoceptive processes is not without significant challenges, and many methods utilized to access internal states have been largely devoted to capturing and relating naturally occurring variations in interoceptive signals (such as heartbeats) to measures of how the brain processes these signals. An alternative procedure involves the controlled perturbation of specific interoceptive axes. This is challenging because it requires non-invasive interventions that can be repeated many times within a subject and that are potent but safe. Here we present an effective methodology for instigating these perturbations within the breathing domain. We describe a custom-built circuitry that is capable of delivering inspiratory resistive loads automatically and precisely. Importantly, our approach is compatible with magnetic resonance imaging (MRI) environments, allowing for the administration of complicated experimental designs in neuroimaging as increasingly required within developing fields such as computational psychiatry/psychosomatics. We describe the experimental setup for both the control and monitoring of the inspiratory resistive loads, and demonstrate its possible utilities within different study designs. This methodology represents an important step forward from the previously utilized, manually controlled resistive loading setups, which present significant experimental burdens with prolonged and/or complicated sequences of breathing stimuli.
Highlights
A fundamental aspect of complex beings is the sensation, perception, and control of the physical body
Active perturbations of bodily states are important for clinical applications (Stewart et al, 2014; Berner et al, 2017), not least in computational psychiatry/psychosomatics where model-based assessment of interoceptive surprise in individual patients plays a central role in proposals for differential diagnostics (Stephan et al, 2016; Petzschner et al, 2017)
The relationship between the inspiratory pressure generated in each stimulus and the remaining physiological measures is demonstrated in Figure 4, whereby no significant associations were observed between inspiratory pressure and breathing rate, depth, PETCO2 nor PETO2 for this example participant
Summary
A fundamental aspect of complex beings is the sensation, perception, and control of the physical body. We can consider actively invoking changes in these systems in a controlled, timely and reversible manner Such active disturbances are critical for testing hypotheses about the principles that govern interoception. A critical prediction of these theories concerns the occurrence of specific prediction error signals (interoceptive surprise), e.g., reflected by activity of the insula, in response to unexpected changes in sensory inputs from the body. Testing this prediction requires experimental perturbations that elicit controlled prediction errors in a trial-by-trial fashion. Active perturbations of bodily states are important for clinical applications (Stewart et al, 2014; Berner et al, 2017), not least in computational psychiatry/psychosomatics where model-based assessment of interoceptive surprise in individual patients plays a central role in proposals for differential diagnostics (Stephan et al, 2016; Petzschner et al, 2017)
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