An Active Inference Approach to Interoceptive Psychopathology

Abstract

Interoception refers to the process by which the nervous system senses and integrates signals originating from within the body, providing a momentary mapping of the body's internal landscape and its relationship to the outside world. Active inference is based on the premise that afferent sensory input to the brain is constantly shaped and modified by prior expectations. In this review we propose that interoceptive psychopathology results from two primary interoceptive dysfunctions: First, individuals have abnormally strong expectations of the situations that elicit bodily change (i.e., hyperprecise priors), and second, they have great difficulty adjusting these expectations when the environment changes (i.e., context rigidity). Here we discuss how these dysfunctions potentially manifest in mental illness and how interventions aimed at altering interoceptive processing can help the brain create a more realistic model of its internal state.

Keywords: anxiety; computational psychiatry; depression; interoception; mental health; predictive coding.

Figure 1

Active inference interoceptive dysfunction 1: hyperprecise priors. This image depicts priors symbolically; the size of the individual symbol is proportional to the degree to which the individual believes this expectation. For example, say a person is walking in the Rocky Mountain forest and is listening for animals known to inhabit the area. Suddenly, they hear a sound (afferent evidence) that is paired with an interoceptive prediction (heartbeat) that is proportional to the expected percept. Soon after, they see the source of the sound, in this case a rabbit. In a typical case (right), if the person expects to encounter a rabbit and a bear with equal frequency (i.e., these competing models have modest precision), then hearing a sound will trigger competing models (bear or rabbit) and elicit preparatory interoceptive responses (e.g., heightened sympathetic tone). If a rabbit subsequently appears, a prediction error ensues that should adjust (increase) the prior expectation of seeing a rabbit when the same sound is heard again (new afferent evidence). The perception of the animal thus creates a prediction error in the presence of the prior expectation and modifies these expectations for the next encounter. In this case, the same sound presented after seeing a rabbit no longer elicits a prediction error. On the other hand (left), if the person is highly convinced to begin with that a bear will come charging out of the woods (i.e., the model is very precise), then even if they hear a rabbit, the expectation of a bear charging out of the woods will continue with little adjustments. Importantly, a prediction error persists over time because the model is not brought into congruence with the evidence.

Figure 2

Active inference interoceptive dysfunction 2: context rigidity. A second form of dysfunction occurs when the individual maintains the same model in a new context. For example, upon emerging from the Rocky Mountain forest into the prairie grasslands of Oklahoma (devoid of bears but with an abundance of rabbits), an individual may still associate the sound of an approaching rabbit with the perception of a charging bear. Whereas an adaptive person initially establishes a new and context-specific model (there may be bears or rabbits in this new environment; right), the nonadaptive person continues to maintain the previously held belief of a high prevalence of bears despite being in a different environment (left).