Impairments in interoception (interpreting internal stimuli from within the body) and exteroception (interpreting external stimuli) are characteristic of many mental health disorders, including anxiety. Although there is a growing body of interoceptive research focussed on anxiety, a key challenge is accounting for the inherent physiological variability associated with interoceptive stimuli. Therefore, the primary aim of this project was to develop an analysis protocol to capture measures of interoceptive sensitivity more accurately in the breathing domain, by better ac- counting for physiological variability. Additionally, despite the prevalence of anxiety and common use of selective serotonin reuptake inhibitors (SSRIs) as a pharmacological treatment in Aotearoa New Zealand, little is known about the impact of SSRIs on perceptual processing. While this treatment can be a key step in therapeutic intervention plans, it is important to understand what changes these therapeutic interventions can evoke, who they work best for and in what contexts. Therefore, this project also aimed to explore the effects of SSRIs on interoceptive and exteroceptive perception in individuals who have a clinical diagnosis of anxiety.

Using preliminary data from an ongoing longitudinal study, we firstly developed an analysis protocol to robustly estimate comparable perceptual sensitivity measures in both the interoceptive and exteroceptive domains. This extends on previous interoceptive breathing protocols by capturing and accounting for inherent intra- and inter-participant physiological variability, and standardises these measures for cross-modal comparisons. The preliminary data was then used to assess how six or more weeks of prescribed SSRI treatment influenced three dimensions of breathing-related interoception and visual-related exteroception. Twenty-seven participants completed anxiety and depression questionnaires, a respiratory resistance sensitivity task (RRST; Nikolova et al., 2021), and a visual perceptual task (VPT; Rouault et al., 2019). These allowed us to quantify changes in anxiety and depression symptoms, as well as changes in perceptual sensitivity, confidence, and insight in each interoceptive and exteroceptive domain. Prior to treatment, participants had vastly greater sensitivity to visual stimuli compared to breathing stimuli, while greater confidence and insight were apparent for breathing compared to visual perceptions. Following treatment, alongside the expected (and marked) decreases in the severity of clinical depression and anxiety symptoms, participants also demonstrated improved perceptual sensitivity in both the interoceptive and exteroceptive domains. While confidence improvements approached significance, insight did not improve following treatment. While these results are preliminary in nature, a final analysis using the protocols established here will be conducted on a larger sample size upon completion of the wider study, and will also include an additional control group who are stable on SSRIs to help manage their anxiety symptoms.