The goal of this crossover study was to learn about the potential regulatory role of serotonin in interoceptive processing and its relationship to levels of state anxiety. This experiment directly compared the impact of a selective serotonin reuptake inhibitor (SSRI) (20mg CITALOPRAM) to that of a PLACEBO on the neural processing of ordinary interoceptive sensations and the relationship of these influences to anxious states. Healthy young volunteers completed the visceral interoceptive attention task with each treatment condition (citalopram and placebo). The task involves focusing attention on heart, stomach, or visual sensation control while scanned with functional magnetic resonance imaging (fMRI). The difference in haemodynamic response between interoceptive sensation(s) and visual sensation (i.e. the relative interoceptive response) is compared between treatment conditions. State anxiety is measured at each test period. It is used to test for a moderating effect of state anxiety on the influence of serotonin in interoceptive processing and used post-hoc to explore associations between changes in state anxiety and changes of interoceptive relative interoceptive response due to the SSRI.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
QUADRUPLE
Enrollment
31
Doses were delivered in gelatine capsules filled with microcrystalline cellulose.
Doses were gelatine capsules filled with microcrystalline cellulose
School of Psychology
Falmer, East Sussex, United Kingdom
relative neural interoceptive response - heart
Neural response, inferred via functional magnetic resonance imaging from focusing attention on the heart, minus the response during focus on a visual stimulus
Time frame: 15 minutes
relative neural interoceptive response - stomach
Neural response, inferred via functional magnetic resonance imaging from focusing attention on the stomach, minus the response during focus on a visual stimulus
Time frame: 15 minutes
State Anxiety
State Trait Anxiety Inventory
Time frame: 5 minutes
Metacognitive Interoceptive Insight
Ability of confidence to predict accuracy when making decisions about whether heartbeat is in sync with an auditory tone. This is an exploratory measure.
Time frame: 45 minutes
Physiological and Psychological state
Three scales (from 0-100) were given to assess three somatic side effects (nausea, headache and dizziness). Five anxiety-related effects (pairs of antonyms: alert-drowsy, stimulated-sedated, restless-peaceful, irritable-good-humoured, anxious-calm) were used to confirm other anxiety measures and alert the researchers to excessive side effects. Used to confirm anxiety measure detect side effects.
Time frame: Measured twice, for 2 minutes, before and after scanning. Average taken to estimate state inside scanner.
Positive and Negative Affect Scale
Measures affective state, confirming anxiety measure
Time frame: Measured twice, for 2 minutes, before and after scanning. Average taken to estimate state inside scanner.
Heartrate
Participants had their heartrate recorded with the participant relaxed and sitting.
Time frame: Before scans of each session, 2 minutes
Cerebral Blood Flow Change
Perfusion imaging, to control for effects of citalopram on blood flow
Time frame: 2 minutes, at scan
Anatomical scan and fieldmaps
For coregistration of functional magnetic resonance images
Time frame: 6 minutes, at scan
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