Neural Gating of Bodily Sensations: Relationships with Subjective Perception and Negative Affect
The human central nervous system constantly engages with different stimuli, mostly processed outside of consciousness. Neural gating is the process of filtering out irrelevant/redundant stimuli, and it can be measured by evoking event-related potentials (ERPs) to two identical (paired) stimuli. Reduced auditory gating, i.e. smaller reduction in the ERP amplitude to the redundant sound, has been related to disorders such as schizophrenia, but not much attention has been paid to the neural gating of bodily sensations, e.g. respiratory and somatosensory sensations. While reduced gating of bodily sensations was shown to relate to fibromyalgia and anxiety, it has not yet been related to the subjective perception of aversive bodily events, such as breathlessness or pain – a link potentially relevant for the aversive experience of chronic bodily symptoms. As breathlessness and pain frequently co-occur and share neural networks, investigating both modalities concurrently helps infer if neural gating of bodily sensations arises from a common mechanism. In the first studies of this PhD project, we tested for relationships between neural gating and perception in healthy young adults, using a cross-sectional and a longitudinal (habituation) design. The cross-sectional sample showed a significant relationship of neural gating of respiratory and somatosensory sensations, supporting the idea of a common gating mechanism. No significant correlations emerged between respiratory neural gating and perception, however significant relationships were found for somatosensory gating, with increased perception of aversive sensations relating to better neural gating. Preliminary analyses of the longitudinal data show habituation to respiratory loads, but no relationship of gating to these perceptual changes over time. The second research direction concerns the relationships of negative affect with neural gating and/or perception. A completed study examined the relationships of Error-Related Negativity (ERN) as a neural marker for increased negative affect with the respiratory and somatosensory neural gating. Whereas greater ERN amplitudes related to greater ERP amplitudes for the first stimulus, no correlations emerged with the respective gating, suggesting commonalities between the sensitivity for errors and the neural processing of aversive bodily sensations. One planned study will test for a reduction in respiratory and somatosensory gating by way of unpredictable bodily threat, and another for the moderating effects of symptom-specific fears on the relationships of neural gating and perception. Finally, as there is a lack of studies on improvements in neural gating, the final study will investigate whether transcutaneous vagal nerve stimulation acutely improves respiratory and somatosensory gating. The expected results of this PhD project will improve our understanding of neural mechanisms for increased perception of aversive bodily sensations and potentially contribute to improved treatment options in affected patients.