Biology subjects

Fischer Ehmsen, J.

Publications and source records attributed to Fischer Ehmsen, J..

5 recordsLinked to original sources

bioRxiv2025

Hierarchical Bayesian Modelling of Interoceptive Psychophysics

Interoception, the capacity to sense, perceive, and metacognitively appraise viscerosensory and homeostatic signals, is a growing focus in psychology and psychiatry. Adaptive psychophysical tasks now allow quantification of perceptual sensitivity, bias, and precision in cardiac and respiratory domains. However, accurately estimating these parameters often requires large numbers of trials or participants, posing practical challenges, especially in clinical research where participant availability and tolerance are limited. One approach to reduce participant burden while maintaining statistical rigour is to optimise data analysis. Here, we present hierarchical Bayesian models tailored for cardiac and respiratory interoceptive psychophysics that efficiently estimate sensitivity, bias, and precision at both individual and group levels. Using simulations and empirical data, we validate these models and demonstrate that they allow enhanced inference relative to conventional approaches. To support adoption, we provide openly-accessible resources, including a tutorial on how to implement and fit these models in R (written with researchers without modelling expertise in mind) and an app for sample-size justification. These tools facilitate robust, efficient, and generalisable modelling of interoceptive performance, enabling rigorous studies even with limited trials or participant availability.

neuroscience↗

bioRxiv2025

Peripheral Beta-Blockade Differentially Enhances Cardiac and Respiratory Interoception

Interoception, the perception of internal visceral states, arises from complex brain-body interactions across the central and peripheral nervous systems. Despite noradrenalines key role in these interactions, its specific contribution to interoceptive processes remains unclear. In a placebo-controlled, randomised, within-subject study, we employed computational modelling of interoceptive psychophysics to determine how pharmacological beta-adrenoceptor antagonism controls interoception across cardiac and respiratory domains. Both cardio-selective bisoprolol and non-selective propranolol improved cardiac perceptual sensitivity, with bisoprolol exerting an enhanced effect on cardiac metacognition. In contrast, both beta-blockers increased respiratory perceptual precision, with no corresponding changes in sensitivity or metacognition. These findings reveal a novel dissociation between central and peripheral beta-adrenergic mechanisms in interoception, highlighting the pivotal role of peripheral noradrenaline in regulating multi-organ brain-body interactions. Our results suggest that beta-blockers may provide promising routes for modulating distinct facets of interoception, potentially opening new avenues for intervention in conditions characterised by disrupted bodily self-awareness.

neuroscience↗

bioRxiv2024

Microstructural Brain Correlates of Inter-individual Differences in Respiratory Interoception

Interoception, the perception and integration of physiological signals, is a fundamental aspect of self-awareness and homeostasis. While previous work has explored interoceptive processing in relation to the cardiac system, research in the respiratory domain, particularly in relation to brain structure and function, is limited. To address this gap, we utilised a Bayesian psychophysical model to quantify perceptual, metacognitive, and affective dimensions of respiratory interoception in a sample of 207 healthy participants. We also measured individual whole-brain microstructural indices of myelination, myeloarchitecture, and cortical iron using quantitative brain imaging. Voxel-based quantification analyses revealed distinct patterns of cortical microstructure in the insular, cingulate, and primary sensory cortices, which underpin interoceptive perceptual sensitivity and precision. In addition, metacognitive bias was associated with increased myelination of the cingulate cortex and periaqueductal grey, while metacognitive sensitivity correlated with myelination of the midline prefrontal cortex. At an affective level, sensitivity to respiratory resistance was related to the myelination of the primary somatosensory cortex. By revealing specific histological brain patterns tied to individual differences in respiratory interoception, our results uncover the neural pathways that govern perceptual, metacognitive, and emotional facets of interoceptive processing.

neuroscience↗

bioRxiv2023

Disentangling the spinal mechanisms of illusory heat and burning sensations in the Thermal Grill Illusion

The Thermal Grill Illusion (TGI), a phenomenon in which the juxtaposition of innocuous warm and cold temperatures on the skin elicits a burning sensation, offers a unique perspective to how pain occurs in response to harmless stimuli. We investigated the role of the spinal cord in the generation of the TGI across two experiments (total n = 80). We applied heat and cold stimuli to dermatomes, areas of skin innervated by a single spinal nerve, that mapped onto adjacent or nonadjacent spinal segments. Enhanced warm and burning ratings during the TGI were observed when cold and warm stimuli were confined within the same dermatome. Further, we found the spatial organisation of warm and cold stimuli within and across dermatomes affected TGI perception. Perceived warmth and burning intensity increased when the cold stimulus projected to the segment more caudal to the warm stimulus, whilst perceived cold during the TGI decreased, compared to the opposite spatial arrangement. This suggests the perception of TGI is enhanced when cold afferents are projected to spinal segments positioned caudally in relation to those receiving warm afferents. Our results indicate distinct interaction of sensory pathways based on the segmental arrangement of afferent fibres and are consistent with current interpretations of the spread and integration of thermosensory information along the spinal cord.

neuroscience↗

bioRxiv2023

Temporal Contrast Enhancement in Thermosensation: A Framework for Understanding Paradoxical Heat Sensation

Paradoxical Heat Sensation (PHS) is the remarkable feeling of warmth or heat pain while the skin is cooling. Despite its initial documentation over 100 years ago, a unified explanation for this perplexing experience remains elusive. Here we apply contrast enhancement principles, known for their instrumental role in understanding visual illusions, to the domain of thermosensation. Contrast enhancement describes the amplification of two contrasting visual features, such as the enhanced perception of an edge between a light and dark bar. In thermosensation, this encompasses an enhancement of the difference between sequential warming and cooling of the skin, and is defined as the normalised difference between successive temporal warm and cold temperatures. Remarkably, thermal contrast predicts the occurrence of PHS. Our findings reveal compelling evidence supporting the role of thermal contrast in the generation of PHS, shedding light on its underlying mechanism and offering a framework for broader encoding principles in thermosensation and pain.

neuroscience↗