Biology subjects

Dalmaijer, E. S.

Publications and source records attributed to Dalmaijer, E. S..

6 recordsLinked to original sources

bioRxiv2025

Orthorexia is associated with a paradoxical appetitive gastric response to unhealthy foods

Orthorexia involves an obsessive tendency towards "healthy" foods. It is a risk factor for eating disorders (anorexia nervosa and the proposed "orthorexia nervosa") and psychological distress, but its biological mechanism remains unknown. We hypothesised that this mechanism operates through the stomach: increased gastric power differentiates appetising from unappetising foods, vagal stimulation reduces food liking, and gastric proto-nausea can be evoked by disgust; all contributors to disordered eating. We used electrogastrography alongside high-density facial landmark tracking to gauge responses to minimally processed ("healthy"), highly processed ("unhealthy"), and culturally unaccepted ("disgusting") foods in a non-clinical sample (N=77). Trait orthorexia was associated with increased self-reported desire to eat healthy foods. Moreover, we found that higher orthorexia was associated with increasing disgust-related facial responses to unhealthy and disgusting foods. We then identified a relationship between food-healthiness ratings and gastric power: those who generally assigned lower healthiness ratings to foods showed higher gastric power for unhealthy than healthy foods, whereas those who expressed higher healthiness ratings showed higher gastric power for healthy over unhealthy foods. This suggests that the stomach tracks individual differences in eating preferences. Crucially, and contrary to our expectations, higher trait orthorexia was associated with a paradoxical increase in gastric power to unhealthy foods. One explanation is that higher gastric power for unhealthy foods reflects increased appetite for self-denied foods. Alternatively, orthorexia itself could be an adaptive response to exert stronger cognitive control over a pre-existing gastric appetite for unhealthy foods.

physiology↗

bioRxiv2021

Testing for implicit emotion regulation in childhood

Although implicit emotion regulation is thought to be critical for psychosocial development and mental wellbeing, few studies have investigated the neural underpinnings of this form of emotion regulation in children. We used a modified emotional Go/NoGo block design fMRI task to explore the neural correlates of implicit emotion regulation and individual differences in a sample of 40 children (50% female, mean age = 8.65 {+/-} 0.77). Conditions included happy, sad, neutral, and scrambled faces as implicit distractors within the actual Go/NoGo targets. We used a relatively standard preprocessing pipeline via fMRIprep, with T-contrasts for response inhibition and emotional effects, and a nonparametric multiple comparisons procedure, with SnPM, for our group-level analysis. There were multiple significant response inhibition effects, including larger NoGo vs Go activation in the IFG, insula, and MCC/ACC. Valence effects showed significantly greater right putamen activity for the Sad NoGo vs Go contrast and greater bilateral putamen and right pallidum activity for the Happy Go vs Sad Go contrast. These results provide preliminary findings of neural substrates, particularly the putamen, that may be associated with implicit emotion regulation in children.

neuroscience↗

bioRxiv2020

Twin studies with unmet assumptions are biased towards genetic heritability

For a century [1,2], studies of monozygotic and dizygotic twins have yielded estimates of trait heritability. The clever logic behind them is that while both types of twins share environments, their genetic overlap is different. Hence, larger trait correlations between monozygotic compared to dizygotic twins indicate heritability (nature), whereas similar correlations indicate shared environmental influences (nurture), and low correlations indicate shaping through non-shared environments (external influences and measurement error). While many have written on the assumptions that both types of twins share equal environments [3-5], and that parental genetics and environment are independent [6,7]; fewer have put their data where their mouth is. Here, the impacts of unmet assumptions were investigated using a generative mixture model of twin phenotypes. The results indicated that violations of the equal environments assumption yielded large overestimations of heritability and underestimations of shared environmental influences. On the other hand, when parental genetics shaped twins shared environments, only minor non-linear biases against heritability emerged. Finally, realistic levels of measurement error uniformly depressed estimates for genetic and shared environmental factors. In sum, twin studies are particularly susceptible to overestimation of genetic and non-shared environmental influences. This bias could explain why some traits, such as attitudes towards property taxes [8], show suspiciously high heritability without a biologically plausible mechanism. Particularly in the context of traits with convincing mechanisms of cultural transmission [9-11] and complex gene-environment interactions [6], researchers should not allow biases in twin studies to overestimate heritability.

genetics↗

bioRxiv2018

Parallel encoding of information into visual short-term memory

Humans can temporarily retain information in their highly limited short-term memory. Traditionally, objects are thought to be attentionally selected and committed to short-term memory one-by-one. However, few studies directly test this serial encoding assumption. Here, we demonstrate that information from separate objects can be encoded into short-term memory in parallel. We developed models of serial and parallel encoding that describe probabilities of items being present in short-term memory throughout the encoding process, and tested them in a whole-report design. Empirical data from four experiments in healthy individuals were fitted best by the parallel encoding model, even when items were presented unilaterally (processed within one hemisphere). Our results demonstrate that information from several items can be attentionally selected and consequently encoded into short-term memory simultaneously. This suggests the popular feature integration theory needs to be reformulated to account for parallel encoding, and provides important boundaries for computational models of short-term memory.

neuroscience↗

bioRxiv2018

Multi-target visual search organisation across the lifespan: Cancellation task performance in a large and demographically stratified sample of healthy adults

Highlights- Cancellation tasks are useful clinical tools that probe many cognitive modules\n- We used cancellation tests on 523 participants of different ages, sex, and education\n- We provide cancellation task norm scores for indices computed from a big sample\n- Cancellation indices include attention bias, processing speed and search organisation\n- About a quarter of the healthy population shows relatively disorganised search\n\n\nAbstractIt is important that accurate tests exist to assess cognition in various groups of individuals. One popular test of attention and executive functioning is the cancellation task, in which participants perform multi-target visual search to find and cancel targets among distractors. Although cancellation tasks have been used extensively with neurological patients, it is only partly clear whether performance is affected by demographic variables such as age and education, which can vary wildly among patients. Here, we describe performance in a sample of 523 healthy participants who participated in a web-based cancellation task. Specifically, we examined indices of spatial bias, processing speed, perseveration and revisiting behaviour, and search organisation. In this sample, age, sex, and level of education did not affect cancellation performance. A cluster analysis identified four cognitive profiles: Participants who make many omissions (N=18), who make many revisits (N=18), who have relatively poor search organisation (N=125), and who have relatively good search organisation (N=362). We advise neurologists and neuropsychologists to exercise caution when interpreting scores pertaining to search organisation in patients: Given the large proportion of healthy individuals with poor search organisation, disorganised search in patients might be pre-existing rather than disorder-related. Finally, we include norm scores for indices of spatial bias, perseverations and revisits, processing speed, and search organisation for a popular cancellation task.

neuroscience↗

bioRxiv2018

Beyond the vestibulo-ocular reflex: Vestibular input is processed centrally to achieve visual stability

The current study presents a re-analysis of data from Zink et al. (1998, Electroencephalography and Clinical Neurophysiology, 107), who administered galvanic vestibular stimulation through unipolar direct current. They placed electrodes on each mastoid, and applied both right and left anodal stimulation. Ocular torsion and visual tilt were measured under different stimulation intensities. New modelling introduced here demonstrates that directly proportional linear models fit reasonably well to the relationship between vestibular input and visual tilt, but not to that between vestibular input and ocular torsion. Instead, an exponential model characterised by a decreasing slope and an asymptote fitted best. These results demonstrate that in the results presented by Zink et al., ocular torsion could not completely account for visual tilt. This suggests that vestibular input is processed centrally to stabilise vision when ocular torsion is insufficient. Potential mechanisms and seemingly conflicting literature are discussed.

neuroscience↗