Nonlinear epigenetic variance: review and simulations

We present a review of empirical evidence that suggests that a substantial portion of phenotypic variance is due to nonlinear (epigenetic) processes during ontogenesis. The role of such processes as a source of phenotypic variance in human behaviour genetic studies is not fully appreciated. In addition to our review, we present simulation studies of nonlinear epigenetic variance using a computational model of neuronal network development. In each simulation study, time series for monozygotic and dizygotic twins were generated and analysed using conventional behaviour genetic modelling. In the results of these analyses, the nonlinear epigenetic variance was subsumed under the non-shared environmental component. As is commonly found in behaviour genetic studies, observed heritabilities and unique environmentabilities increased with time, whereas common environmentabilities decreased. The fact that the phenotypic effects of nonlinear epigenetic processes appear as unsystematic variance in conventional twin analyses complicates the identification and quantification of the ultimate genetic and environmental causes of individual differences. We believe that nonlinear dynamical system theories provide a challenging perspective on the development of individual differences, which may enrich behaviour genetic studies.     

How automatic is “automatic vigilance”? The role of working memory in attentional interference of negative information

Whereas attentional interference of negative information has previously been assumed to be automatic, the present research hypothesised that this effect depends on the availability of working-memory resources. In two experiments, participants judged the gender of angry versus happy faces. Working-memory load was manipulated by the presence or absence of a math task (Study 1) or mental rehearsal of a one- versus 8-digit number (Study 2). The results showed that angry faces interfered more with gender naming than happy faces, but only when working-memory load was low. As such, attentional interference of negative stimulus features can be modulated by top-down attentional control processes.     

Tuning down the hedonic brain: Cognitive load reduces neural responses to high-calorie food pictures in the nucleus accumbens

The present research examined whether cognitive load modulates the neural processing of appetitive, high-calorie food stimuli. In a functional magnetic resonance imaging (fMRI) study, participants quickly categorized high-calorie and low-calorie food pictures versus object pictures as edible or inedible while they concurrently performed a digit-span task that varied between low and high cognitive load (memorizing six digits vs. one digit). In line with predictions, the digit-span task engaged the dorsolateral prefrontal cortex (DLPFC) when cognitive load was high compared to low. Moreover, exposure to high-calorie compared to low-calorie food pictures led to increased activation in the nucleus accumbens (NAcc), but only when cognitive load was low and not when it was high. In addition, connectivity analyses showed that load altered the functional coupling between NAcc and right DLPFC during presentation of the high-calorie versus low-calorie food pictures. Together, these findings indicate that loading the cognitive system moderates hedonic brain responses to high-calorie food pictures via interactions between NAcc and DLPFC. Our findings are consistent with the putative cognitive nature of food motivation. Implications for future research are discussed.     

Gaze aversion during social interaction in preterm infants: a function of attention skills?

Preterm infants avert their gaze more often and for longer periods in early social interactions compared to full term infants. In previous studies this finding is interpreted as being a function of the higher degree of parental stimulation that is often found in parents of preterm children. The current study explores an additional hypothesis. Since the development of general visual attention abilities is found to be less optimal in preterm children, it is possible that less optimal maturation of attention abilities partially explains the elevated gaze aversion in a social context. Therefore, the current study investigated the association between gaze aversion in a social context and the ability to disengage and shift visual attention in a non-social context in 20 preterm and 42 full term infants aged 4 and 6 months. Results confirm that preterm infants are slower to shift their attention in a non-social context and that they avert their gaze more often in a social context compared to full term children. Furthermore, more frequent gaze aversion during social interaction at 6 months was related to longer disengagement and the shifting of attention at 4 and 6 months, but only within the preterm group. The results suggest that attention maturation is less optimal in preterm children; this can be observed in a non-social as well as a social context. Less attention maturation in preterm children can negatively influence the amount of time they can stay actively involved in social interaction.     

Clearing the mind: a working memory model of distraction from negative mood

The present research examined whether and how loading working memory can attenuate negative mood. In three experiments, participants were exposed to neutral, weakly negative, or strongly negative pictures followed by a task and a mood scale. Working memory demands were varied by manipulating task presence (Study 1), complexity (Study 2), and predictability (Study 3). Participants in all three experiments reported less negative moods in negative trials with high compared to low working memory demand. Working memory demands did not affect mood in the neutral trials. When working memory demands were high, participants no longer reported more negative moods in response to strongly negative pictures than to weakly negative pictures. These findings suggest that loading working memory prevents mood-congruent processing, and thereby promotes distraction from negative moods.