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Preferences for fat, sugar, and oral-sensory food qualities in monkeys and humans.
In humans and other primates, food intake depends on sophisticated, individualized preferences for nutrients and oral-sensory food qualities that guide decision-making and eating behavior. The neural and behavioral mechanisms for such primate-typical food preferences remain poorly understood, despite their importance for human health and their targeting by pharmacological obesity treatments. Here, we review a series of experiments that investigated how the biologically critical properties of foods-their nutrients (sugar, fat, protein) and oral-sensory qualities (viscosity, oral sliding friction)-influence food preferences in monkeys and humans. In an economic nutrient-choice paradigm, macaques flexibly trade nutrients and oral-sensory food qualities against varying food amounts, consistent with the assignment of subjective values. Nutrient-value functions that link objective nutrient content to subjective values accurately model these preferences, predict choices across contexts, and explain individual differences. The monkeys' aggregated choice patterns resulting from their nutrient preferences lead to daily nutrient balances that deviate from dietary reference points, resembling suboptimal human eating patterns when exposed to high-calorie foods. To investigate the sensory basis underlying nutrient values, we developed novel engineering tools that quantify food textures on oral surfaces, using fresh pig tongues. Oral-texture (i.e., mouthfeel) parameters, including viscosity and sliding friction, were shown to mediate monkeys' preferences for high-fat foods. When translated to human subjects, this approach revealed a neural mechanism for preferring high-fat foods from oral texture in the orbitofrontal cortex (OFC)-a key reward system of the brain. Importantly, human OFC responses to oral sliding friction in individual subjects-measured in the MRI scanner-predicted subsequent fat intake in a naturalistic, life-like eating test. These findings suggest that a primate nutrient-reward paradigm offers a promising approach for investigating the behavioral and neural mechanisms for human-typical food reward and food choice, to advance understanding of human eating behavior, overeating, and obesity.
Active information sampling in health and disease
Active information gathering is a fundamental cognitive process that enables organisms to navigate uncertainty and make adaptive decisions. Here we synthesise current knowledge on the behavioural, neural, and computational mechanisms underlying information sampling in healthy people and across several brain disorders. The role of cortical and subcortical regions spanning limbic, insular, fronto-parietal, and striatal systems is considered, along with the contributions of key neurotransmitters involving norepinephrine, dopamine, and serotonin. We also examine how various clinical conditions, including schizophrenia, obsessive-compulsive disorder, and Parkinson's disease have an impact on information gathering behaviours. To account for the findings, we outline a neuroeconomic perspective on how the brain may evaluate the costs and benefits of acquiring information to resolve uncertainty. This work highlights how active information gathering is a crucial brain process for adaptive behaviour in healthy individuals and how its breakdown is relevant to several psychiatric and neurological conditions. The findings have important implications for developing novel computational assays as well as targeted interventions in brain disorders.
Self- versus caregiver-reported apathy across neurological disorders
Abstract Apathy is a prevalent and persistent neuropsychiatric syndrome across many neurological disorders, significantly impacting both patients and caregivers. We systematically quantified discrepancies between self- and caregiver-reported apathy in 335 patients with a variety of diagnoses, frontotemporal dementia (behavioural variant and semantic dementia subtypes), Parkinson’s disease, Parkinson’s disease dementia, dementia with Lewy bodies, Alzheimer’s disease dementia, mild cognitive impairment, small vessel cerebrovascular disease, subjective cognitive decline and autoimmune encephalitis. Using the Apathy-Motivation Index (AMI) and its analogous caregiver version (AMI-CG), we found that caregiver-reported apathy consistently exceeded self-reported levels across all conditions. Moreover, self-reported apathy accounted for only 14.1% of the variance in caregiver ratings. This apathy reporting discrepancy was most pronounced in conditions associated with impaired insight, such as behavioural variant frontotemporal dementia, and was significantly correlated with cognitive impairment. Deficits in memory and fluency explained an additional 11.2% of the variance in caregiver-reported apathy. Specifically, executive function deficits (e.g., indexed by fluency) and memory impairments may contribute to behavioural inertia or recall of it. These findings highlight the need to integrate patient and caregiver perspectives in apathy assessments, especially for conditions with prominent cognitive impairment. To improve diagnostic accuracy and deepen our understanding of apathy across neurological disorders, we highlight the need of adapted apathy assessment strategies that account for cognitive impairment particularly in individuals with insight or memory deficits. Understanding the cognitive mechanisms underpinning discordant apathy reporting in dementia might help to inform targeted clinical interventions and reduce caregiver burden.
Goal-directedness deficit in Huntington's disease.
Apathy and impulsive behaviour co-occur in Huntington's disease (HD), but these debilitating behavioural syndromes are multidimensional constructs, raising the question of which specific dimensions drive this relationship and the stability of the co-occurring dimensions across time. People with HD and controls completed multidimensional apathy and impulsive behaviour scales at baseline and 1-year follow-up. A principal component analysis was performed on pooled data (n = 109) to identify components and factor loadings of subscales. Linear mixed models were used to examine differences in components between groups and timepoints. Three meaningful components emerged. Component 1 comprised positive loading for dimensions of apathy and impulsive behaviour pertaining to goal-directedness, namely attention, planning, initiation, and perseverance. In contrast, other dimensions of apathy and impulsive behaviour loaded onto components two and three in opposite directions. People with HD only scored worse than controls on the goal-directedness component. All components remained stable over time and closely resembled factors from the five-factor personality model. Component 1 mapped onto the factor conscientiousness, component 2 to extraversion, and component 3 to neuroticism. The clinical overlap between apathy and impulsive behaviour in HD relates to goal-directedness, whilst other dimensions of these constructs did not overlap.
Increased Sensitivity to Effort and Perception of Effort in People with Schizophrenia.
OBJECTIVE: Motivational deficits in schizophrenia are proposed to be attributable in part to abnormal effort-cost computations, calculations weighing the costs vs. the benefits of actions. Several reports have shown that people with schizophrenia display a reduced willingness to exert effort for monetary rewards when compared to controls. The primary goal of the current study was to further characterize reduced willingness to exert effort in schizophrenia by determining whether reduced willingness reflects (1) reduced sensitivity to reward, (2) increased sensitivity to effort, or (3) a combination of both. DESIGN: We assessed effort-cost decision-making in 30 controls and 30 people with schizophrenia, using 2 separate experimental tasks. Critically, one paradigm allowed for independent estimation of effects of reward and effort sensitivity on choice behavior. The other task isolated effort sensitivity by measuring effort in the absence of reward. Clinical interviews and self-report questionnaires were administered to people with schizophrenia to determine negative symptom severity. RESULTS: Across both tasks, we found evidence for reduced willingness to exert effort in people with schizophrenia compared to controls. Further, in both paradigms reduced willingness to exert effort was driven by increased sensitivity to effort in people with schizophrenia compared to controls. In contrast, measures of reward sensitivity did not significantly differ between groups. Surprisingly, we did not find correlations between task variables and measures of negative symptom severity. CONCLUSIONS AND RELEVANCE: These findings further specify prior work by identifying a specific contributory role for increased effort sensitivity in effort-cost decision-making deficits in schizophrenia.
Body posture as a measure of emotional valence in young children: a preregistered validation study
Introduction: Objective measures of emotional valence in young children are rare, but recent work has employed motion depth sensor imaging to measure young children's emotional expression via changes in their body posture. This method efficiently captures children's emotional valence, moving beyond self-reports or caregiver reports, and avoiding extensive manual coding, e.g., of children's facial expressions. Moreover, it can be flexibly and non-invasively used in interactive study paradigms, thus offering an advantage over other physiological measures of emotional valence. Method: Here, we discuss the merits of studying body posture in developmental research and showcase its use in six studies. To this end, we provide a comprehensive validation in which we map the measures of children's posture onto the constructs of emotional valence and arousal. Using body posture data aggregated from six studies (N = 466; Mage = 5.08; range: 2 years, 5 months to 6 years, 2 months; 220 girls), coders rated children's expressed emotional valence and arousal, and provided a discrete emotion label for each child. Results: Emotional valence was positively associated with children's change in chest height and chest expansion: children with more upright upper-body postures were rated as expressing a more positive emotional valence whereas the relation between emotional arousal and changes in body posture was weak. Discussion: These data add to existing evidence that changes in body posture reliably reflect emotional valence. They thus provide an empirical foundation to conduct research on children's spontaneously expressed emotional valence using the automated and efficient tool of body posture analysis.
Modeling social cohesion with coupled oscillators: Synchrony and fragmentation
Maintaining cohesion is a fundamental challenge in group-living species, where individuals must balance their own activity schedules with the demands of social interactions. In this paper, we model group dynamics using a network of semi-coupled oscillators to investigate how differences in activity schedules impact social cohesion and fragmentation. By introducing parameters for social “stickiness” (interaction strength) and activity synchronization, we simulate group behavior across varying conditions. Our findings reveal that, mathematically, cohesive groups can fragment when individual schedules diverge beyond critical thresholds, and that increasing social stickiness mitigates this effect. We explore these dynamics in the context of group size, subgroup formation, and coupling parameters, drawing parallels to network cohesion and fragmentation in human and artificial social systems. These results highlight the role of synchronization in maintaining stable social structures and suggest future avenues for empirical validation and application in broader social network contexts.
The curious transference of sensations in the ‘mismatched-palm’ rubber hand illusion
We describe a disconcerting illusion. The participant looks at the palm of a left rubber hand being touched while receiving synchronous touch on the back of their own hidden right hand. Despite postural incongruence, mismatching handedness and touch being at a different location on the viewed and hidden hands, participants experience the illusion of ownership of the rubber hand and the illusion of feeling touch on the rubber hand. The robustness of the rubber hand illusion to seemingly profound incongruencies is explained with reference to Riemer et al.’s four basic principles for successful embodiment.
Microstructural Properties of the Cerebellar Peduncles in Children With Developmental Language Disorder.
Children with developmental language disorder (DLD) struggle to learn their native language for no apparent reason. While research on the neurobiological underpinnings of the disorder has focused on the role of corticostriatal systems, little is known about the role of the cerebellum in DLD. Corticocerebellar circuits might be involved in the disorder as they contribute to complex sensorimotor skill learning, including the acquisition of spoken language. Here, we used diffusion-weighted imaging data from 77 typically developing and 54 children with DLD and performed probabilistic tractography to identify the cerebellum's white matter tracts: the inferior, middle, and superior cerebellar peduncles. Children with DLD showed lower fractional anisotropy (FA) in the inferior cerebellar peduncles (ICP), fiber tracts that carry motor and sensory input via the inferior olive to the cerebellum. Lower FA in DLD was driven by lower axial diffusivity. Probing this further with more sophisticated modeling of diffusion data, we found higher orientation dispersion but no difference in neurite density in the ICP of children with DLD. Reduced FA is therefore unlikely to be reflecting microstructural differences in myelination, rather the organization of axons in these pathways is disrupted. ICP microstructure was not associated with language or motor coordination performance in our sample. We also found no differences in the middle and superior peduncles, the main pathways connecting the cerebellum with the cortex. To conclude, it is not corticocerebellar but atypical olivocerebellar white matter connections that characterize DLD and suggest the involvement of the olivocerebellar system in speech and language acquisition and development.
The effectiveness of positive psychology-based interventions in prisons on well-being: a systematic review and meta-analysis
Positive psychology-based interventions (PPIs) have shown promising evidence for improving psychological well-being in a variety of contexts and are consistent with calls for strengths-based interventions in correctional settings. While these interventions have been tested in prison settings, no study has empircally assessed effectiveness of PPIs for improving psychological well-being in prisons. In this study, we conducted a systematic review and meta-analysis on the effects of PPIs on psychological well-being in prisons. 9 studies (4 RCTs) were included, representing 662 participants. We found large, significant effects on psychological well-being in comparison with control arms (Hedge’s g = 0.76). Additionally, we found large, significant within-group effects (Hedge’s g = 0.66) on psychological well-being. The overall quality of included studies was poor, however, limiting the certainty of these findings. Our findings indicate that positive psychology-based interventions can significantly improve psychological well-being in prison settings.