Interoception and disordered eating: A systematic review.

Deficits in interoception have been associated with disordered eating but there has been no systematic review of whether the interoceptive deficits are observed across all types of disordered eating and across interoceptive modalities. There has also been no evaluation of whether deficits in interoception play a causal role in the development of disordered eating. Nor has there been a review of the moderating/mediating factors of the relationship between interoception and disordered eating. To address these gaps we conducted a systematic review using PRISMA guidelines. 104 studies with 32883 participants were included. Deficits in interoception were observed across disordered eating types and interoceptive modalities suggesting that interoception may constitute a transdiagnostic feature of disordered eating. There is currently limited evidence on the causal role of interoception in the development of disordered eating and no studies have formally analysed the moderators/mediators. Future mechanistic research examining particular dimensions of interoception will provide insights into the specific interoceptive deficits associated with disordered eating and could lead to the development of improved therapies.

Diabetes dietary management alters responses to food pictures in brain regions associated with motivation and emotion: a functional magnetic resonance imaging study.

AIMS/HYPOTHESIS: We hypothesised that living with type 2 diabetes would enhance responses to pictures of foods in brain regions known to be involved in learnt food sensory motivation and that these stronger activations would relate to scores for dietary adherence in diabetes and to measures of potential difficulties in adherence. METHODS: We compared brain responses to food images of 11 people with type 2 diabetes and 12 healthy control participants, matched for age and weight, using functional magnetic resonance imaging (fMRI). RESULTS: Having type 2 diabetes increased responses to pictured foods in the insula, orbitofrontal cortex (OFC) and basal ganglia and, within these regions, the effect of the fat content of the foods was larger in participants with type 2 diabetes than in healthy controls. Furthermore, increased activation to food within the insula and OFC positively correlated with external eating, dietary self-efficacy and dietary self-care. In contrast, responses within subcortical structures (amygdala and basal ganglia) were positively correlated with emotional eating and rated appetite for the food stimuli and negatively correlated with dietary self-care. CONCLUSIONS/INTERPRETATION: Type 2 diabetes is associated with changes in brain responses to food that are modulated by dietary self-care. We propose that this is linked to the need to follow a life-long restrictive diet.

Neural correlates of processing valence and arousal in affective words.

Psychological frameworks conceptualize emotion along 2 dimensions, "valence" and "arousal." Arousal invokes a single axis of intensity increasing from neutral to maximally arousing. Valence can be described variously as a bipolar continuum, as independent positive and negative dimensions, or as hedonic value (distance from neutral). In this study, we used functional magnetic resonance imaging to characterize neural activity correlating with arousal and with distinct models of valence during presentation of affective word stimuli. Our results extend observations in the chemosensory domain suggesting a double dissociation in which subregions of orbitofrontal cortex process valence, whereas amygdala preferentially processes arousal. In addition, our data support the physiological validity of descriptions of valence along independent axes or as absolute distance from neutral but fail to support the validity of descriptions of valence along a bipolar continuum.

A critique of functional localisers.

In this critique, we review the usefulness of functional localising scans in functional MRI studies. We consider their conceptual motivations and the implications for experimental design and inference. Functional localisers can often be viewed as acquiring data from cells that have been removed from an implicit factorial design. This perspective reveals their potentially restrictive nature. We deconstruct two examples from the recent literature to highlight the key issues. We conclude that localiser scans can be unnecessary and, in some instances, lead to a biased and inappropriately constrained characterisation of functional anatomy.

Feeling or features: different sensitivity to emotion in high-order visual cortex and amygdala.

Emotionally loaded visual stimuli have shown increased activation in visual and cortex limbic areas. However, differences in visual features of such images could confound these findings. In order to manipulate valence of stimuli while keeping visual features largely unchanged, we took advantage of an "expressional transfiguration" (ET) effect of faces. In addition, we used repetition effects, which enabled us to test more incisively the impact of the ET effect. Using the ET manipulation, we have shown that the activation in lateral occipital complex (LOC) was unaffected by valence attributes, but produced significant modulation of fMR adaptation. Contrary to LOC, amygdala activation was increased by ET manipulation unrelated to the adaptation. A correlation between amygdala and LOC adaptation points to a possible modulatory role of the amygdala upon visual cortex short-term plasticity.

Emotion-perception interplay in the visual cortex: "the eyes follow the heart".

Emotive aspects of stimuli have been shown to modulate perceptual thresholds. Lately, studies using functional Magnetic Resonance Imaging (fMRI) showed that emotive aspects of visual stimuli activated not only canonical limbic regions, but also sensory areas in the cerebral cortex. However, it is still arguable to what extent such emotive, related activation in sensory areas of the cortex are affected by physical characteristic or attribute difference of stimuli. To manipulate valence of stimuli while keeping visual features largely unchanged, we took advantage of the Expressional Transfiguration (ET) of faces. In addition, to explore the sensitivity of high level visual regions, we compared repeated with unrepeated (i.e. different) stimuli presentations (fMR adaptation). Thus, the dynamics of brain responses was determined according to the relative signal reduction during "repeated" relative to "different" presentations ("adaptation ratio"). Our results showed, for the first time, that emotional valence produced significant differences in fMR adaptation, but not in overall levels of activation of lateral occipital complex (LOC). We then asked whether this emotion modulation on sensory cortex could be related to previous personal experience that attached negative attributes of stimuli. To clarify this, we investigated Posttraumatic Stress Disorder (PTSD) and non-PTSD veterans. PTSD is characterized by recurrent revival of trauma-related sensations. Such phenomena have been attributed to a disturbed processing of trauma-related stimuli, either at the perceptual level or at the cognitive level. We assumed that PTSD veterans would differ from non-PTSD veterans (who have similar combat experience) in their high order visual cortex responses to combat-related visual stimuli that are associated with their traumatic experience. An fMRI study measured the cerebral activation of subjects while viewing pictures with and without combat content, in "repeated" or "different" presentation conditions. The emotive effect on the visual cortex was found, again, only in the fMR-adaptation paradigm. Visual cortical regions showed significant differences between PTSD and non-PTSD veterans only in "repeated" presentations of trauma-related stimuli (i.e. combat). In these regions, PTSD veterans showed less decrease in signal with repeated presentations of the same combat-related stimuli. This finding points to the possibility that traumatic experience modulates brain activity at the level of sensory cortex itself.