Diet and Interoception

This study published in 2017 investigated the impacts of briefly consuming a high fat with high sucrose (HFS) diet over 4 days relative to one lower in saturated fat and added sugar, on hippocampal-dependent learning and memory (HDLM) and perception of internal bodily state (interoception). A group of healthy individuals were randomly assigned to either the Experiment condition (HFS breakfast) or the control condition, and were assessed before and after breakfast on day one and four on HDLM, interoception and biological measures. Food diaries were also completed before and during the study. The results showed significant reductions in HDLM and reduced interoceptive sensitivity to hunger and fullness among the Experimental condition group, in comparison with the control group. The greater reductions in HDLM was associated with the larger changes in blood glucose across breakfast. Those assigned to the experimental condition exhibited markedly different blood glucose and triglyceride responses to their breakfast relative to the control group. The Experimental condition compensated for their energy-dense breakfast by reducing carbohydrate intake, while saturated fat intake remained consistently higher than Controls. Attuquayefio et. al (2017) claims to have replicated the results of animal studies in humans in the way a Western-style diet impacts HDLM, and concludes that the link between diet-induced HDLM changes and blood glucose suggests one pathway by which diet impacts HDLM in humans. [NPID: interoception, high fat, high sugar, HDLM, hippocampal-dependent learning and memory, hippocampus, food diary, interoceptive awareness, blood glucose, glucose, carbs, Western-style diet, WS diet]

Sample et. al (2016) conducted three studies with the aim of investigating how food-related external cues may overwhelm internal cues that normally regulate energy intake, thought to occur in obesogenic environments. With the first experiment demonstrating rats’ ability to predict sucrose delivery using stimuli arising from 0 to 4 hours food deprivation, the second experiment examined the ability of these deprivation cues to compete with external cues, and how consuming a Western-style diet (WD) impacts that competition. The rats were trained to use both their deprivation cues and external cues as compound discriminative stimuli, before being split into two groups: one half of the rats were then placed on WD while the other half remained on chow, and external cues were removed to assess learning about deprivation state cues. When the external cues were removed, chow-fed rats continued to discriminate using only deprivation cues, while WD-fed rats did not and actually performed similarly to control groups trained with a non-contingent relationship between deprivation cues and sucrose reinforcement. The writers pointed out that previous studies had discovered discrimination based on interoceptive deprivation cues depends on the hippocampus and that the consumption of the WD could interfere with hippocampal functioning. The final third experiment conducted assessed the effects of neurotoxic hippocampal lesions on weight gain and on sensitivity to the appetite-suppressing effects of the satiety hormone cholecystokinin (CCK). Relative to controls, hippocampal-lesioned rats gained more weight and showed reduced sensitivity to 1.0ug CCK doses but not 2.0 or 4.0ug. These findings suggest that WD intake reduces utilisation of interoceptive energy state signals to regulate appetitive behavior via a mechanism that involves the hippocampus. [NPID: interoception, external eating, external cues, obesity, sucrose delivery, sucrose, Western-style diet, WS diet, animal studies, animal, hippocampus]

Quadt et. al (2018) presented a neurobiological overview of interoception (the sensing of internal bodily sensations) and described how interoceptive impairments at different levels relate to specific physical and mental health conditions (such as sickness behaviors and fatigue, depression, eating disorders, autism, and anxiety). This review shows that systematic investigation of how individual differences, and within-individual changes, in interoceptive processing can contribute to the mechanistic understanding of physical and psychological disorders. The findings were framed in an interoceptive predictive processing framework and highlight potential new avenues for treatments. [NPID: interoception, fatigue, depression, eating disorders, autism, anxiety, psychological disorders]

Although there is evidence that people who consume a diet rich in saturated fat and added sugar show less sensitive interoception for hunger and fullness, this 2015 study aimed to find out whether sensitive thirst interoception is reduced in those who routinely consume these diets also. The subjects involved, who all varied mostly in diet, were made thirsty by eating salted chips and were later provided with as much water as desired, with thirst ratings obtained throughout. Eating habits, memory and executive function were all determined, while a self-report measure of interoceptive awareness was also included. A diet reported as richer in saturated fat and added sugar (an HFS diet) was associated both with less sensitive thirst interoception and with greater attention to somatic signs, while there was also evidence of poorer hippocampal-sensitive learning and memory detected. Poorer sensitivity to interoceptive cues appeared to be a reliable correlate of an HFS diet, the causal origins of which were discussed by this study. [NPID: interoception, interoceptive awareness, thirst, memory, executive function, sugar, somatic signs] [NPID: interoception, interoceptive awareness, thirst, memory, function, saturated fat, sugar, somatic signs, HDLM, hippocampus]

Stevenson, Mahmut & Rooney (2015) examined whether there are individual differences in several aspects of and possible causes of ingestion-related interoception (ability to perceive internal bodily states) such as signals from the viscera, motivational states, affective reactions, as well as associated cognitions. Individual variation in almost all aspects of interoception was documented for hunger, fullness and thirst - including how participants use, prioritise and integrate visceral, motivational, affective and cognitive information. The review found variation between individuals may arise from multiple causes, including genetic influences, developmental alterations thought to possibly result from child feeding practices, and from conditions such as depression, anxiety, eating disorders and certain subtypes of obesity. Ingestion-related interoception could also be affected by diets with low nutritional value and dietary restraint. The practical and theoretical consequences of these individual differences are discussed in this review. Stevenson et. al (2015) stated that certain forms of brain injury (notably to the temporal lobes) are associated with impaired ingestion-related interoception. [NPID: interoception, interoceptive awareness, viscera, motivational states, affective reactions, cognition, hunger, fullness, thirst, depression, anxiety, eating disorders, brain injury]

This 2016 paper proposes a definition of interoception as based on subjective experience since the meaning has changed over the course of a century (from the restrictive to the inclusive) and Ceunen et. al (2016) feel there is a need for an overarching concept. Many aspects such as physical cause of a sensation efferent innervation, afferent pathways of the tissue can make any particular interoceptive sensation unique from any other interoceptive sensation, but the authors explain that primarily in its overarching meaning, interoception is a product of the central nervous system and is a construct based on an integration of various sources and not just afferent information for example. This paper asks for the use of specific vocabulary in addressing the many aspects that contribute to interoception. [NPID: interoception, interoceptive awareness, subjective experience, interoception sensation, CNS, central nervous system, vocabulary]

This 2016 study explored the possible association between interoceptive awareness with performance on a hippocampal dependent learning and memory (HDLM) measure in logical memory percent retention, among healthy young adults. Interoceptive awareness was assessed on three tasks: heart rate tracking; water loading and the Multidimensional Assessment of Interoceptive Awareness Questionnaire (MAIA). After controlling for potentially confounding variables, significant associations were revealed between HDLM performance and MAIA measures as well as water loading. These results implicate the role of hippocampal dependent processes in interoceptive awareness in healthy young adults, and may suggest the medial temporal lobe structures regulate interoceptive tasks (which includes ingestion). [NPID: interoception, interoceptive awareness, ingestion, HDLM, hippocampal dependent learning and memory, HDLM, heart rate tracking, water loading, medial temporal lobe]

Although there are many factors that predispose people to weight gain and obesity, this 2017 review focused on two ways in which eating behavior may be influenced by sensitivity to interoceptive signals of hunger, satiety, and metabolic energy reserves. The findings of this review indicated that obesity may be related to altered interoception: firstly Simmons and DeVille (2017) brought up possible relevance of hypersensitivity to interoceptive signals of hunger, which would lead to positive alliesthesia (pleasant or unpleasant perception of external stimulus) for food cues that undermine attempts to change unhealthy eating behaviors. Secondly, it could be that overeating and obesity arise from an inability to accurately detect interoceptive signals of satiety and positive energy balance. It was concluded that continued development of novel obesity interventions with the purpose of promoting interoception awareness is warranted. [NPID: interoception, interoceptive awareness, hunger, satiety, metabolic energy reserves, altered interoception, positive alliesthesia, external stimulus, overeating, satiety]

Young et. al (2017) designed two studies both on eating behavior and interoception since “at present it is unclear which aspects of interoception contribute to aberrant eating behaviour and obesity”. The first study used the novel interoceptive indices [interoceptive metacognitive awareness (IAw) and interoceptive prediction error (IPE)] and the traditional measures such as interoceptive accuracy (IAc) and interoceptive sensibility (IS), and examined their links with eating behavior and body mass index (BMI). The results confirmed the dissociation between these interoceptive indices: emotional eaters were characterised by a heightened interoceptive signal but reduced mega-cognitive awareness of their interoceptive abilities; and emotional eating was found to correlate with IPE but this effect could not be accounted for by differences in anxiety and depression. The second study verified the positive association between interoceptive accuracy and emotional eating using a new non-biased heartbeat discrimination task (based on the method of constant stimuli). The findings from study two included new and important mechanistic insights into the processes that may underlie problematic affect regulation in those overweight. [NPID: interoception, interoceptive awareness, obesity, metacognitive awareness, interoceptive prediction error, emotional eating, anxiety, depression, heartbeat discrimination task]

Oswald, Chapman & Wilson (2017) explored the mechanisms underlying the poorly understood relationship between body appreciation and intuitive eating by collecting online survey data from 200 Australian female college students. This study tested whether two partially independent, self-reported facets of interoceptive ability: 'interoceptive awareness' (defined as the ability to detect internal bodily cues) and 'interoceptive responsiveness' (the way in which individuals value and respond to these cues) mediated the relationship between body appreciation and three subscales of intuitive eating: 'unconditional permission to eat'; 'reliance on internal hunger and satiety cues', and 'eating for physical rather than emotional reasons'. It was discovered that interoceptive awareness partially mediated the relationship between body appreciation and 'reliance on internal hunger and satiety cues', while interoceptive responsiveness partially mediated the relationship between all three subscales of intuitive eating. These findings support and actually extend the theoretical framework of the acceptance model of intuitive eating by suggesting that the different facets of intuitive eating may have distinct underlying mechanisms. [NPID: interoception, interoceptive awareness, body appreciation, intuitive eating, body appreciation, physical hunger, satiety]

Since there have been suggestions that interoception (perception of bodily signals) and interoceptive sensitivity (sensitivity for internal signals) might play crucial roles when it comes to regulation of behavior associated with feelings of satiety, Herbert & Pollatos (2014) examined interoceptive sensitivity among 75 overweight and obese women and men (using a heartbeat detection task) and compared them to normal weight controls. The hypothesis before the initiation of the study that overweight and obese would be related to attenuated interoceptive sensitivity was proved right, with evidently higher scores seen for those normal weight participants compared to overweight + obese. In addition, a negative correlation was identified between the BMI and interoceptive sensitivity in the overweight and obese groups only. In the conclusion section, Herbert and Pollatos (2014) writes that presumably, interoceptive sensitivity interacts with the regulation of food intake in everyday life in part by promoting the detection of bodily changes accompanying satiety, the signals of which may be poorly detected by overweight and obese individuals. [NPID: interoception, interoceptive awareness, interoceptive sensitivity, heartbeat detection task, obesity, satiety]

Due to the “poorly understood” relation between interoception and body image according to Badoud & Tsakiris (2017), this review presents behavioral and neuroimaging evidence from non-clinical and clinical populations to propose that basic interoceptive processes and interoceptive awareness may greatly contribute to the complex formation of body image and its disturbances. The purpose of this review was to integrate both interoceptive and exteroceptive representations of the body, and in doing so, suggested links mentioned between interoception and body image can inform “new empirically testable hypotheses on the underlying neurocognitive processes that are central to body image concerns and disturbances, and motivate relevant clinical implications”. [NPID: interoception, interoceptive awareness, body image, neurocognitive processes]

Sample et. al (2015) addresses the “obesogenic environments” commonly found in the western and westernised societies and the hypothesis that the external cues (that characterise obesogenic environments) associated with highly palatable, energy-dense foods may elicit such powerful changes in appetitive and eating behavior that the internal physiological mechanisms that helps maintain energy balance may become overwhelmed. Sample and others (2015) therefore undertook two experiments to investigate a learning mechanism that may underlie the supposed loss of internal control (relative to external). The first experiment involved rats provided with external stimuli (auditory cues) and varying levels of food deprivation (internal stimuli), both of which could be used to solve a simple discrimination task. Yet, deprivation cues ended up gaining substantial discriminative control over conditioned responding. Whereas, experiment 2 found that in comparison to standard chow, maintenance on a "western-style" diet high in saturated fat and sugar weakened discriminative control by food deprivation cues, but did not impair learning when external cues were also trained as relevant discriminative signals for sucrose. The researchers concluded that eating a western-style diet contributed to a loss of internal control over appetitive behavior relative to external cues, and discussed how interference of hippocampal-dependent learning and memory processes may be the cause of this relative loss of control by food deprivation signals. This would form the basis of a vicious-cycle of excessive consumption, body weight gain, and progreesive cognitive decline that could begin “very early” in life. [NPID: interoception, interoceptive awareness, body image, internal control, control, HDML, hippocampus, Western-style diet, WS diet, cognitive decline]

Since some people believe that the insula and its surroundings neural circuits are responsible for not just interoception but attention, awareness, and all subjective experiences (much of which have been linked to the mindfulness literature) and due to the fact that interoception and mindfulness literature (and meditation) remain broadly defined (often without precision), Gibson (2019) here states that it is more accurate to link many of the identified benefits in the mindfulness literature to interoception and its neurological correlates. The author also proposes attentional style as a means to clarify some of the confusion surrounding mindfulness, interoception, and meditation. Gibson (2019) believes each meditation can provide a unique perspective from which to investigate complex interoceptive signals that may be unavailable from other meditative traditions. [NPID: interoception, interoceptive awareness, insula, attention, awareness, meditation, mindfulness]

Stevenson & Francis (2017) reviewed known, suspected and newly hypothesised hippocampal-dependent functions involved in regulating food intake and for each, evidence was presented for hippocampal involvement, its putative regulatory role was described, and hypothesised effects of hippocampal impairment were also discussed. These functions dependent on the hippocampus of the brain included: declarative memory processes, and their use in explicitly evaluating when, what and how much to eat; interoception, (since it relates to hunger, fullness and thirst); inhibitory processes and their role in modulating memory retrieval; craving and imagery for food; perception of time and its involvement in the preparation of the body for food consumption and estimating meal length; trace conditioning and nutrient-related learning; and inhibition of the hypothalamic-pituitary-adrenal stress response and stress-related eating. It was concluded that the hippocampus is involved in the regulation of food intake via multiple interconnected pathways, many of which are either understudied or not studied yet. [NPID: interoception, interoceptive awareness, hippocampus, memory, hunger, fullness, thirst, meal length, stress]

This 2019 research study conducted 4 focus group interviews to analyse and understand consumers’ reflections on post-ingestive sensations, which are ‘the subjective perceptions of the body after eating’. A total of thirty consumers took part in the focus groups, and were diversified in terms of age, gender, and body mass index (BMI). The results were made up of the consumers’ retrospective reports divided into four key themes including energy sensations, satiety sensations, wellbeing and desires. Within energy sensations, consumers differentiated between two sub-groups of sensations, namely sensations related to a positive general energy level and sensations related to a negative low energy level, while satiety sensations consisted of typical satiety and extreme satiety described by the consumers. Sensations related to extreme satiety were in general more detectable than typical satiety sensations. Wellbeing was broadly summarised as “feeling good” and often reported were positive sensations such as sensing pleasure and happiness after eating, while “desires” was typically something more or something else than just consumed. Duerland et. al (2019) found that post-ingestive sensations function as important parameters when it comes to understanding the whole consumer experience. These results could also be applied in real eating contexts to explore even greater implications and importance in food choice and dietary behavior. [NPID: interoception, interoceptive awareness, well-being, consumer experience, food choice, decision making]

Deurland et. al in 2020 conducted these two in-country consumer studies to compare Chinese and Danish consumers in their post-ingestive drivers of Post-Ingestive Food Pleasure (PIFP), which was defined as a “subjective conscious sensation of pleasure and joy experienced after eating”. The post-ingestive sensations and PIFP of the 48 participants from Denmark and the 53 from China were measured for three hours following consumption of a breakfast meal. Key results revealed perceived Satisfaction, Mental, Overall and Physical wellbeing to be highly influential on PIFP in both countries. The Danish consumers, in particular, perceived appetite-related sensations such as satiety, hunger, desire-to-eat and in-need-of-food to be influential on PIFP. Whereas in China, drivers of FIPF were more vitality-related sensations like energised, relaxation and concentration. There were similarities but also distinct subtleties in the cultural constructs of PIFP in Denmark and in China. Deurland et. al (2020) concluded that food pleasure as a post-ingestive measure provides valuable output. [NPID: interoception, interoceptive awareness, China, Danish, pleasure, vitality, energy, relaxation, concentration, Denmark]

Looking particularly at subjective sensations as determinants of food choices can provide important insights into dietary behaviors, which is why Deurland et. al (2020) in this study explored subjective sensations, specifically those linked to appetite, desire, wellbeing and energy. The purpose was to quantify subjective temporal sensations, and examine the effects of these sensations on snack choice. The two-hundred and fifty three subjects (with ana average age of 20.5) reported their subjective sensations, before they were offered a choice of one out of six snacks. Choices were recorded as implicit choice measures, and were shown to be affected, either positively or negatively, by sensory specific desire measures (salty, fatty, sweet desire) in particular. Also, wellbeing sensations for example overall, mental, and physical wellbeing had significant impacts on snack choice. This study has proven the importance of sensory specific desires and wellbeing sensations in determining our food choices, and could have broader implications concerning public health issues and obesity. [NPID: interoception, interoceptive awareness, food choice, decision-making, appetite, desire. Well-being, energy, snacking, public health issues, obesity]

In this study undertaken in 2019, the aim was to quantify the dynamics of different post-ingestive sensations after eating as well as to study the effect of protein and carbohydrate on hedonic (pleasant/unpleasant) and post-ingestive responses. Using a randomised controlled crossover design, forty-eight participants (mean age 20.4) had a high in protein (HighPRO) or high in carbohydrate (HighCHO) breakfast on two separate days. Post-ingestive sensations were then reported every 30 minutes for three hours following consumption. The results indicated HighCHO, in comparison to HighPRO, induced greater hedonic responses and scored higher ratings for post-ingestive sensations such as satisfaction, food joy, overall wellbeing, and fullness. Although, HighPRO achieved higher ratings for sweet desire post intake. Also a significant main effect of time was demonstrated for all post-ingestive sensations. The study proposes the development of sensations post-meal might be crucial for the consumers’ food choices and for extra calorie intake. [NPID: interoception, interoceptive awareness, hedonic, post-ingestive sensations, satisfaction, food joy, overall well-being, fullness]

Khalsa et. al (2018) refers to interoception as a process by which the central nervous system senses, interprets, and integrates signals starting from within the body, and links its dysfunction with several mental health conditions such as anxiety, mood, eating, addictive and somatic symptom disorders. Due to the difficulty broadly applying interoceptive constructs in mental health research and treatment settings, a group of interoceptive experts met up in November 2016 with the primary aim of rapidly gathering information and getting to understand the role of interoception in mental health. This review article summarised what the group of experts agreed on with regards to interoception’s overall role. [NPID: interoception, interoceptive awareness, CNS, anxiety, mood, addiction, somatic symptom disorder]

Stevenson, Mahmut & Rooney (2015) examined whether there are individual differences in several aspects of and possible causes of ingestion-related interoception (ability to perceive internal bodily states) such as signals from the viscera, motivational states, affective reactions, as well as associated cognitions. Individual variation in almost all aspects of interoception was documented for hunger, fullness and thirst - including how participants use, prioritise and integrate visceral, motivational, affective and cognitive information. The review found variation between individuals may arise from multiple causes, including genetic influences, developmental alterations thought to possibly result from child feeding practices, and from conditions such as depression, anxiety, eating disorders and certain subtypes of obesity. Ingestion-related interoception could also be affected by diets with low nutritional value and dietary restraint. The practical and theoretical consequences of these individual differences are discussed in this review. Stevenson et. al (2015) stated that certain forms of brain injury (notably to the temporal lobes) are associated with impaired ingestion-related interoception. [NPID: interoception, interoceptive awareness, viscera, motivational states, individual variation, depression, anxiety, eating disorders, obesity, child feeding practices, temporal lobes]

This 2018 quantitative cross-sectional descriptive study evaluated the intensity and discomfort of perioperative (occurring around/at the time of an operation) thirst and related factors during anaesthesia recovery. Of the 203 individuals recruited, 89.6% (182) reported thirst. The mean intensity of thirst was 6.9 measured using a verbal numerical scale of 0 to 10 and discomfort was 7.3 on a scale of 0 to 14. Moreover, dry mouth and desire to drink was reported in 87.3% of the sample population, with 79.1% complaining of dry lips, thick tongue feeling (43.4%), thick saliva (56.5%), dry throat (75.2%), and bad taste in the mouth (63.1%). A positive correlation was confirmed between intensity of thirst and discomfort (assessed by the scale). Although no association was found between age, length of fasting, and use of opioids with the intensity of thirst and discomfort, the increase in thirst intensity linked to discomfort could possibly have big implications in clinical practice. [NPID: interoception, interoceptive awareness, thirst, opioids]

Critchley & Garfinkel (2017) believes our understanding of emotions and its disorders is growing thanks to greater comprehension of interoception, which means the afferent signalling (mode in which stimuli is sent to the brain), central processing, plus internal body signals interpreted in mental and neural form. The authors describe the new insights discovered concerning interoception and the way it contributes to emotion. They include short-term interoceptive effects on neural and mental processes, the recognition of distinguishable psychological aspects of interoception, and models that explain emotions and selfhood (social construction of self). [NPID: interoception, interoceptive awareness, emotion, afferent signaling, self, selfhood, social construction of self]

Lischke et. al (2020) thought about the possibility that interoception contributes to the regulation of emotions, and thus designed this study to investigate the relationship between interoception and emotional regulation in a healthy population of 84. The researchers describe their heartbeat detection task and self-report questionnaire used to assess interoceptive accuracy and emotion regulation in this study as similar to their previous research. What was done differently was the sample population were analysed by sex and controls were used for individual characteristics that could potentially affect the relationship between the interoception and emotion outcomes. The results showed a correlation between interoceptive accuracy with reappraisal but not with suppression in the male subjects, while interoceptive accuracy was not related to neither reappraisal nor suppression in female individuals. Although it appears that interoception is crucial in the regulation and experience of emotions, these findings imply the greater complexity of the relationship between interoception and emotional regulation than previously reported. [NPID: interoception, interoceptive awareness, emotional regulation, heartbeat detection, regulation, emotion, emotional regulation]

Hargrave et. al (2016) explains that one of the roles of the hippocampus is to inhibit responding to previously rewarded cues with the use of context such as interoceptive satiety states. Constantly consuming during states of positive energy balance leads to weight gain and obesity. Research has implicated Western diets in several types of hippocampal dysfunction including reduced expression of neurotrophins (induce neural survival, development and function) and nutrient transporters, increased inflammation, microglial activation (involved in immune response), and blood brain barrier permeability. Since hippocampal dysfunction is associated with an animal’s inability to modulate responding to previously reinforced cue, this paper proposes that such deficits promote overeating, which can exacerbate hippocampal impairment, and start a vicious cycle of obesity and cognitive decline. [NPID: interoception, interoceptive awareness, hippocampus, reward, satiety, weight gain, obesity, Western-style diet, inflammation, microglial activation, blood brain barrier, hippocampal dysfunction, overeating, cognitive decline]

Parcet et. al (2020) explains that sensitivity to reward can predispose a person to addictive behaviors and even risky behaviors that facilitates uncontrolled eating but there has not been much attention put on the direct relationship between these two factors. This is why this study took T1-weighted images (a pulse sequence in MRI) and measured reward sensitivity and BMI of 206 adults, with the intention to discover whether the coexistence of high BMI and high reward sensitivity structurally changes brain areas specifically involved in the regulation of dietary behavior. The neuroimaging results showed a relationship between BMI and reduced volume in the medial and lateral orbitofrontal cortex, and also confirmed one between reward sensitivity and lower striatum volume. Importantly, there was evidence that the interaction between the two factors was significantly related to the right anterior hippocampus volume, indicating the associations between stronger reward sensitivity and a higher BMI with reduced hippocampal volume. The conclusion was drawn that hippocampal dysfunction may contribute to maintaining a vicious cycle that predisposes people to obesity. [NPID: interoception, interoceptive awareness, addictive behaviors, uncontrolled eating, reward, medial cortex, lateral orbitofrontal cortex, reward sensitivity, hippocampus]

Kleckner et. al (2017) here introduces a system, conceptually similar to the large-scale intrinsic brain system involving senses such as sight and hearing for example, to represent sensations from within the body known as interoception. The group of researchers behind this study also relate this system with the regulating peripheral systems in the body called allostasis. The existence of an intrinsic allostatic/interoceptive system in the brain was evaluated using tract-tracing studies of macaque monkeys, two magnetic resonance imaging samples totalling 550 entries, and a new Embodied Predictive Interoception Coding (EPIC) model. After evaluating another sample of 41, it was proven that individuals with stronger connectivity between system hubs performed better in terms of interoceptive ability. Kleckner et. al (2017) provide new insights for the brain’s functional architecture and claims to have possibly united mental and physical illness. [NPID: interoception, interoceptive awareness, allostasis]

Harshaw (2015) believes researching interoception (perception and interpretation of bodily signals) could lead the way in understanding the links between the social, cognitive-affective and somatic features of depression. In this paper, he reviews the growing evidence that somatic signaling and interoception are altered in depressed individuals. The evidence included comparative studies that observed the effects mediated by the vagus nerve on depression-like behaviors in rodent models, as well as human studies showing dysfunctions in neural substrates for interoception and reduced sensitivity to stimuli in depressed participants. Harshaw (2015) organises and interprets the findings from these studies and tries to incorporate the many potential pathways that result in interoceptive dysfunction, interoception’s relations with the likes of gender, individual, and cultural differences, and a developmental psychobiological systems perspective. The likely differential factors predisposing people to somatic and interoceptive dysfunction across their lifespan are presented. Although more research would be helpful, Harshaw (2015) mentions that the “current theory and evidence” suggests a disturbance of the interoceptive-exteroceptive integration may be the cause of the core symptoms of depression. [NPID: interoception, interoceptive awareness, somatic, depression, somatic signaling, vagus nerve, animal, animal studies]

This 2019 study assessed the involvement of the anterior insular cortex (AIC), which mediates interoceptive attention (attention towards physiological signals arising from the body), in interoceptive attention in healthy subjects. The necessity of the AIC in interoceptive attention was also tested by recruiting patients with AIC lesions. Interoceptive attention was determined by using functional magnetic resonance imaging while a novel task was employed - one that directs attention towards breathing rhythm. The results indicated interoceptive attention was associated with increased activation of the AIC. Moreover, the enhanced coupling between the AIC and somatosensory areas, as well as the reduced coupling between the AIC and visual sensory areas were observed. AIC activation was predictive of individual differences in interoceptive accuracy. Importantly, the study found that interoceptive accuracy and sensitivity was disrupted in patients with AIC lesions, providing compelling evidence that the AIC indeed plays a critical role in interoceptive attention.[NPID: interoception, interoceptive awareness, insula, anterior insular cortex, AIC, interoceptive attention, insula lesions, breathing rhythm, interoceptive accuracy]

This 2013 review’s focal point was the involvement of the insula (part of the cerebral cortex that integrates perception, emotion, interoceptive awareness, cognition, and gustation) in food processing and on multimodal integration of food-related items. Influencing factors of insular activation elicited by various foods range from calorie content to the internal physiologic state, body mass index or eating behavior. Also the anterior and mid-dorsal section of the insular cortex was more activated upon by sensory perception of food-related stimuli like smelling, seeing, and tasting. Apart from the pure sensory gustatory processing, there is also a strong association with the rewarding/hedonic aspects of food items, which is reflected in higher insular activity and stronger connections to other reward-related areas. One of the findings was that the processing of food items elicit different insular activation in lean compared to obese subjects and in patients suffering from an eating disorder (anorexia nervosa (AN), bulimia nervosa (BN)). These functional differences in the insular cortex could potentially be exploited to design non-invasive treatment approaches for eating disorders and for obesity. The authors suggested real-time magnetic resonance imaging neurofeedback as a means to target brain functions directly and to learn to control the anterior insular cortex activity voluntarily. First evidence demonstrated that obese adults have an enhanced ability to regulate the anterior insular cortex. [NPID: interoception, interoceptive awareness, insula, emotion, cognition, gustation, reward, eating disorders, obesity]

Wu et. al (2020) studied the anterior insular cortex (aIC) which integrates interoceptive states and emotional awareness and consequently guides behavioral responses. This experiment on mice demonstrated that the right side aIC CamKII+ (aICCamKII) neurons, when hyperactivated, attenuated food consumption, whereas in the case that they are inhibited feeding increases and the anorexia and weight loss induced initially by neural activation was reversed. Similar manipulation at the left-side aIC did not cause significant behavioral changes. The reason appears to be that aICCamKII neurons project directly to the vGluT2+ neurons in the lateral hypothalamus (LH) while the right-side aICCamKII-to-LH pathway mediates feeding suppression. This study revealed the existence of a circuit from the cortex to the hypothalamus that senses aversive (causing strong dislike) visceral signals and controls feeding behavior. [NPID: interoception, interoceptive awareness, emotional awareness, eating disorders, hypothalamus, visceral signals]

This 2019 study recruited 45 college students with varying body mass indexes to investigate the dynamic interactions among three neural systems (impulsive system; reflective system; and homeostasis sensing system) that are implicated in substance and behavioral addictions in response to food cues. Functional magnetic resonance imaging data were acquired while participants performed food-related Go/NoGo tasks, with low-calorie and high-calorie food cues. The scans were taken under both food satiety and deprivation conditions. The results showed that the subjects found it difficult to not respond to high-calorie foods, especially during the food deprivation condition. The neural activity of the insula and of the striatum increased bilaterally in response to high-calorie foods during Go trials while neurons in the anterior cingulate cortex and dorsolateral prefrontal cortex became more activated during NoGo trials. Dynamic causal modeling analysis revealed that food deprivation modulated the communications between the insula, striatum, and dorsolateral prefrontal cortex, and the modulations were positively associated with body mass index. The study suggests that the deprivation states such as hunger trigger insular activity which then modulates the balance between impulsive and reflective systems when facing temping food cues. [NPID: interoception, interoceptive awareness, impulsiveness, reflection, behavioral addictions, food cues, satiety, insula, striatum, dorsolateral prefrontal cortex, temptation]

Relationship between dispositional mindfulness, psychological health, and diet quality among healthy midlife adults

Getting to the heart of the matter: Does aberrant interoceptive processing contribute towards emotional eating?

Difficulties in emotion regulation and deficits in interoceptive awareness in moderate and severe obesity

Interoceptive reliance as a major determinant of emotional eating in adult obesity