Lecture 5 - Insula Cortex and Interoception PDF

Lecture 5 - Insula Cortex and Interoception Overview Interoception: definitions, relevance, historical context Measures of interoception Heart beat counting Gastric interoception Neural basis The insula Interoception & emotion Alexithymi...

Lecture 5 - Insula Cortex and Interoception Overview Interoception: definitions, relevance, historical context Measures of interoception Heart beat counting Gastric interoception Neural basis The insula Interoception & emotion Alexithymia and social cognition in autism Emotion recognition and empathy interoception and self/ agency Von Economo Neurons What is Interoception? Interoception is the perception of one’s physiological condition, encompassing pain, temperature, itch, touch, muscular and visceral sensations, vasomotor activity (regulation of blood flow in small blood vessels) and hunger Refers to the representation of the internal states of an organism, and includes the processes by which it senses, interprets, integrates, and regulates signals from within itself Interoception refers to the process by which the nervous system senses, interprets and integrates signals originating from within the body, providing a moment-by-moment mapping of the body’s internal landscapr across conscious and unconscious levels Why is interoception important? interoception signalling has been considered a component process of reflexes, urges, feelings, drives, adaptive responses, and cognitive and emotional experiences, highlighting its contributions to the maintenance of homeostatic functioning, body regulation and survival Interoception also plays an integral role in emotional experience, self-regulation, decision making and consciousness Dysfunction of interoception is increasingly recognised as an important component of different mental health conditions, including anxiety disorders, mood disorders, eating disorders, addictive disorders, and somatic symptom disorders The role of the body in emotion The James-Lange theory of emotion William James (1884) and Carl lange (1887) proposed the same theory that is now called the James-Lange theory of emotion Emotions are the result of our perception/ interpretation of bodily reactions elicited by a stimulus Interoceptive ability is relevant to such ‘peripheral’ theories of emotion Interation between facial expression and experience of emotion “The free expression by outward signs of an emotion intensifies it… the repression, as far as this is possible, of all outward signs softens our emotions” - Charles Darwin “Refuse to express a passion, and it dies” - William James ** The facial feedback hypothesis ** Facial muscle activation sends (feedback) signals to the brain Facial feedback impacts Our feelings Our perception of others The Somatic Marker Hypothesis Efficient decision-making requires emotion Emotion and feelings create ‘somatic markers’ Feelings in the body that are associated with emotions, such as the association of rapid heartbeat with anxiety or of nausea with disgust Somatic markers act as signals to guide behaviour Measuring Interoception Self-report questionnaires Multidimensional Assessment of Interoceptive Awareness (MAIA) Objective Measures Heartbeat counting task Most common measure of interoceptive accuracy 2 versions: Heartbeat tracking: silently count number of heartbeats in a time window vs number of actual heartbeats Heartbeat discrimination: report the timing of individual heartbeats, through tapping or through perceived synchrony of the heartbeats with external stimuli Control Participants’ ability to estimate time intervals of varying duration Interoceptive awareness: confidence in interoceptive accuracy The Baroeflex A homeostatic mechanism that helps to maintain blood pressure at nearly constant levels Provides a rapid negative feedback loop in which an elevated blood pressure causes the heart rate to decrease Baroreceptor signalling changes with eery heartbeat Blood pressure goes slightly up with every contraction of the heart This information about when and how strong the heart is beating does not only reach the brainstem It also travel up the neural axis and informs other parts of the brain, including the limbic and cortical regions Interoception & Emotion in the Insula Insula is buried inside the lateral sulcus The question of the role of bodily sensations in emotion has been debated for over 100 years Craig (2009) suggests that this extends to “all subjective feeling states” Sequential integration of homeostatic conditions with the sensory environment and motivation and social conditions, culminating in a ‘global emotional moment’ Hear a sound for each heartbeat HEART condition: indicate if sound was in time with own heartbeat or not NOTE condition: to listen out for a deviant sound  increased grey matter volume in right anterior insula correlated with heartbeat discrimination performance  ^ Fresh blood is pumped into the Aorta People scoring high in state anxiety show less inhibition of threat processing at diastole (which might contribute to sustained overreacting to fear signal and threat in anxiety). Injected isoproterenol, a sympathetic (beta adrenergic) agonist similar to adrenaline This increases sympathetic arousal and the conscious experience of cardiorespiratory  sensations Gastric Interoception stomach contracts every ~20 seconds (0.05 Hz) contraction frequency controlled by cells in the stomach wall contraction amplitude controlled by the CNS The brain is continuously informed about the gastric cycle through the vagus nerve (as well as a spinothalamic pathway) Gastric signals reach multiple cortical and subcortical areas (including the insula) N = 15 women with restricting-type AN N = 15 controls Task: attend to stomach, heart, bladder for 10 sec People with AN had reduced activation in dorsal mid-insula when attending to sensations from their stomach ** So is the insula necessary for interoception? ** ** And does insula activation necessarily mean interoception? ** 1 patient (Roger) with bilateral insula and ACC damage + 11 age-matched controls Injections of up to 4mg of isoproterenol (~adrenaline) After each injection, participants report heartbeat sensations with a dial Anesthetic skin cream applied to the chest There are 2 ways to feel your heartbeat: 1. baroreceptors and insula/ACC 2. the skin of the chest, presumably involving SI and SII, Careful with reverse inference The insular cortex shows up in ~1/3 of fMRI studies which is sometimes abused to claim all sorts of things Alexithymia and Social Cognition in Autism Individuals with autism aften have problems with social cognition A number of recent papers have suggested that these problems may sten from comorbid Alexithymia (5% prevalence in the normal population, 50% in autism) Alexithymia A subclinical inability to identify emotions in the self Toronto Alexithymia Scale: "I am often confused about what emotion I am feeling." "I am often puzzled by sensations in my body." "I often don’t know why I am angry." 15 adults with autism and 15 controls. Alexithymia Questionnaires (TAS-20; BVAQ-B). Empathy Questionnaire (IRI; Interpersonal reactivity index). measured brain activity during a task requiring participants to introspect on their emotion.  Controls showed a bigger difference in Insula activity between the emotion and colour balance task. This effect was largely explained by Alexithymia, which correlated with this activation for both groups (the groups differed on Alexithymia).  Activity in anterior insula during emotion task was positively correlated with empathy, and negatively correlated with Alexithymia. Empathy –ly correlated with Alexithymia. Alexithymia and Autism Alexithymia is associated with reduced activity in insular cortex (interoceptive cortex). Individuals with autism have a higher prevalence of alexithymia than those in the general population. Alexithymia is associated with reduced empathy. Empathy for Pain Painful electrical stimulation applied to you, or a loved-one in the same room. Visual Cues to symbolise pain or non-pain to you or partner.  Used the same paradigm as Singer et al. (2004), with 18 autistic adults and 18 Alexithymia matched controls. Electrical stimulation applied to self or partner (as many of the autistic participants were not in a romantic relationship, this was often a family member) Activity in insula cortex for other pain – other no pain was inversely with alexithymia, independent of diagnosis of autism Alexithymia, Empathy and Autism Alexithymia, not autism, predicts insular cortex activity during empathy for pain. –Alexithymia is associated with reduced activity in insular cortex during empathy for pain. This fits with the suggestion that insular cortex is crucial for understanding our own feeling states (including pain), and therefore also other people’s feeling states. Alexithymia, Autism and Emotion Recognition Stimuli show morphing of emotion and identity At the end of each trial, participants are asked to categorise either the emotion or identity Regression analyses revealed that alexithymia, and not autism, predicted expression attribution precision. This study shows that deficits in emotion recognition, often associated with autism, are actually caused by co-occurring Alexithymia. people who have difficulties understanding their own emotions, also have problems interpreting other people’s emotions. The studies discussed so far suggest that Alexithymia may be a cause of emotion-related differences in autism. But does this explain all different aspects of autism? –What about cognitive empathy / theory of mind?  Interoceptive accuracy was assessed with the heartbeat tracking task Participants then completed the Movie for the Assessment of Social Cognition (MASC), a measure of ToM –watch a social event in which accurate mental state inferences are needed to understand the story The Movie for the Assessment of Social Cognition (MASC) is a sensitive video-based test for the evaluation of subtle mindreading difficulties. It requires study subjects to watch a 15 min movie (divided in short clips) about four characters getting together for a dinner party. After viewing each clip, participants are presented with a multiple choice question requiring them to infer the mental state of one character. Performance is quantified separately for emotional (e.g., “What is Sandra feeling?”) and non- emotional (e.g., “What is Michael thinking?”) questions.  Interoceptive accuracy was positively correlated with overall MASC score, driven by a significant association between interoception and emotional items. there was no such association between interoception and the non-emotional items Mid Summary Alexithymia seems to be associated with differences in emotion recognition and empathy, but might not be related to differences in ToM. –Thinking back to other lectures: insula cortex was prevalent in research on empathy, but not theory of mind. This is consistent with the idea that insular cortex generates subjective feelings or global emotional moments through the re-representation of interoceptive signals. ASC indeed showed reduced covariance in networks centered on dmPFC and TPJ, but not within fronto-insular (FI) networks. Irrespective of ASC, covariance was negatively modulated by alexithymia in networks extending from FI to posterior regions. Interoception and Self/Agency The insula in sense of agency and body ownership Anterior Insula: Greater activity in self agency. The AI might be concerned with the integration of all the concordant multimodal sensory signals associated with voluntary movements Farrer & Frith (2002) Participants used a joystick to move a ball through a t-maze. They were told that on some trials the experimenter would control the ball and not them. Greater activation of angular gyrus in other-attribution condition. In the self-attribution condition, they had greater activation of the anterior insula (left and right). This suggests that this part of the brain is important for our experience of agency. Rubber Hand Illusion (RHI) The intensity of the RHI (amount of proprioceptive drift) related to activity in the posterior insula Patients who exhibit disturbed sense of limb ownership (DSO) typically show damage to insular cortex. RHI modulated by interoceptive accuracy  Participants with high interoceptive sensitivity showed a reduced rubber hand illusion. These people may be particularly attuned to their own body and therefore are less easily tricked into taking ownership of a rubber hand. This suggests that interoception, processed in insula cortex, is important in the maintaining body ownership (your sense of bodily self). Full body illusion and interoception When the other body flashes in time with your heart you are more likely to take ownership of the virtual body. Summary: Interoception, Insula, Self, and Agency Insula cortex activity associated with the degree of body illusions Insula damage results in disturbed sense of limb ownership Individual differences in interoceptive accuracy predict susceptibility to body illusions Consistency between exteroceptive information and interoceptive information increases body  illusions This suggests that recognition of our body relies on combining interoceptive signals with other sensory information Von Economo Neurons Many tasks show activation of both AIC and ACC.  Consistent with afferent connections from the body. Von Economo neurons (spindle neurons) only exist in these areas of the brain. “Selective destruction of VENs in early stages of fronto-temporal dementia implies that they are involved in empathy, social awareness, and self-control, consistent with evidence from functional imaging.” Summary Von Economo Neurons Von Economo Neurons (VENs) might provide higher transmission speed They are only present in Insula and ACC, and only in humans, some great apes, and some other mammal species (whales and dolphins) These animals are the only ones to show some form of self-awareness Therefore, VENs are thought to be crucial for interoception, and aspects of consciousness, but also emotion understanding, empathy, ToM, social awareness, and self-control Anomalies of VENs possible cause of several neurological and mental health disorders Overall Summary Insular cortex is important for emotion recognition, empathy, self-awareness, agency. This is likely due to the importance of this region in processing interoceptive signals (which matter for homeostasis) The past 20 – 30 years has seen a sharp increase in the interest for understanding interoception and its neural bases, largely fueled by the recognition that anomalies in interoception occur in many neurodevelopmental and neuropsychiatric disorders  Is interoception a unified system (as the visual, or the auditory system) or should it be decomposed by organs or functions? What is the developmental trajectory of interoception? Is there maternal interoception of the foetus? What is the link between interoception and emotion? What is the link between interoception and the self? How does interoception influence exteroception, and conversely? What are the boundaries of interoception - are they determined anatomically, functionally? What is the link between interoception and chronic diseases, like cancer? #PS495