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    Modulating interoception by insula stimulation: A double-blinded tDCS study
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    Abstract Interoception plays an important role in emotion processing, but the relationship between the physiological responses associated with emotional experience and interoception is unclear. In this study, we measured interoceptive sensitivity using the heartbeat discrimination task and investigated the effects of individual differences in interoceptive sensitivity on changes in heart rate and insula activity in response to music-induced emotions. We found that the heart rate increased when listening to the music pieces rated as emotionally high-touching in the high interoceptive sensitivity group only. Compared to the emotionally low-touching music, listening to the emotionally high-touching music was associated with higher insula activity. Furthermore, relative to individuals with low interoceptive sensitivity, the region of interest analysis of the insula subregions for individuals with high interoceptive sensitivity revealed significant activity in the bilateral dorsal granular insula, the right ventral dysgranular insula, and the right granular and dorsal dysgranular insula while listening to the high-touching music pieces. Our results suggest that individuals with high interoceptive sensitivity use their physical condition to assess their emotional level when listening to music. Furthermore, the insula activity may reflect the use of interoception to estimate emotions.
    Interoception
    Heart beat
    Citations (1)
    Transcranial electrical stimulation (tES) is a non-invasive brain stimulation method that has evoked increasing interest during the past years. The most common form of tES, transcranial direct current stimulation (tDCS), is considered to modulate neuronal resting potentials. For example, anodal stimulation over motor cortex appears to lead to increased neuronal excitability under the stimulation electrodes. However, some recent findings suggest that the effects of tDCS extend beyond the cortical areas under the electrodes, to deeper brain structures such as the midbrain. The brain also actively regulates peripheral physiology. Thus, changes in brain activity following tES may lead to modulation of peripheral physiology. For example, tDCS targeting primary motor cortex has been observed to induce changes in peripheral glucose metabolism. Furthermore, stimulation of dorsolateral prefrontal cortex has been shown to lead to alterations in cortisol secretion and the activity of the autonomic nervous system. Unpublished findings from our group corroborate with the above observations. Nevertheless, the evidence regarding peripheral effects of tES remains limited. Investigating such possible effects may be relevant especially from the point of view of tES safety and potential therapeutic discoveries. Disclosure of interest The author has not supplied his declaration of competing interest.
    Transcranial Direct Current Stimulation
    Brain stimulation
    Electrical brain stimulation
    Interoceptive signals, such as the heartbeat, are processed in a network of brain regions including the insular cortex. Recent studies have shown that such signals modulate perceptual and cognitive processing, and that they impact visual awareness. For example, visual stimuli presented synchronously to the heartbeat take longer to enter visual awareness than the same stimuli presented asynchronously to the heartbeat, and this is reflected in anterior insular activation. This finding demonstrated a link between the processing of interoceptive and exteroceptive signals as well as visual awareness in the insular cortex. The advantage for visual stimuli which are asynchronous to the heartbeat to enter visual consciousness may indicate a role for the anterior insula in the suppression of the sensory consequences of cardiac signals. Here, we present data from the detailed investigation of two patients with insular lesions (as well as four patients with non-insular lesions and healthy age matched controls) indicating that a lesion of the anterior insular cortex, but not of other regions, abolished this cardio-visual suppression effect. The present data provide causal evidence for the role of the anterior insula in the integration of internal interoceptive and external sensory signals for visual awareness.
    Insular cortex
    Heart beat
    Interoception
    Citations (0)
    Abstract Brain stimulation with weak electrical currents (transcranial electrical stimulation, tES) is known already for about 60 years as a technique to generate modifications of cortical excitability and activity. Originally established in animal models, it was developed as a noninvasive brain stimulation tool about 20 years ago for application in humans. Stimulation with direct currents (transcranial direct current stimulation, tDCS) induces acute cortical excitability alterations, as well as neuroplastic after-effects, whereas stimulation with alternating currents (transcranial alternating current stimulation, tACS) affects primarily oscillatory brain activity but has also been shown to induce neuroplasticity effects. Beyond their respective regional effects, both stimulation techniques have also an impact on cerebral networks. Transcranial magnetic stimulation (TMS) has been pivotal to helping reveal the physiological effects and mechanisms of action of both stimulation techniques for motor cortex application, but also for stimulation of other areas. This chapter will supply the reader with an overview about the effects of tES on human brain physiology, as revealed by TMS.
    Transcranial Direct Current Stimulation
    Brain stimulation
    Electrical brain stimulation
    Abstract Interoception refers to the perception of the internal bodily states. Recent accounts highlight the role of the insula in both interoception and the subjective experience of anxiety. The current study aimed to delve deeper into the neural correlates of cardiac interoception; more specifically, the relationship between interoception-related insular activity, interoceptive accuracy, and anxiety. This was done using functional magnetic resonance imaging (fMRI) in an experimental design in which 40 healthy volunteers focused on their heartbeat and anxious events. Interoceptive accuracy and anxiety levels were measured using the Heartbeat Perception Task and State Trait Anxiety Inventory, respectively. The results showed posterior, mid and anterior insular activity during cardiac interoception, whereas anxiety-related activation showed only anterior insular activity. Activation of the anterior insula when focused on cardiac interoception was positively correlated to state and trait anxiety levels, respectively. Moreover, the mid-insular activity during the cardiac attention condition not only related to individuals’ interoceptive accuracy but also to their levels of state and trait anxiety, respectively. These findings confirm that there are distinct neural representations of heartbeat attention and anxious experience across the insular regions, and suggest the mid-insula as a crucial link between cardiac interoception and anxiety.
    Interoception
    Heart beat
    Insular cortex
    Citations (58)
    Interoception – the processing of the physiological states of the entire body, communicated to the brain and integrated to influence behaviour - has been a an area of interest in various domains. Previous research using a behavioural measure of interoception demonstrated higher interoceptive accuracy in musicians in comparison to non-musicians. The present study extends this research by comparing additional measures of interoception between the two groups. In addition to the previously assessed heartbeat discrimination task, we used the heartbeat tracking task to measure interoceptive accuracy (IAcc). We also tested two sub-scales from the multidimensional assessment of interoceptive awareness questionnaire to measure interoceptive sensibility (IS). Another measure we recorded was an electrophysiological index of interoceptive processing - the heartbeat evoked potential (HEP). The participants comprised musicians (N = 20) and age-matched non-musicians (N = 20). We predicted that musicians would have higher IAcc and IS, and would show a greater HEP amplitude than non-musicians. Results showed that musicians had higher IAcc and IS scores than non-musicians and they showed larger HEP amplitude (in the left hemisphere only). This is the first demonstration of enhanced neural processing of interoceptive signals and interoceptive sensibility in musicians. We suggest that these differences may relate to alterations to insula connectivity as a result of musical training.
    Interoception
    Heart beat
    Citations (4)