The role of the somatosensory system in the feeling of emotions: a neurostimulation study.

Emotional experiences deeply impact our bodily states, such as when we feel 'anger', our fists close and our face burns. Recent studies have shown that emotions can be mapped onto specific body areas, suggesting a possible role of the primary somatosensory system (S1) in emotion processing. To date, however, the causal role of S1 in emotion generation remains unclear. To address this question, we applied transcranial alternating current stimulation (tACS) on the S1 at different frequencies (beta, theta, and sham) while participants saw emotional stimuli with different degrees of pleasantness and levels of arousal. Results showed that modulation of S1 influenced subjective emotional ratings as a function of the frequency applied. While theta and beta-tACS made participants rate the emotional images as more pleasant (higher valence), only theta-tACS lowered the subjective arousal ratings (more calming). Skin conductance responses recorded throughout the experiment confirmed a different arousal for pleasant versus unpleasant stimuli. Our study revealed that S1 has a causal role in the feeling of emotions, adding new insight into the embodied nature of emotions. Importantly, we provided causal evidence that beta and theta frequencies contribute differently to the modulation of two dimensions of emotions-arousal and valence-corroborating the view of a dissociation between these two dimensions of emotions.

Mapping the emotional homunculus with fMRI.

Emotions are commonly associated with bodily sensations, e.g., boiling with anger when overwhelmed with rage. Studies have shown that emotions are related to specific body parts, suggesting that somatotopically organized cortical regions that commonly respond to somatosensory and motor experiences might be involved in the generation of emotions. We used functional magnetic resonance imaging to investigate whether the subjective feelings of emotion are accompanied by the activation of somatotopically defined sensorimotor brain regions, thus aiming to reconstruct an "emotional homunculus." By defining the convergence of the brain activation patterns evoked by self-generated emotions during scanning onto a sensorimotor map created on participants' tactile and motor brain activity, we showed that all the evoked emotions activated parts of this sensorimotor map, yet with considerable overlap among different emotions. Although we could not find a highly specific segmentation of discrete emotions over sensorimotor regions, our results support an embodied experience of emotions.

The emergence of the multisensory brain: From the womb to the first steps.

The becoming of the human being is a multisensory process that starts in the womb. By integrating spontaneous neuronal activity with inputs from the external world, the developing brain learns to make sense of itself through multiple sensory experiences. Over the past ten years, advances in neuroimaging and electrophysiological techniques have allowed the exploration of the neural correlates of multisensory processing in the newborn and infant brain, thus adding an important piece of information to behavioral evidence of early sensitivity to multisensory events. Here, we review recent behavioral and neuroimaging findings to document the origins and early development of multisensory processing, particularly showing that the human brain appears naturally tuned to multisensory events at birth, which requires multisensory experience to fully mature. We conclude the review by highlighting the potential uses and benefits of multisensory interventions in promoting healthy development by discussing emerging studies in preterm infants.

Touch me or touch me not: Emotion regulation by affective touch in human adults.

In mammals, including humans, affective touch (AT) supports the establishment and maintenance of social connections and mitigates the effects of social conflict and ostracism. AT is used to describe slowly moving, low-forced mechanical stimulation that is frequently perceived as pleasant. In humans, AT has been addressed particularly for its role in promoting bonding and emotional regulation during early development; however, more recent studies have suggested that AT also preserves physical and emotional well-being in adulthood. Here, we investigated whether AT can buffer adults' experience of negative emotions as reflected in their behavioral and physiological responses to emotionally arousing stimuli. Participants were stimulated on their forearms using AT or tapping (T) while they viewed a series of emotionally arousing and neutral images, and we measured their skin conductance response and their explicit rating of the images' unpleasantness. We found that AT, but not T, reduced the arousal and perceived unpleasantness of the emotional stimuli but not the neutral ones, revealing the soothing role of AT in emotional contexts. The second aim of the study was to explore the possibility that AT might benefit some individuals more than others, according to their individual differences. To this aim, we assessed individuals' empathy and sensory processing sensitivity, as well as their perception of AT itself. Results revealed that while empathy did not predict changes in emotional processing irrespective of tactile stimulation, individuals with higher sensitivity reported AT as less pleasant. We discuss the possible factors mediating the observed interindividual variability in AT perception. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Embodied language of emotions: Predicting human intuitions with linguistic distributions in blind and sighted individuals.

Recent constructionist theories have suggested that language and sensory experience play a crucial role not only in how individuals categorise emotions but also in how they experience and shape them, helping to acquire abstract concepts that are used to make sense of bodily perceptions associated with specific emotions. Here, we aimed to investigate the role of sensory experience in conceptualising bodily felt emotions by asking 126 Italian blind participants to freely recall in which part of the body they commonly feel specific emotions (N = 15). Participants varied concerning visual experience in terms of blindness onset (i.e., congenital vs late) and degree of visual experience (i.e., total vs partial sensory loss). Using an Italian semantic model to estimate to what extent discrete emotions are associated with body parts in language experience, we found that all participants' reports correlated with the model predictions. Interestingly, blind - and especially congenitally blind - participants' responses were more strongly correlated with the model, suggesting that language might be one of the possible compensative mechanisms for the lack of visual feedback in constructing bodily felt emotions. Our findings present theoretical implications for the study of emotions, as well as potential real-world applications for blind individuals, by revealing, on the one hand, that vision plays an essential role in the construction of felt emotions and the way we talk about our related bodily (emotional) experiences. On the other hand, evidence that blind individuals rely more strongly on linguistic cues suggests that vision is a strong cue to acquire emotional information from the surrounding world, influencing how we experience emotions. While our findings do not suggest that blind individuals experience emotions in an atypical and dysfunctional way, they nonetheless support the view that promoting the use of non-visual emotional signs and body language since early on might help the blind child to develop a good emotional awareness as well as good emotion regulation abilities.