The role of the Somatosensory System in the generation and perception of emotions: a transcranial Alternated Current Stimulation (tACS) study

Emotional experiences have a deep impact on our bodily states, such as when we feel ‘fear’ our body feels cold and unable to move, and when we feel ‘anger’ we close our fists and feel our face burning. Recent behavioural studies have shown that emotions can be mapped onto specific body portions, suggesting that emotions are represented in the somatosensory system. However, what is the role of the somatosensory system in the processing of emotions and, more specifically, in the generation of feelings of emotions? To answer this question, we applied transcranial alternated current stimulation (tACS) to the somatosensory cortex of healthy adult participants at different frequencies while they saw emotional pictures taken from the IAPS database. We found that modulation of cortical excitability of S1 influenced subjective emotional ratings, particularly affecting Valence, and making the participants rating more pleasant, instead, we didn’t find a clear effect on Arousal (measured through the skin conductance response). Our results suggest a dissociation between the two dimensions of emotions: Arousal and Valence, with the latest being the only one affected by tACS applied on S1 at different frequencies. This is compatible with previous studies suggesting different neural substrates for Valence and Arousal, in which the Orbitofrontal cortex process valance and the amygdala preferentially process arousal. In general, our findings suggest that the somatosensory system plays a crucial role in the generation of emotions

Visual perceptual learning is enhanced by training in the illusory far space

Visual objects in the peripersonal space (PPS), are perceived faster than farther ones, appearing in the extrapersonal space (EPS). This shows preferential processing for visual stimuli near our body. Such an advantage should favor visual perceptual learning occurring near, as compared to far from observers, but opposite evidence has been recently provided from online testing protocols, showing larger perceptual learning in the far space. Here, we ran two laboratory-based experiments investigating whether visual training in PPS and EPS has different effects. We used the horizontal Ponzo Illusion to create a lateralized depth perspective while participants completed a visual search task in which they reported whether or not a specific target object orientation (e.g., a triangle pointing upward) was present amongst distractors. This task was completed before and after a training phase in either the (illusory) near or far space for one hour. In Experiment 1, the near space was in the left hemispace, whereas in Experiment 2 it was in the right. Results showed that, in both experiments, participants were more accurate after training in the far space, whereas training in the near space led to either improvement in the far space (Exp. 1), or no change (Exp. 2). Moreover, we found a larger visual perceptual learning when stimuli were presented in the left compared to the right hemispace. Differently from visual processing, visual perceptual learning is more effective in the far space. We propose that depth is a key dimension that can be used to improve human visual learning

The role of the somatosensory system in the processing of emotions: a transcranial alternated stimulation (tACS) study

Emotional experiences have a deep impact on our bodily states, such as when we feel ‘fear’ our body feels cold and unable to move, and when we feel ‘anger’ we close our fists and feel our face burning. Recent behavioural studies have shown that emotions can be mapped onto specific body portions, suggesting that emotions are represented in the somatosensory system. However, what is the role of the somatosensory system in the processing of emotions and, more specifically, in the generation of feelings of emotions? To answer this question, we applied transcranial alternated current stimulation (tACS) to the somatosensory cortex of healthy adult participants at different frequencies while they saw emotional pictures taken from the IAPS database. We found that modulation of cortical excitability of S1 influenced subjective emotional ratings, particularly affecting Valence, and making the participants rating more pleasant, instead, we didn’t find a clear effect on Arousal (measured through the skin conductance response). Our results suggest a dissociation between the two dimensions of emotions: Arousal and Valence, with the latest being the only one affected by tACS applied on S1 at different frequencies. This is compatible with previous studies suggesting different neural substrates for Valence and Arousal, in which the Orbitofrontal cortex process valance and the amygdala preferentially process arousal. In general, our findings suggest that the somatosensory system plays a crucial role in the generation of emotions

Visual perceptual learning is enhanced by training in the illusory far space

Visual objects in the peripersonal space (PPS), are perceived faster than farther ones, appearing in the extrapersonal space (EPS). This shows preferential processing for visual stimuli near our body. Such an advantage should favor visual perceptual learning occurring near, as compared to far from observers, but opposite evidence has been recently provided from online testing protocols, showing larger perceptual learning in the far space. Here, we ran two laboratory-based experiments investigating whether visual training in PPS and EPS has different effects. We used the horizontal Ponzo Illusion to create a lateralized depth perspective while participants completed a visual search task in which they reported whether or not a specific target object orientation (e.g., a triangle pointing upward) was present amongst distractors. This task was completed before and after a training phase in either the (illusory) near or far space for one hour. In Experiment 1, the near space was in the left hemispace, whereas in Experiment 2 it was in the right. Results showed that, in both experiments, participants were more accurate after training in the far space, whereas training in the near space led to either improvement in the far space (Exp. 1), or no change (Exp. 2). Moreover, we found a larger visual perceptual learning when stimuli were presented in the left compared to the right hemispace. Differently from visual processing, visual perceptual learning is more effective in the far space. We propose that depth is a key dimension that can be used to improve human visual learning

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 cortex (S1) in emotion processing. However, the causal role of S1 in emotion generation remains unclear. To address this question, we applied transcranial Alternating Current Stimulation (tACS) on S1 at different frequencies (beta, theta and sham) while participants saw emotional stimuli with different degrees of pleasantness and level of arousal. Results showed that modulation of S1 influenced subjective emotional ratings as a function of the frequency applied. While beta-tACS made participants rate the emotional images as more pleasant (higher valence), theta-tACS lowered the subjective arousal ratings (more calming). Skin conductance responses confirmed a different arousal for pleasant vs 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

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 S1 at different frequencies (beta, theta and sham) while participants saw emotional stimuli with different degrees of pleasantness and level 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, only theta-tACS lowered the subjective arousal ratings. Skin conductance responses confirmed a different arousal for pleasant vs 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