Right Hemisphere Dominance for Unconscious Emotionally Salient Stimuli

Does the right hemisphere retain functional characteristics typical of the emotional adaptive system? An evolutionary approach to the problem of brain asymmetries

The right and left hemispheres host two complementary adaptive systems with a right-sided prevalence of automatic and unconscious processing modes, typical of the 'emotional system', and a left-sided prevalence of propositional and conscious processing modes typical of the 'cognitive system' The principal right hemispheric syndromes (and the functioning modes typical of this hemisphere) are, indeed, characterized by automatic and unconscious processing modalities. Thus, the unilateral neglect syndrome discloses a defective automatic (and spared intentional) spatial orienting of attention; face and voice recognition disorders are due to disruption of mechanisms that automatically generate familiarity feelings and anosognosia seems due to the unconscious loss of personal significance attributed by the patient to the pathological event. Since emotions were the only adaptive system existing before the development of language (which is provided of a strong capacity to develop and shape cognition), the persistence in the right hemisphere of mechanisms typical of the emotional system strongly supports an evolutionary model of brain laterality. (160 words).

A historical approach to models of emotional laterality

In this paper I discuss the main models that have tried to explain brain asymmetries for emotions. The first models, based on clinical observations, proposed either a general right hemisphere dominance for emotions (the'right hemisphere') model or a different specialization of the right hemisphere for negative and of the left hemisphere for positive emotions (the'valence' model). In more recent times new models, based on partly modified versions of the previous ones have been proposed. The revised version of the 'valence' model, labeled the 'approach-avoidance' model maintained that hemispheric asymmetries are not related to the valence of the emotional stimulus but to the motivational (approach vs avoidance) system that is engaged by that stimulus. On the contrary, revised versions of the 'right hemisphere' hypothesis proposed graded versions of this model, maintaining that only some kinds or some levels of emotions are clearly right lateralized. One version of these models (the'emotion type hypothesis') assumed that only elementary basic emotions should be subsumed by the right hemisphere, wheres more complex social emotions should be subtended by the left hemisphere. The other version (the 'schematic level of emotion hypothesis') assumed that the right hemisphere should subsume only the basic 'schematic' level of emotions, characterized by an automatic and unconscious processing, whereas the more propositional and conscious 'conceptual' level could be less lateralized or subsumed by the left hemisphere. This last model is supported by the obsevation that the right hemisphere reveals a modus operandi (i.e. a prevalence of the 'automatic' over the 'intentional' and of the 'unconscious' over the 'conscious' functional processing) that is typical of the 'schematic level of emotions.

Motor-sensory biases are associated with cognitive and social abilities in humans

Across vertebrates, adaptive behaviors, like feeding and avoiding predators, are linked to lateralized brain function. The presence of the behavioral manifestations of these biases are associated with increased task success. Additionally, when an individual's direction of bias aligns with the majority of the population, it is linked to social advantages. However, it remains unclear if behavioral biases in humans correlate with the same advantages. This large-scale study (N = 313-1661, analyses dependent) examines whether the strength and alignment of behavioral biases associate with cognitive and social benefits respectively in humans. To remain aligned with the animal literature, we evaluate motor-sensory biases linked to motor-sequencing and emotion detection to assess lateralization. Results reveal that moderate hand lateralization is positively associated with task success and task success is, in turn, associated with language fluency, possibly representing a cascade effect. Additionally, like other vertebrates, the majority of our human sample possess a 'standard' laterality profile (right hand bias, left visual bias). A 'reversed' profile is rare by comparison, and associates higher self-reported social difficulties and increased rate of autism and/or attention deficit hyperactivity disorder. We highlight the importance of employing a comparative theoretical framing to illuminate how and why different laterization profiles associate with diverging social and cognitive phenotypes.

When "more for others, less for self" leads to co-benefits: A tri-MRI dyad-hyperscanning study

Unselfishness is admired, especially when collaborations between groups of various scales are urgently needed. However, its neural mechanisms remain elusive. In a tri-MRI dyad-hyperscanning experiment involving 26 groups, each containing 4 participants as two rotating pairs in a coordination game, we sought to achieve reciprocity, or "winning in turn by the two interacting players," as the precursor to unselfishness. Due to its critical role in social processing, the right temporal-parietal junction (rTPJ) was the seed for both time domain (connectivity) and frequency domain (i.e., coherence) analyses. For the former, negative connectivity between the rTPJ and the mentalizing network areas (e.g., the right inferior parietal lobule, rIPL) was identified, and such connectivity was further negatively correlated with the individual's final gain, supporting our task design that "rewarded" the reciprocal participants. For the latter, cerebral coherences of the rTPJs emerged between the interacting pairs (i.e., within-group interacting pairs), and the coupling between the rTPJ and the right superior temporal gyrus (rSTG) between the players who were not interacting with each other (i.e., within-group noninteracting pairs). These coherences reinforce the hypotheses that the rTPJ-rTPJ coupling tracks the collaboration processes and the rTPJ-rSTG coupling for the emergence of decontextualized shared meaning. Our results underpin two social roles (inferring others' behavior and interpreting social outcomes) subserved by the rTPJ-related network and highlight its interaction with other-self/other-concerning brain areas in reaching co-benefits among unselfish players.

Alteration of prefrontal cortex and its associations with emotional and cognitive dysfunctions in adolescent borderline personality disorder

The neurobiological mechanism of borderline personality disorder (BPD) in adolescents remains unclear. The study aimed to assess the alterations in neural activity within prefrontal cortex in adolescents with BPD and investigate the relationship of prefrontal activity with emotional regulation and cognitive function. This study enrolled 50 adolescents aged 12-17 years with BPD and 21 gender and age-matched healthy control (HC) participants. Study assessment for each participant included a brain resting-state functional MRI (rs-fMRI), clinical assessment questionnaires such as Borderline Personality Features Scale (BPFS), Difficulties in Emotion Regulation Scale (DERS), Ottawa Self-Injury Inventory and Childhood Trauma Questionnaire (CTQ) and cognitive testing with Stroop Color-Word Test (SCWT). Fractional amplitude of low-frequency fluctuations (fALFF) and seed-based functional connectivity (FC) were obtained from rs-fMRI analysis. Correlation analysis was also performed to evaluate the associations of the neuroimaging metrics such as fALFF and FC with clinical assessment questionnaire and cognitive testing scores. Adolescents with BPD showed increased fALFF values in the right inferior frontal gyrus and decreased activity in the left middle frontal gyrus as compared to the HC group (p < 0.05, cluster size ≥ 100, FWE correction). In adolescents with BPD, increased fALFF in the right inferior frontal gyrus was related to the BPFS (emotional dysregulation), DERS-F (lacking of emotional regulation strategies) and Ottawa Self-Injury Inventory-4 C scores (internal emotional regulation function of self-injurious behavior). The reduced fALFF in the left middle frontal gyrus was associated with the SCWT-A (reading characters) and the SCWT-B (reading color) scores. Additionally, the fALFF values in the left middle frontal gyrus and the right inferior frontal gyrus were related to the CTQ-D (emotional neglect) (p < 0.05). The left middle frontal gyrus exhibited increased FC with the right hippocampus, left inferior temporal gyrus and right inferior frontal gyrus (voxel p < 0.001, cluster p < 0.05, FWE correction). The increased FC between the left middle frontal gyrus and the right hippocampus was related to the SCWT-C (cognitive flexibility) score. We observed diverging changes in intrinsic brain activity in prefrontal cortex, and neural compensatory changes to maintain function in adolescents with BPD. In addition, decreased neural function was closely associated with emotional dysregulation, while increased neural function as indicated by brain activity and FC was associated with cognitive dysfunction. These results indicated that alterations of intrinsic brain activity may be one of the underlying neurobiological markers for clinical symptoms in adolescents with BPD.

Decoding neural patterns for the processing of fearful faces under different visual awareness conditions: A multivariate pattern analysis

Previous studies have provided mixed findings regarding the nonconscious processing of fearful faces. Here, we used multivariate pattern analysis on electroencephalography data from three backward masking experiments to examine the processing of fearful faces under different visual awareness conditions. Three groups of participants were shown pairs of face images presented very briefly (for 16 ms) or for sufficiently long (for 266 ms), and completed tasks where the faces were either relevant to the experimental task (Experiment 1) or not (Experiments 2 and 3). Three main decoding analyses were performed. First, in the visual awareness decoding, the visibility of the faces, and hence participants' awareness of them, was maximally decodable in three time windows: 158-168 ms, 235-260 ms and 400-600 ms where the earlier neural patterns were generalized to the later stage activity. Second, we found that the spatial location of a fearful face in the face pairs was decodable, however only when the faces were consciously seen and task-relevant. Finally, we successfully decoded distinct neural patterns associated with the fearful-face-present conditions, compared to the fearful-face-absent conditions, and these patterns were decodable during both short and long presentations of the faces. Together, our results suggest that, while the processing of the spatial location of fearful faces requires awareness and task-relevancy, the mere presence of fearful faces can be processed even when visual awareness is highly restricted.

Differential modulation on neural activity related to flankers during face processing: A visual crowding study

In this visual crowding study, we manipulated the perceivability of a central crowded face (a fearful or a neutral face) by varying the similarity between the central face and the surrounding flanker stimuli. We presented participants with pairs of visual clutters and recorded their electroencephalography during an emotion judgement task. In an upright flanker condition where both the central target face and flanker faces were upright faces, participants were less likely to report seeing the target face, and their P300 was weakened, compared to a scrambled flanker condition where scrambled face images were used as flankers. Additionally, at ∼ 120 ms post-stimulus, a posterior negativity was found for the upright compared to scrambled flanker condition, however only for fearful face targets. We concluded that early neural responses seem to be affected by the perceptual characteristics of both target and flanker stimuli whereas later-stage neural activity is associated with post-perceptual evaluation of the stimuli in this visual crowding paradigm.

Faces capture spatial attention only when we want them to: An inattentional blindness EEG study

Previous research on emotional face processing has shown that emotional faces such as fearful faces may be processed without visual awareness. However, evidence for nonconscious attention capture by fearful faces is limited. In fact, studies using sensory manipulation of awareness (e.g., backward masking paradigms) have shown that fearful faces do not attract attention during subliminal viewings nor when they were task-irrelevant. Here, we used a three-phase inattentional blindness paradigm and electroencephalography to examine whether faces (fearful and neutral) capture attention under different conditions of awareness and task-relevancy. We found that the electrophysiological marker for attention capture, the N2-posterior-contralateral (N2pc), was elicited by face stimuli only when participants were aware of the faces and when they were task-relevant (phase 3). When participants were unaware of the presence of faces (phase 1) or when the faces were irrelevant to the task (phase 2), no N2pc was observed. Together with our previous work, we concluded that fearful faces, or faces in general, do not attract attention unless we want them to.

Right brain-to-right brain psychotherapy: recent scientific and clinical advances

This article overviews my recent acceptance of a Lifetime Achievement Award from Sapienza University of Rome, in which I discussed three decades of my work on the right brain in development, psychopathogenesis, and psychotherapy. In the following, I offer current brain laterality and hemispheric asymmetry research indicating that right brain emotional and relational processes operate beneath conscious awareness not only in early human development, but over the lifespan. I discuss recent interdisciplinary studies on the central role of ultrarapid right brain-to-right brain intersubjective communications of face, voice, and gesture and the implicit regulation of emotion in nonverbal attachment dynamics. Special emphasis is on the fundamental psychobiological process of interpersonal synchrony, and on the evolutionary mechanism of attachment, the interactive regulation of biological synchrony within and between organisms. I then present some clinical applications, suggesting that effective therapeutic work with "primitive" nonverbal emotional attachment dynamics focuses not on conscious verbal insight but on the formation of an unconscious emotion-communicating and regulating bond within the therapeutic relationship. Lastly, I review recent hyperscanning research of the patient's and therapist's brains during a face-to-face, emotionally focused psychotherapy session that supports the right brain-to-right brain communication model. I end suggesting that the right brain is dominant in both short-term symptom-reducing and long-term growth-promoting deep psychotherapy.

Subliminal Emotional Faces Elicit Predominantly Right-Lateralized Amygdala Activation: A Systematic Meta-Analysis of fMRI Studies

Prior research suggests that conscious face processing occurs preferentially in right hemisphere occipito-parietal regions. However, less is known about brain regions associated with non-conscious processing of faces, and whether a right-hemispheric dominance persists in line with specific affective responses. We aim to review the neural responses systematically, quantitatively, and qualitatively underlying subliminal face processing. PubMed was searched for Functional Magnetic Resonance Imaging (fMRI) publications assessing subliminal emotional face stimuli up to March 2022. Activation Likelihood Estimation (ALE) meta-analyses and narrative reviews were conducted on all studies that met ALE requirements. Risk of bias was assessed using the AXIS tool. In a meta-analysis of all 22 eligible studies (merging clinical and non-clinical populations, whole brain and region of interest analyses), bilateral amygdala activation was reported in the left (x = −19.2, y = 1.5, z = −17.1) in 59% of studies, and in the right (x = 24.4, y = −1.7, z = −17.4) in 68% of studies. In a second meta-analysis of non-clinical participants only (n = 18), bilateral amygdala was again reported in the left (x = −18, y = 3.9, z = −18.4) and right (x = 22.8, y = −0.9, z = −17.4) in 56% of studies for both clusters. In a final meta-analysis of whole-brain studies only (n=14), bilateral amygdala was also reported in the left (x = −20.2, y = 2.9, z = −17.2) in 64% of studies, and right (x = 24.2, y = −0.7, z = −17.8) in 71% of studies. The findings suggest that non-consciously detected emotional faces may influence amygdala activation, especially right-lateralized (a higher percentage of convergence in studies), which are integral for pre-conscious affect and long-term memory processing.

Neural activities during the Processing of unattended and unseen emotional faces: a voxel-wise Meta-analysis

Voxel-wise meta-analyses of task-evoked regional activity were conducted for healthy individuals during the unconscious processing of emotional and neutral faces with an aim to examine whether and how different experimental paradigms influenced brain activation patterns. Studies were categorized into sensory and attentional unawareness paradigms. Thirty-four fMRI studies including 883 healthy participants were identified. Across experimental paradigms, unaware emotional faces elicited stronger activation of the limbic system, striatum, inferior frontal gyrus, insula and the temporal lobe, compared to unaware neutral faces. Crucially, in attentional unawareness paradigms, unattended emotional faces elicited a right-lateralized increased activation (i.e., right amygdala, right temporal pole), suggesting a right hemisphere dominance for processing emotional faces during inattention. By contrast, in sensory unawareness paradigms, unseen emotional faces elicited increased activation of the left striatum, the left amygdala and the right middle temporal gyrus. Additionally, across paradigms, unconsciously processed positive emotions were found associated with more activation in temporal and parietal cortices whereas unconsciously processed negative emotions elicited stronger activation in subcortical regions, compared to neutral faces.