Social exclusion refers to the experience of rejection by one or more people during a social event and can induce pain-related sensations. Cyberball, a computer program, is one of the most common tools for analyzing social exclusion. Regions of the brain that underlie social pain include networks linked to the dorsal lateral prefrontal cortex (DLPFC). Specifically, self-directed negative socially induced exclusion is associated with changes in DLPFC activity. Direct manipulation of this area may provide a better understanding of how the DLPFC can influence the perception of social exclusion and determine a causal role of the DLPFC. Transcranial magnetic stimulation (TMS) was applied to both the left and right DLPFC to gauge different reactions to the Cyberball experience. It was found that there were elevated exclusion indices following right DLPFC rTMS; participants consistently felt more excluded when the right DLPFC was excited. This may relate to greater feelings of social pain when the right DLPFC is manipulated. These data demonstrate that direct manipulation of the DLPFC results in changes in responses to social exclusion.

"Manipulations differentially activating the left or right cerebral hemisphere influence behavior in ways congruent with known theories of hemispheric lateralization of function. For example, rightward eye gaze increases positive mood via left hemisphere activity, and left unilateral nostril breathing increases right hemisphere spatial task performance. Determining under what conditions, and to what extent, simple techniques can be used to alter mental and emotional state holds considerable appeal because methods might be used as adjuncts to other tactics to mitigate negative affect in clinical situations, or to improve cognition in neurocognitive impairment. One method demonstrating promise for altering cognition and emotion, and that could be used in home-settings, is sustained unilateral hand clenching. The goal of the present paper was to analyze the literature to examine i. typical methods used for this manipulation; ii. in what manner such movements alter cognition and/or emotion; iii. whether one versus the other hemisphere, is particularly affected by manipulation. A literature search was conducted using relevant search terms, resulting in 24 articles. Across the literature, a wide range of domains was examined, including memory, decision making, creativity, language, emotion, and social perception, with many examining more than one domain. Nine included neurophysiological measures. Overall, 4 studies reported an impact of only unilateral right-hand clenching and 5 of only unilateral left-hand clenching, on behavior. Twelve reported an impact of both hand clenching conditions. Three reported no impact of hand clenching on performance. Future work should examine unilateral hand clenching in clinical populations."

Objective Prior work raises the interesting possibility that both multiple sclerosis and synesthesia share a common etiology, that being immune system dysfunction, as well as neuroanatomical and neurochemical abnormalities, including those involving white matter and serotonergic pathways, respectively. Given these links between these two syndromes, we examined the possibility that prevalence of synesthesia would be elevated in a population of individuals with MS, relative to what is thought to be the prevalence in the neurotypical population. It was not known whether synesthesia might be a marker for subsequent development of MS, or if synesthesia might reflect neurological damage resulting from MS disease progression. Method Individuals with selfreported clinically definite MS were recruited online via the internet and social media using sites specifically relevant to the MS community. Data from 147 individuals who completed several questionnaires related to synesthesia were analyzed. Results Depending on criteria, between approximately 7 and 16% of individuals with MS reported synesthesia here. This is an estimated 1.57 to 3.55 times increased incidence of synesthesia here relative to previous findings in neurotypical samples. Limitations of the study include that this was an internet survey, and that synesthesia was not directly assessed in this sample. Conclusions Results suggest a link between the syndromes, primarily indicating that synesthesia may be a marker for subsequent MS development, and the implications and directions for future study are discussed.

Coronavirus-2019 (COVID-19), the disease caused by Severe Acute Respiratory Syndrome 2019 (SARS-CoV-19) results in heterogenous symptoms, with outcomes ranging from asymptomatic to death. (1)Markers predicting disease severity, and suggesting methods of treatment, are critically needed.Symptoms of anosmia/ageusia reported in COVID-19 may reflect an adaptive response of locally decreased nasopharyngeal zinc (Zn), ultimately resulting in decreased ACE-2, (2) a crucial receptor for Sars-CoV-19 binding.Such locally decreased Zn response was suggested to result in subsequently decreased COVID-19 severity. (2)issing from discussion of COVID-19-induced anosmia/ ageusia is reference to older literature demonstrating associations between viral infection and altered taste/smell, and between these variables and Zn deficiency.In a sample of 35 individuals reporting taste/smell dysfunction, 51% reported it occurred immediately prior to/concurrent with, respiratory illness.Zn mitigated symptoms, though administration protocol was not described. (3)In a group of 103 people with altered taste/smell, 57% reported abrupt onset "during or soon after a respiratory illness", with three-days or more of fever also demonstrating association.Zn levels were decreased in those with taste/smell disruption, and Zn (zinc sulfate) supplementation mitigated the symptoms in a single-blind study. (4)f mechanisms involved in smell/taste alteration in/following other illnesses is similar to that which occurs during COVID-19,

Location information is processed through two types of spatial processing; categorical and coordinate processing. Categorical spatial relations indicate where an object is relative to another object, without regard to the metric distance between the two objects. Coordinate spatial relations indicate metric distance without regard to relative location. In human behavioral studies, the magnocellular pathway of the lateral geniculate nucleus has been implicated in coordinate spatial processing abilities. Magnocellular pathway cells (type IV) have a center surround organization, such that red light inhibits neuronal firing. In these behavioral studies, red stimuli decreases coordinate spatial processing accuracy. Prior studies also show that there is a lag between the time of visual stimulus presentation and the time of observing a neural response in the magnocellular pathway. We sought to understand whether prior presentation of red stimuli decreases coordinate spatial performance, and also examined its effects on categorical spatial performance. The results indicate that prior presentation of red stimuli decreases accuracy and perceived confidence on both the categorical and coordinate tasks. These results confirm prior findings of the association between magnocellular pathway function and coordinate spatial processing. Implications for categorical task results and associated neural pathways are discussed.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic, in part due to the highly infectious nature of the disease. Because SARS-CoV-2 is new, much is unknown regarding mechanisms of transmission, and such information is urgently needed. Here, based on previous findings from related human betacoronaviruses, it is suggested that one possible route of transmission may be via infectious sweat. It is suggested that research be conducted in order to determine whether sweat in SARS-CoV-2 infected individuals harbors virus in quantities that can infect others. Findings could be used for formulations of mitigation strategies and empirically based public health messaging.

Individual differences in handedness in episodic memory have been demonstrated across a wide variety of stimuli and protocols. with inconsistent-handers (ICH) having superior memory relative to consistent-right-handers (CRH). The current study looks at the question of whether ICH also report better subjective memory. Prior work shows that objective and subjective memory performance are generally unrelated, but the current study found that ICH indeed report better subjective memory, as measured by the Cognitive Failures Questionnaire. Given evidence for associations between personality factors and subjective memory, the current study also looked at the Behavioral Inhibition Scale (BIS) and found (i) no handedness differences on the BIS, but (ii) a negative association between neuroticism and cognitive failures in CRH.

A previous study reported superior categorical and coordinate spatial task performance in inconsistent-versus consistent-right-handers (ICH versus CRH). Propper et al. used a three-dimensional (3D) computer-based task wherein individuals navigated to 21 locations within a realistic cityscape. During testing, participants were queried on their categorical and coordinate spatial knowledge of the map. In that study, the categorical and coordinate tasks may have inadvertently encouraged language coding of learned spatial information, potentially confounding spatial processing with recall ability for language-based information. Also, that study used a between-subjects design, which precludes examination of relationships between spatial knowledge as a function of handedness. The present study duplicated the learning task in Propper et al. using test stimuli that more faithfully represent spatial, and not language-based, information, as well as a within-subjects design. Results did not significantly replicate the previous study. Possible reasons for this finding are discussed.

Categorical versus coordinate spatial tasks rely differentially on the left versus right hemisphere. Given the neuroanatomical and neurophysiological differences between inconsistent- versus consistent-right-handers (ICH versus CRH, respectively), such that the former demonstrates increased access to right hemisphere processes relative to the latter, it was hypothesized that ICH would outperform CRH on a test of coordinate spatial knowledge. Previous work demonstrating reliance on the right hemisphere for both categorical and coordinate information in non-right-handers using lateralized stimuli of brief duration suggested ICH might also outperform CRH on a categorical task as well. Participants navigated a virtual environment, landmark-to-landmark, within a 3-dimensional first-person point of view with high ecological validity, and then were tested on either their categorical or coordinate spatial knowledge. ICH were superior relative to the CRH on both types of spatial knowledge. Additionally, ICH navigated the environment during learning more quickly, and reported being more confident in their knowledge of the location of landmarks within the environment, compared with CRH. Results are discussed in terms of potential handedness differences in spatial ability generally.

Discrepant input from vestibular and visual systems may be involved in motion sickness; individual differences in the organization of these systems may therefore give rise to individual differences in propensity to motion sickness. Non-right-handedness has been associated with altered cortical lateralization of vestibular function, such that non-right-handedness is associated with left hemisphere, and right-handedness with right hemisphere, lateralized, vestibular system. Interestingly, magnocellular visual processing, responsible for motion detection and ostensibly involved in motion sickness, has been shown to be decreased in non-right-handers. It is not known if the anomalous organization of the vestibular or magnocellular systems in non-right-handers might alter susceptibility to motion sickness. Undergraduate college students completed online versions of the Edinburgh Handedness Inventory (Oldfield, Neuropsychologia 9:97–113, 1971) and Motion Sickness Susceptibility Questionnaire – Short Form (Golding, Personality and Individual Differences 41:237–48, 2006). Data from 664 undergraduate men and women revealed no support for individual differences in handedness effects on self-reported propensity to experience motion sickness in either childhood or adulthood. Findings replicate previous work of increased motion sickness in women, compared with men. Men reported being less motion sick in adulthood compared to childhood, while women reported no differences in motion sickness between childhood and adulthood. Handedness results are discussed in the context of reported individual differences in handedness effects on memory, and gender effects in terms of social desirability. Given that the handedness groups demonstrate differences in brain organization, the null effects here may shed light on the neural mechanisms that are involved in motion sickness.

Sustained unilateral hand clenching alters perceptual processing and affective/motivational state, with these alterations presumed to reflect increased hemispheric activity contralateral to the side of motor movement. However, data from electroencephalographic and imaging studies are contradictory regarding the relationship between sustained hand clenching and brain activity. In order to investigate the relationship between brain activity, sustained unilateral hand clenching, and changes in affect and perceptual processing, frontal hemispheric activity was measured via functional near-infrared spectroscopy (fNIRS), using derived O(2)Hb prior to, during, and post-sustained unilateral hand clench. Participants' mood and spatial perception were recorded pre- and post-clenching. Sustained unilateral hand clenching altered brain activity and mood, but not spatial perception. Results revealed increased O(2)Hb bilaterally following sustained unilateral hand clenching, relative to baseline, regardless of hand. In agreement with previous fNIRS studies, sustained unilateral hand clenching resulted in greater ipsilateral, compared with contralateral, O(2)Hb. An interaction between side of hand clench and change in mood was in the direction predicted by theories of hemispheric lateralization of emotion: Following left-hand clenching, individuals became more affectively negative, and following right-hand clenching, they became more affectively positive.

A large body of evidence supports the existence of a robust handedness difference in episodic memory retrieval, with inconsistent-handedness being associated with superior memory across a wide variety of paradigms, including superior retrieval of lab-based and real world memories. Despite superior episidoc memory in inconsistent-handers, and despite neuroanatomical and neurophysiological differences in cortical regions between inconsistent- and consistent-handers, we are aware of no studies to date that have examined physiological activity in the brains of inconsistent- versus consistent-handers while engaged in memory tasks. The purpose of this paper, therefore, is to present a first look at this issue, using functional near-infrared spectroscopy (fNIRS) as a simple, non-invasive measure of frontal lobe activity during encoding and recall of list words in inconsistent- and consistent-handers. Behaviourally, we replicated prior studies, finding a significant inconsistent-handed advantage in free recall. Using fNIRS-derived oxygenated haemoglobin (O(2)Hb) as a measure of frontal lobe activity, we found the first evidence for handedness differences in brain activity that are associated with the handedness differences in episodic retrieval. Specifically, the primary finding was that increased O(2)Hb in the right hemisphere during recall was associated with better retrieval, but for consistent-handers only.

Past studies have independently shown associations of working memory and degree of handedness with episodic memory retrieval. The current study takes a step ahead by examining whether handedness and working memory independently predict episodic memory. In agreement with past studies, there was an inconsistent-handed advantage for episodic memory; however, this advantage was absent for working memory tasks. Furthermore, regression analyses showed handedness, and complex working memory predicted episodic memory performance at different times. Results are discussed in light of theories of episodic memory and hemispheric interaction.

The present research examined the effects of pre-encoding and pre-recall induced mood on episodic memory. It was hypothesized that happy and/or angry mood prior to encoding (increasing left hemisphere activity), in tandem with fearful mood prior to recall (increasing right hemisphere activity) would be associated with superior episodic memory. It was also hypothesized that tympanic membrane measures (TMT), indicative of hemispheric activity, would change as a function of induced mood. Although subjectively-experienced mood induction was successful, pre-encoding and pre-recall mood did not alter memory, and only altered TMT in the pre-encoding fear and pre-recall angry mood induction conditions. Interestingly, baseline absolute difference between left and right TMT, a measure of differential hemispheric activity, regardless of the direction of that activity, was significantly positively related to number of total words written, number of correctly recalled words, and corrected recall score. This same TMT measure pre-encoding, regardless of specific mood, was significantly negatively related to false recall. Results are discussed in terms the HERA model of episodic memory, and in the nature of interhemispheric interaction involved in episodic recall.

The goal of this Research Topic was to bring together diverse scientific perspectives on lateralized brain mechanisms underlying emotion, motivation, and memory. The Topic resulted in eight articles, three of which report original research and five of which review and synthesize past research with the aim of developing new hypotheses and theory. A range of international experts with diverse backgrounds, theoretical perspectives, and experimental methods contributed to the Topic. Contributions strongly reflect this diversity, ranging from examining pupil dilation in response to viewing Rembrandt portraits to understanding how caffeine supplementation influences levels of spatial processing. In all cases, the authors developed strong, empirically guided insights into the lateralized brain mechanisms underlying behavioral effects. Two primary themes emerge to guide and constrain continuing research. The first theme is related to dynamic interhemispheric interactions that subserve emotion, motivational states, and memory. Elizabeth Shobe’s article, Independent and Collaborative Contributions of the Cerebral Hemispheres to Emotional Processing (Shobe, 2014) proposes a framework for understanding the interaction of lateralized brain mechanisms for identifying and understanding emotional stimuli and engaging in higher-order emotional processing. Under this framework, the right hemisphere engages subcortical structures with the goal of identifying and comprehending positive and negative emotional stimuli, whereas the left hemisphere contributes to higher-level processing such as emotion regulation and adaptation. Critically, dynamic interhemispheric interactions provide the left hemisphere with the information it needs to execute relatively strategic processes. Spielberg and colleagues emphasize the importance of lateralized approach versus avoidance networks in guiding human behavior. In their article, Hierarchical Brain Networks Active in Approach and Avoidance Goal Pursuit (Spielberg et al., 2013), the authors propose a hierarchical model consisting of four levels: tactical, strategic, system, and temperamental, following a neurally inspired abstraction gradient along posterior to anterior areas of the prefrontal cortex. Right hemisphere regions process and update avoidance goals, and left hemisphere regions govern approach goals. The model dictates both intrahemispheric interactions across hierarchical layers, and also interhemispheric interactions that cut across both abstraction levels and motivational states; together, these interactions guide, constrain, and update goal-directed behavior over time. Two particular original research contributions also fit the theme related to interhemispheric interaction. The first is Parker and colleagues’ Effects of Saccadic Bilateral Eye Movements on Episodic and Semantic Autobiographical Memory Fluency (Parker et al., 2013), demonstrating that horizontal saccadic eye movements enhance episodic but not semantic autobiographical memory retrieval. In accounting for these results, the authors point to the hemispheric encoding/retrieval asymmetry (HERA; Habib et al., 2003) model and its suggestion that episodic memory retrieval depends on efficient and dynamic interhemispheric interactions. They also suggest that saccadic eye movements may induce transient increases in executive function that serve to direct attention toward recalling specific episodic details, which is a unique proposition that will likely motivate subsequent research expanding the nature and scope of dependent measures used in these types of experiments. The second original research contribution fitting the theme of interhemispheric interaction is provided by Edlin and colleagues in their article Memory for Hand-use Depends on Consistency of Handedness (Edlin et al., 2013), demonstrating that inconsistent handedness enhances episodic memory for manual actions. Inconsistent-handers more frequently engage bilateral motor regions of the brain, and also have larger corpora callosa relative to consistent-handers, suggesting that increased hemispheric interaction may underlie these reported effects. The second theme that emerged from this Research Topic is identifying and characterizing lateralized processes in both human beings and non-human primates. In this theme, very diverse contributions were made characterizing the universality of lateralized emotion perception and expression across primates on the one and hand, and artistically, nutritionally, and clinically altering levels of lateralized task engagement on the other. Lindell contributed a review article, Continuities in Emotion Lateralization in Human and Non-human Primates (Lindell, 2013), providing compelling evidence that both human beings and non-human primates, including rhesus macaques and chimpanzees, use primarily right hemisphere brain mechanisms for generating and perceiving facial emotions, suggesting some universality of lateralized emotional expression and perception. Two other reviews examined lateralized contributions to perception and memory. First, Willment and Golby (2013) support a material-specific model of how focal pathology and surgical management of temporal lobe epilepsy can result in predictable memory deficits, with left and right temporal regions mediating verbal and non-verbal memories, respectively. Such material-specific links can inform preoperative fMRI memory mapping aimed at predicting and managing post-operative memory outcomes. This is an exciting prospect, and demonstrates a promising avenue for transitioning research on lateralized emotion and memory to high stakes clinical settings. Second, Schirillo (2013) demonstrates that viewing male Rembrandt portraits reliably produced pupil dilations when the portraits were rated as low or high in valence. The author suggests that right lateralized brain mechanisms responsible for emotion perception may explain why some artists may choose to depict the right cheek of male figures, but the left cheek of female figures, perhaps promoting perceptions of dominance in male figures. The final contribution related to identifying and characterizing lateralized processes was provided by Giles and colleagues in their article Caffeine Promotes Global Spatial Processing in Habitual and Non-habitual Caffeine Consumers (Giles et al., 2013). The authors found that increasing doses of caffeine promoted memory for distal but not proximal landmark relationships during a spatial memory test. They suggest that such global enhancement may be related to caffeine-induced upregulation of brain dopamine, serotonin, and norepinephrine, neurotransmitter systems that may be higher density in right versus left hemisphere brain regions. The diverse articles published under this Research Topic advance theoretical positions related to interactive contributions of brain hemispheres toward a broad range of cognitive functions related to emotion and memory, and highlight important characteristics of lateralized mechanisms in human and non-human primates. Relatively, integrated perspectives on brain involvement across a range of cognitive tasks provide stimulating theoretical frameworks for reconciling a range of experimental findings and motivating future research. Specific outstanding questions raised by the Research Topic include: (1) How might other individual differences modulate lateralized and bilaterally interactive brain mechanisms involved in processing specialized information types and maintaining and updating motivational states and goals? (2) Contrasting accounts of hemispheric differences in affective and motivational processing were presented. How can we devise research paradigms to test the relative validity of these models? (3) Much of this work infers lateralized processes from behavior, but how might functional connectivity analyses advance our understanding, for instance by exploring interhemispheric communication as a result of saccadic eye movements or inconsistent handedness? (4) How might a wider range of nutritional influences, including psychostimulants and amino acids, bias attention, perception, and memory toward particular information types, motivational states, arousal, and mood states, or levels of focus? (5) How can better understanding lateralized and bilateral interactive brain processes inform applied interventions for clinical or performance-based domains, including predicting surgical outcomes, and informing targeted neuromodulation (i.e., TMS, tDCS)?

Unilateral hand clenching increases neuronal activity in the frontal lobe of the contralateral hemisphere. Such hand clenching is also associated with increased experiencing of a given hemisphere's "mode of processing." Together, these findings suggest that unilateral hand clenching can be used to test hypotheses concerning the specializations of the cerebral hemispheres during memory encoding and retrieval. We investigated this possibility by testing effects of unilateral hand clenching on episodic memory. The hemispheric Encoding/Retrieval Asymmetry (HERA) model proposes left prefrontal regions are associated with encoding, and right prefrontal regions with retrieval, of episodic memories. It was hypothesized that right hand clenching (left hemisphere activation) pre-encoding, and left hand clenching (right hemisphere activation) pre-recall, would result in superior memory. Results supported the HERA model. Also supported was that simple unilateral hand clenching can be used as a means by which the functional specializations of the cerebral hemispheres can be investigated in intact humans.

A growing body of evidence is reviewed showing that degree of handedness (consistent versus inconsistent) is a more powerful and appropriate way to classify handedness than the traditional one based on direction (right versus left). Experimental studies from the domains of episodic memory retrieval, belief updating/cognitive flexibility, risk perception, and more are described. These results suggest that inconsistent handedness is associated with increased interhemispheric interaction and increased access to processes localized to the right cerebral hemisphere.

Left-handers are reputed to be shorter than right-handers.However, previous research has confounded handedness direction (left-versus right-handedness) with handedness strength (consistency with which one hand is chosen across a variety of tasks; consistent-versus inconsistent-handedness).Here, we support a relationship between handedness strength, but not direction, and stature, with increasing inconsistent-handedness associated with increasing self-reported height.