Cerebral lateralization of vigilance: A function of task difficulty

Functional near infrared spectroscopy (fNIRS) measures of cerebral oxygenation levels were collected from participants performing difficult and easy versions of a 12 min vigilance task and for controls who merely watched the displays without a work imperative. For the active participants, the fNIRS measurements in both vigilance tasks showed higher levels of cerebral activity than was present in the case of the no-work controls. In the easier task, greater activation was found in the right than in the left cerebral hemisphere, matching previous results indicating right hemisphere dominance for vigilance. However, for the more difficult task, this laterality difference was not found, instead activation was bilateral. Unilateral hemispheric activation in vigilance may be a result of employing relatively easy/simple tasks, not vigilance per se.     

Social competence with an unfamiliar peer in children and adolescents with high functioning autism: Measurement and individual differences

Children and adolescents with high functioning autism (HFA) display heterogeneity in social competence, which may be particularly evident during interactions with unfamiliar peers. The goal of this study was to examine predictors of social competence variability during an unfamiliar peer interaction. Thirty-nine participants with HFA and 39 age-, gender- and IQ-matched comparison participants were observed during dyadic laboratory interactions and detailed behavioral coding revealed three social competence dimensions: social initiative, social reciprocity, and social self-monitoring. Participants with HFA displayed higher social initiative but lower reciprocity than comparison participants. For participants with HFA, theory of mind was positively associated with observed initiative. For COM participants, social anxiety was negatively associated with reciprocity. However, for HFA participants, there was a quadratic relation between parent-reported social anxiety and observed reciprocity, demonstrating that low and high levels of anxiety were associated with low reciprocity. Results demonstrated the utility of our behavioral coding scheme as a valid assessment of social competence for children and adolescents with and without HFA. The curvilinear association between social anxiety and reciprocity highlights the importance of examining nonlinear relations in individuals with HFA, and emphasizes that discrete profiles of social anxiety in individuals with HFA may necessitate different treatment options.     

Cortical activation during executed, imagined, and observed foot movements

Evidence suggests that executed, imagined, and observed movements share neural substrates, however, brain activation during the performance of these three tasks has not yet been examined during lower extremity movements. Functional MRI was performed in 10 healthy right-footed participants during imagined, executed, and observed right ankle movements. Task compliance was high, confirmed via behavioral assessment and electromyographic measurements. Each task was also associated with its own profile of regional activation, however, overall, regional activation showed substantial overlap across the three lower extremity motor tasks. The findings suggest the utility of continued efforts to develop motor imagery and observation programs for improving lower extremity function in a range of clinical settings.     

Use of functional MRI in epilepsy]

For the purpose of examining pathophysiological mechanisms of a memory function in epileptic patients or an utility of fMRI for a presurgical assessment in neurosurgical treatment of epilepsy, activated areas in fMRI during verbal or visual memory task were investigated in patient group of temporal lobe epilepsy and normal subject group. Patient group of temporal lobe epilepsy consisted of 7 cases, of which 3 and 3 cases had left and right temporal foci, respectively, except 1 case having undetermined laterality of temporal foci. Normal subjects were 16 cases. All the epileptic and normal subjects were right-handed except for 1 lefty normal subject. Verbal memory tasks were composed of covert and overt recall tasks of 10 words given auditorily, while visual ones were recall tasks of 6 figures given visually. Eventually, in normal subjects, the left side-dominant medial frontal lobes including the superior frontal and anterior cingulate gyri were mainly activated in fMRI during the covert recall tasks of verbal memory, while the left side-dominant inferior frontal and precentral gyri as the motor language areas were chiefly activated in addition to the medial frontal lobe during the overt recall tasks. Further, the bilateral occipital lobes were activated in fMRI during the recall tasks of visual memory. Also in patient groups of temporal lobe epilepsy, the activated areas in fMRI during these tasks were the same as in normal subject group, regardless of the laterality of epileptic temporal foci. These results suggest that fMRI is useful for the determination of the lateralization of the cerebral hemisphere contributing to verbal memory function and therefore for the presurgical assessment of memory function in neurosurgical treatment of epilepsy.     

Lateralisation for processing facial emotion and anxiety: contrasting state, trait and social anxiety

Recent neuropsychological studies have attempted to distinguish between different types of anxiety by contrasting patterns of brain organisation or activation; however, lateralisation for processing emotional stimuli has received relatively little attention. This study examines the relationship between strength of lateralisation for the processing of facial expressions of emotion and three measures of anxiety: state anxiety, trait anxiety and social anxiety. Across all six of the basic emotions (anger, disgust, fear, happiness, sadness, surprise) the same patterns of association were found. Participants with high levels of trait anxiety were more strongly lateralised to the right hemisphere for processing facial emotion. In contrast, participants with high levels of self-reported physiological arousal in response to social anxiety were more weakly lateralised to the right hemisphere, or even lateralised to the left hemisphere, for the processing of facial emotion. There were also sex differences in these associations: the relationships were evident for males only. The finding of distinct patterns of lateralisation for trait anxiety and self-reported physiological arousal suggests different neural circuitry for trait and social anxiety.     

Neural response to monetary and social feedback demonstrates differential associations with depression and social anxiety

An aberrant neural response to rewards has been linked to both depression and social anxiety. Most studies have focused on the neural response to monetary rewards, and few have tested different modalities of reward (e.g. social) that are more salient to particular forms of psychopathology. In addition, most studies contain critical confounds, including contrasting positive and negative feedback and failing to disentangle being correct from obtaining positive feedback. In the present study, 204 participants underwent electroencephalography during monetary and social feedback tasks that were matched in trial structure, timing and feedback stimuli. The reward positivity (RewP) was measured in response to correctly identifying stimuli that resulted in monetary win, monetary loss, social like or social dislike feedback. All monetary and social tasks elicited a RewP, which were positively correlated. Across all tasks, the RewP was negatively associated with depression and positively associated with social anxiety. The RewP to social dislike feedback, independent of monetary and social like feedback, was also associated with social anxiety. The present study suggests that a domain-general neural response to correct feedback demonstrates a differential association with depression and social anxiety, but a domain-specific neural response to social dislike feedback is uniquely associated with social anxiety.     

Differential effects of left and right cerebral vascular accidents on language competency.

While language facility was once considered to be the sole province of the "dominant" left hemisphere, clinical and experimental findings suggest the right hemisphere plays an equally important role in many language tasks. To elucidate differential hemispheric language processes, Right Hemisphere Language Battery and Western Aphasia Battery data from left (LHD) and right (RHD) hemisphere cerebral vascular accident (CVA) patients and controls were subjected to multivariate discriminant analysis. The highly significant group differences and overall 95% classification rate obtained confirms the utility of the dependent measures in differential diagnosis. Results suggest CVA patients experience disparate language deficits, with the LHD group experiencing concordant-convergent language deficits and the RHD group displaying discordant-divergent deficits that interfere with the receptive and expressive language skills necessary for successful social discourse.     

Symmetry detection in typically and atypically speech lateralized individuals: A visual half-field study

Visuospatial functions are typically lateralized to the right cerebral hemisphere, giving rise to a left visual field advantage in visual half-field tasks. In a first study we investigated whether this is also true for symmetry detection off fixation. Twenty right-handed participants with left hemisphere speech dominance took part in a visual half-field experiment requiring them to judge the symmetry of 2-dimensional figures made by joining rectangles in symmetrical or asymmetrical ways. As expected, a significant left visual field advantage was observed for the symmetrical figures. In a second study, we replicated the study with 37 left-handed participants and left hemisphere speech dominance. We again found a left visual field advantage. Finally, in a third study, we included 17 participants with known right hemisphere dominance for speech (speech dominance had been identified with fMRI in an earlier study; Van der Haegen, Cai, Seurinck, & Brysbaert, 2011). Around half of these individuals showed a reversed pattern, i.e. a right visual half-field advantage for symmetric figures while the other half replicated the left visual-field advantage. These findings suggest that symmetry detection is indeed a cognitive function lateralized to the right hemisphere for the majority of the population. The data of the participants with atypical speech dominance are more in line with the idea that language and visuospatial functions are lateralized in opposite brain hemispheres than with the idea that different functions lateralize independently, although there seems to be more variability in this group.     

Cluster B personality symptoms in persons at genetic risk for schizophrenia are associated with social competence and activation of the right temporo-parietal junction during emotion processing

Personality disorders are common in nonpsychotic siblings of patients with schizophrenia, and some personality traits in this group may be associated with an increased risk for full-blown psychosis. We sought to establish if faulty right-hemisphere activation induced by social cognitive tasks, as previously described in patients with schizophrenia, is associated with specific personality symptoms in their unaffected siblings. We observed that cluster B personality symptoms in this group were inversely related to activation in the right temporo parietal junction (rTPJ, a structure critical in social cognitive processing) in response to a basic emotion processing task and also to social competence, whereas in contrast to our initial hypothesis, cluster A traits were not associated with right hemisphere activation during emotion processing or with social competence. These findings suggest the existence of clinical traits in at-risk individuals which share a common neurobiological substrate with schizophrenia, in regards to social performance.     

HEART RATE AND FLUENCY PERFORMANCE AMONG HIGH- AND LOW-ANXIOUS MEN FOLLOWING AUTONOMIC STRESS

Given the well-known associations between the right frontal lobe and negative effective states, as well as the involvement of the right posterior region in the modulation of autonomic nervous system arousal, anxiety is thought to be associated with relative right hemisphere activity (or decreased left hemisphere activity). However, recent evidence suggests that the left hemisphere predominantly modulates parasympathetic efferents, while the right hemisphere predominantly modulates sympathetic efferents of the autonomic nervous system. Thus, the left hemisphere should also play a role in anxiety, as anxiety is associated with decreased parasympathetic activity (increased heart rate). In order to investigate this hypothesis, the present experiment examined the influence of a well-known autonomic stressor (cold pressor) on heart rate (HR), and verbal and nonverbal fluency performance. Fifteen high level (HI) anxious and 15 low level (LO) anxious men completed verbal and nonverbal fluency measures after they were asked to place their left hand in ice water for 45 s. HI anxious subjects demonstrated opposing HR patterns during performance of the verbal (increased HR) and nonverbal (decreased HR) fluency tasks following cold pressor stimulation. In addition, HI anxious men generated fewer words per minute on the verbal fluency task than did LO anxious men. Although the data are supportive of functional right hemisphere activ ity among anxious individuals, the contribution of decreased left hemisphere activity (i.e., reduced parasympathetic activity and diminished verbal fluency performance) is also discussed.     

Measurement of brain activation during an upright stepping reaction task using functional near‐infrared spectroscopy

Functional near‐infrared spectroscopy (fNIRS) is a non‐invasive brain imaging technology that uses light to measure changes in cortical hemoglobin concentrations. FNIRS measurements are recorded through fiber optic cables, which allow the participant to wear the fNIRS sensors while standing upright. Thus, fNIRS technology is well suited to study cortical brain activity during upright balance, stepping, and gait tasks. In this study, fNIRS was used to measure changes in brain activation from the frontal, motor, and premotor brain regions during an upright step task that required subjects to step laterally in response to visual cues that required executive function control. We hypothesized that cognitive processing during complex stepping cues would elicit brain activation of the frontal cortex in areas involved in cognition. Our results show increased prefrontal activation associated with the processing of the stepping cues. Moreover, these results demonstrate the potential to use fNIRS to investigate cognitive processing during cognitively demanding balance and gait studies. Hum Brain Mapp 34:2817–2828, 2013. © 2012 Wiley Periodicals, Inc.     

Heart rate and fluency performance among high- and low-anxious men following autonomic stress

Given the well-known associations between the right frontal lobe and negative effective states, as well as the involvement of the right posterior region in the modulation of autonomic nervous system arousal, anxiety is thought to be associated with relative right hemisphere activity (or decreased left hemisphere activity). However, recent evidence suggests that the left hemisphere predominantly modulates parasympathetic efferents, while the right hemisphere predominantly modulates sympathetic efferents of the autonomic nervous system. Thus, the left hemisphere should also play a role in anxiety, as anxiety is associated with decreased parasympathetic activity (increased heart rate). In order to investigate this hypothesis, the present experiment examined the influence of a well-known autonomic stressor (cold pressor) on heart rate (HR), and verbal and nonverbal fluency performance. Fifteen high level (HI) anxious and 15 low level (LO) anxious men completed verbal and nonverbal fluency measures after they were asked to place their left hand in ice water for 45 s. HI anxious subjects demonstrated opposing HR patterns during performance of the verbal (increased HR) and nonverbal (decreased HR) fluency tasks following cold pressor stimulation. In addition, HI anxious men generated fewer words per minute on the verbal fluency task than did LO anxious men. Although the data are supportive of functional right hemisphere activity among anxious individuals, the contribution of decreased left hemisphere activity (i.e., reduced parasympathetic activity and diminished verbal fluency performance) is also discussed.     

The effect of acute ethanol challenge on global visuospatial attention: Exaggeration of leftward bias in line bisection

Acute alcohol challenge has been associated with a selective impairment of right hemisphere function. A hallmark of visuospatial neglect syndrome is that patients with right hemisphere lesions misbisect horizontal lines far rightward of veridical centre. Neurologically intact participants misbisect lines with a systematic leftward bias (pseudoneglect). Neuroimaging studies in neurologically intact participants reveal predominant right hemisphere activation during performance of line bisection tasks. The current study assessed whether acute alcohol challenge alters global visuospatial attention. Participants (N=18; 10 male; strongly right-handed; mean age 23 years) engaged in a forced-choice tachistoscopic line bisection task in both ethanol challenge (mean BAC=.077) and no ethanol control conditions. Mean leftward bisection error in the control condition was ?0.238 degrees visual angle (1.05% line length), and leftward bisection error significantly increased (p=.001) under ethanol challenge (?0.333 degrees visual angle, 1.47% line length). Mean bisection precision in the control condition was 0.358 degrees visual angle (1.58% line length); bisection precision significantly deteriorated (p=.008) under ethanol challenge (0.489 degrees, 2.17% line length). Decreased bisection precision indicates that ethanol disrupts the fidelity of visuospatial performance. The exaggerated leftward bisection error implies that ethanol may exert a differential effect on left versus right hemispheric function with respect to the control of global visuospatial attention.     

Cortical hemodynamic mechanisms of reversal learning using high-resolution functional near-infrared spectroscopy: A pilot study

ObjectivesReversal learning is widely used to analyze cognitive flexibility and characterize behavioral abnormalities associated with impulsivity and disinhibition. Recent studies using fMRI have focused on regions involved in reversal learning with negative and positive reinforcers. Although the frontal cortex has been consistently implicated in reversal learning, few studies have focused on whether reward and punishment may have different effects on lateral frontal structures in these tasks.MethodsDuring this pilot study on eight healthy subjects, we used functional near infra-red spectroscopy (fNIRS) to characterize brain activity dynamics and differentiate the involvement of frontal structures in learning driven by reward and punishment.ResultsWe observed functional hemispheric asymmetries between punishment and reward processing by fNIRS following reversal of a learned rule. Moreover, the left dorsolateral prefrontal cortex (l-DLPFC) and inferior frontal gyrus (IFG) were activated under the reward condition only, whereas the orbito-frontal cortex (OFC) was significantly activated under the punishment condition, with a tendency towards activation for the right cortical hemisphere (r-DLPFC and r-IFG). Our results are compatible with the suggestion that the DLPFC is involved in the detection of contingency change. We propose a new representation for reward and punishment, with left lateralization for the reward process.ConclusionsThe results of this pilot study provide insights into the indirect neural mechanisms of reversal learning and behavioral flexibility and confirm the use of fNIRS imaging in reversal-learning tasks as a translational strategy, particularly in subjects who cannot undergo fMRI recordings.     

Assessed and distressed: white-coat effects on clinical balance performance

Objectives

While balance in young and older adults is known to change with the threat of standing on elevated surfaces, the potential for social anxiety to influence emotional states and balance performance during a clinical assessment is currently unknown.

Methods

Nineteen young and 19 older healthy female adults volunteered for the study. The effects of age and clinical assessment on balance performance were examined using a 2×2 between- and within-subjects factorial design. Balance performance measures were derived from forceplate recordings of three different postural tasks. Psychological measures included fear of negative evaluation, state anxiety, and fear related to the completed balance tasks.

Results

There was a significant increase in state anxiety and fear when participants performed balance tasks while being assessed by an evaluator. Compared to the control condition, both age groups leaned significantly further forward during the functional reach task when being assessed. While being assessed, older adults had significantly larger amplitudes and frequencies of center of pressure (COP) displacement during two-legged stance with eyes closed (EC) and significantly less stance time during one-legged standing compared to the control condition. In contrast, balance performance in young adults during one-legged or two-legged stance tasks was unchanged by clinical assessment.

Conclusions

Social anxiety associated with the clinical assessment of balance can have a negative influence on both emotional states and balance control. As a result, clinicians need to recognize and account or control for potential social anxiety effects on clinical balance performance in young and older adults in particular.     

How cognitive performance‐induced stress can influence right VLPFC activation: An fMRI study in healthy subjects and in patients with social phobia

The neural bases of interactions between anxiety and cognitive control are not fully understood. We conducted an fMRI study in healthy participants and in patients with an anxiety disorder (social phobia) to determine the impact of stress on the brain network involved in cognitive control. Participants performed two working memory tasks that differed in their level of performance‐induced stress. In both groups, the cognitive tasks activated a frontoparietal network, involved in working memory tasks. A supplementary activation was observed in the right ventrolateral prefrontal cortex (VLPFC) in patients during the more stressful cognitive task. Region of interest analyses showed that activation in the right VLPFC decreased in the more stressful condition as compared to the less stressful one in healthy subjects and remain at a similar level in the two cognitive tasks in patients. This pattern was specific to the right when compared to the left VLPFC activation. Anxiety was positively correlated with right VLPFC activation across groups. Finally, left dorsolateral prefrontal cortex (DLPFC) activation was higher in healthy subjects than in patients in the more stressful task. These findings demonstrate that in healthy subjects, stress induces an increased activation in left DLPFC, a critical region for cognitive control, and a decreased activation in the right VLPFC, an area associated with anxiety. In patients, the differential modulation between these dorsal and ventral PFC regions disappears. This absence of modulation may limit anxious patients' ability to adapt to demanding cognitive control tasks. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc     

The relationship between dorsolateral prefrontal activation and speech performance-based social anxiety using functional near infrared spectroscopy

Functional near-infrared (fNIR) spectroscopy is a promising new technology that has demonstrated utility in the study of normal human cognition. We utilized fNIR spectroscopy to examine the effect of social anxiety and performance on hemodynamic activity in the dorsolateral prefrontal cortex (DLPFC). Socially phobic participants and non-clinical participants with varying levels of social anxiety completed a public speaking task in front of a small virtual audience while the DLPFC was being monitored by the fNIR device. The relationship between anxiety and both blood volume (BV) and deoxygenated hemoglobin (Hb) varied significantly as a function of speech performance, such that individuals with low social anxiety who performed well showed an increase in DLPFC activation relative to those who did not perform well. This result suggests that effortful thinking and/or efficient top-down inhibitory control may have been required to complete an impromptu speech task with good performance. In contrast, good performers who were highly socially anxious showed lower DLPFC activation relative to good performers who were low in social anxiety, suggesting autopilot thinking or less-effortful thinking. In poor performers, slight increases in DLPFC activation were observed from low to highly anxious individuals, which may reflect a shift from effortless thinking to heightened self-focused attention. Heightened self-focused attention, poor inhibitory control resulting in excessive fear or anxiety, or low motivation may lower performance. These results suggest that there can be different underlying mechanisms in the brain that affect the level of speech performance in individuals with varying degrees of social anxiety. This study highlights the utility of the fNIR device in the assessment of changes in DLPFC in response to exposure to realistic phobic stimuli, and further supports the potential utility of this technology in the study of the neurophysiology of anxiety disorders.     

Does hemispheric lateralization influence therapeutic effects of transcranial direct current stimulation?

This study investigated the effect of transcranial direct current stimulation(t DCS) polarity depending on lateralized function of task property in normal individuals performing visuomotor and simple repetitive tasks. Thirty healthy participants with no neurological disorders were recruited to participate in this study. Participants were randomly allocated into active or control condition. For the active condition, t DCS intensity was 2 m A with stimulation applied for 15 minutes to the right hemisphere(t DCS condition). For the sham control, electrodes were placed in the same position, but the stimulator was turned off after 30 seconds(sham condition). The tapping and tracking task tests were performed before and after for both conditions. Univariate analysis revealed significant difference only in the tracking task. For direct comparison of both tasks within each group, the tracking task had significantly higher Z score than the tapping task in the t DCS group(P 0.05). Thus, our study indicates that stimulation of the right hemisphere using t DCS can effectively improve visuomotor(tracking) task over simple repetitive(tapping) task.     

Right–left discrimination is related to the right hemisphere

We aimed to determine the functional localisation of right–left discrimination (RLD) by functional MRI (fMRI). In this study, 16 male volunteers were examined. There were three task sessions: one active and two baseline tasks. During the baseline tasks participants were instructed to show numbers with their fingers. The first baseline task was performed with the right hand, the second one with the left hand. During the active (RLD) task participants were also instructed to show numbers. The difference between baseline and active tasks was that during the active task the hand with which the participant should perform the instruction was assigned randomly. Thus, participants were unaware which hand should be used before the instruction command. During RLD, activations occurred in the right-sided frontal, precuneus, postcentral, angular, lingual, and superior temporal gyri. Activations also appeared in the left-sided temporal gyri and precuneus. Of the activations, 76.7% appeared in the right hemisphere, 23.3% in the left hemisphere. Conclusively, we found that RLD is mainly related to the right hemisphere, and requires activation of the parieto-temporo-occipital junction and the visual system including cuneus, precuneus, and gyrus lingualis.     

Linear association between social anxiety symptoms and neural activations to angry faces: from subclinical to clinical levels

Social anxiety disorder (SAD), which is characterized by the fear of being rejected and negatively evaluated, involves altered brain activation during the processing of negative emotions in a social context. Although associated temperament traits, such as shyness or behavioral inhibition, have been studied, there is still insufficient knowledge to support the dimensional approach, which assumes a continuum from subclinical to clinical levels of social anxiety symptoms. This study used functional magnetic resonance imaging (fMRI) to examine the neural bases of individual differences in social anxiety. Our sample included participants with both healthy/subclinical as well as clinical levels of social anxiety. Forty-six participants with a wide range of social anxiety levels performed a gender decision task with emotional facial expressions during fMRI scanning. Activation in the left anterior insula and right lateral prefrontal cortex in response to angry faces was positively correlated with the level of social anxiety in a regression analysis. The results substantiate, with a dimensional approach, those obtained in previous studies that involved SAD patients or healthy and subclinical participants. It may help to refine further therapeutic strategies based on markers of social anxiety.