The effect of tDCS electrode montage on attention and working memory.

The effects of transcranial direct current stimulation (tDCS) for improving attention and working memory have been generally mixed and small, potentially due to variability between studies with montages, stimulus parameters and outcome measures. The tDCS montage is an important parameter which determines the degree and intensity of stimulation in targeted brain regions. This study aimed to examine the effects of using three different montages for modulating attention and working memory performance: Bi-frontal, Broad-frontal and Broad-parietal. Ninety-three healthy adults participated in a counterbalanced cross-over study. Participants received both active and sham tDCS with either the Bi-frontal, Broad-frontal or Broad-parietal montage during performance of both a 1- and 2-back task. TDCS montage moderated 2-back working memory reaction time performance, though not accuracy, with faster reaction times observed for active compared to sham tDCS with the Broad-frontal montage only (F (1,90) = 5.26, p = .024, η2 = 0.06). TDCS montage did not significantly moderate performance on the 1-back task. The cognitive effects of tDCS varied according to montage, task, and outcome measure. TDCS administered with the cathode placed extracephalically in a Broad-frontal montage may be beneficial for improving working memory.

Stimulus intensity effects and sequential processing in the passive auditory ERP.

Auditory stimulus intensity of innocuous tones is generally thought to have a direct effect on the amplitude of ERP components, but these effects have rarely been explored across a wide component range, or in multiple paradigms. Here we investigate component sensitivity to stimulus intensity differences in two studies. Study 1 (N = 36) employed a between-participants paradigm in which repeated trains of standard stimuli were presented as 50 or 80 dB SPL 1000 Hz tones. Study 2 (N = 18) used a within-participant presentation of alternating 60 and 80 dB SPL 1000 Hz tones. Electrode caps with 19 channels (referred to linked ears) generated ERPs covering the first 600 ms of each participant's EEG responses; these were submitted to separate temporal PCAs in each study. A similar series of components was obtained in each study: P1, N1a, N1b, N1c, P2, P3a, P3b, nP3, SW1, and SW2; an N2 was found in Study 2 only. Loud tones in Study 1 produced greater amplitudes in all components except SW1. In Study 2, Loud cf. Soft tones produced smaller P1 and nP3, larger N1 components, P2, and P3a, with no effect on N2, P3b, SW1 or SW2. These results indicate similar sequential processes underlying sensory processing in one- and two-stimulus paradigms, with the later stimulus intensity effects varying with paradigm.

tDCS effects on task-related activation and working memory performance in traumatic brain injury: A within group randomized controlled trial.

Non-invasive transcranial direct current stimulation (tDCS) has been reported to facilitate working memory in normal adults. There is some evidence in people with Traumatic Brain Injury (TBI) but overall evidence is mixed. This study aimed to address shortcomings of prior study designs in TBI to examine whether a single dose of tDCS would lead to benefits in working memory. Thirty people with severe, chronic TBI were administered a single session of either anodal tDCS (2 mA for 20 min) or sham tDCS (2 mA for 30 s), in a counterbalanced order, over the left parietal cortex while performing 1-back and 2-back working memory tasks. Skin conductance levels were examined as a measure of task activated arousal, a possible functional analogue of cortical excitability. We found that tDCS led to no improvements in accuracy on the working memory tasks. A slight increase in variability and reaction time with tDCS was related to decreased task activated arousal. Overall, this study yielded no evidence that a single session of tDCS can facilitate working memory for people with TBI.

Empathy for people with similar experiences: Can the perception-action model explain empathy impairments after traumatic brain injury?

Introduction: A significant proportion of people with traumatic brain injury (TBI) report low levels of empathy, yet there is a paucity of research investigating the mechanisms which underpin this. In this study, we investigated empathy after TBI through the lens of the perception-action model of empathy. Specifically, we looked at the effect of similarity of experience on self-reported empathy and skin conductance in participants with TBI and controls.Method: Thirty people with a traumatic brain injury and 30 matched healthy controls initially recounted three emotional events they had experienced in the past (one happy, one angry and one sad). Then, at a second visit, participants heard three stories which were written to be similar their own stories and three which were based on someone else's stories. We recorded skin conductance while participants listened and then collected self-reported levels of empathy for protagonists in the stories.Results: We found that self-reported empathy, but not skin conductance levels, was greater for similar compared to dissimilar stories. Further, participants with TBI were able to empathise with others despite having markedly reduced autonomic arousal and overall impairment in cognitive functioning.Conclusions: Our results suggest that the PAM has relevance with respect to explaining self-reported empathy for the experiences of others, but cannot explain the role of physiological responses associated with empathy. Further, our results suggest that intact cognitive functioning and physiological responses are not necessary for normal experiences of empathy after TBI.

Understanding how others feel: Evaluating the relationship between empathy and various aspects of emotion recognition following severe traumatic brain injury.

OBJECTIVE: The aim of this study was to use various measures of emotion recognition, such as sensitivity to emotional intensity, accuracy-based emotion labeling, and the ability to differentiate among emotional displays, to examine whether these abilities are associated with emotional and cognitive empathy. We also sought to determine whether these relationships differ between individuals with traumatic brain injury (TBI) and healthy adults. METHOD: TBI participants (n = 28) and healthy adults (n = 29) matched for age, biological sex, and education, were tested on an emotion intensity rating and recognition task. Self-reported emotional and cognitive empathy questionnaires, together with a neuropsychological battery, were also completed. RESULTS: Participants with TBI reported reduced emotional and cognitive empathy. TBI participants also had reduced overall accuracy in recognizing emotion, specifically for happy and sad emotions, although they had no difficulty identifying the intensity or differentiating among emotional displays. Intensity labeling and sensitivity to differentiate among emotions positively correlated with emotional empathy for healthy adults but not for TBI participants. No facet of emotion recognition correlated with cognitive empathy for healthy adults or TBI participants. CONCLUSIONS: The ability to identify the intensity and differentiate among emotions is associated with emotional empathy. Although individuals with severe TBI may be able to differentiate emotions, they may be unable to utilize this information to share and understand the emotions of others, or vice versa. These results could have implications for understanding poor interpersonal relationships and impaired social functioning following TBI. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Subjective emotional experience and physiological responsivity to posed emotions in people with traumatic brain injury.

OBJECTIVE: Although the presence of empathy deficits following traumatic brain injury (TBI) is well established, there is a paucity of research investigating the underpinning mechanisms. This study investigated whether feedback from posed emotional expressions and psychophysiological responsivity, thought to play a role in emotional empathy, are impaired after TBI. METHOD: Thirty adults with TBI and 30 demographically matched healthy controls completed 2 feedback tasks while skin conductance and heart rate were recorded. In Feedback Task 1, participants assumed different emotional postures and rated how this made them feel. In Feedback Task 2, participants held a smile or frown while viewing neutral images and rated the pleasantness of each image. RESULTS: Participants with TBI did not differ from controls in their subjective ratings in response to posed emotional expressions. However, we found reduced skin conductance responses to rapid facial manipulations and some evidence of altered physiological arousal to sad emotional postures in participants with TBI. Finally, there was no relationship between emotional empathy and facial feedback or physiological responsivity. CONCLUSIONS: We failed to replicate past research that demonstrated an impairment in the feedback effect in people with TBI. These normal subjective responses, though, were in the context of reduced psychophysiological responding to the posed expressions, suggesting that another mechanism can contribute to normal feedback effects after TBI. Finally, we did not find the expected relationship between the feedback effect and emotional empathy but may have been limited by the lower than expected rates of low emotional empathy in our sample. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Neurophysiological correlates of visuospatial attention and the social dynamics of gaze processing.

The reflexive orienting response triggered by nonpredictive gaze cues is thought to be driven by a dedicated social neural network responsible for directing attention toward socially salient information. However, atypical processing of eye gaze using concomitant perceptual features has been proposed to underlie attentional orienting in groups with impairments in social cognition. Here, we examined the neurophysiological indices of visuospatial attention during a spatial cueing task, considering individual variability in social cognition in typically developing individuals, and the relative salience of social gaze and perceptual motion cues. We found enhanced neural activation to incongruent cues, wherein modulation of the N2b serves as a marker of the allocation of attention in the spatial domain. Our findings suggest the social gaze cue is less salient for those with greater autistic traits. An attentional bias toward perceptual motion cues correlated with greater social anxiety and alexithymia, and thus may reflect reduced sensitivity to social stimuli. These results provide evidence for likely neurophysiological mechanisms underlying gaze cueing and offer insight into the use of qualitatively different cognitive mechanisms used to access social information. Such paradigms provide potential insight into normative orienting responses reported in atypical groups and would benefit investigations of gaze following abilities in clinical populations.

Preserved rapid conceptual processing of emotional expressions despite reduced neuropsychological performance following traumatic brain injury.

OBJECTIVE: Emotional empathy is critical to successful social interactions and is often compromised after traumatic brain injury (TBI). Using the Emostroop task, we investigated whether adults with moderate to severe TBI (N = 26) have problems with rapid conceptual processing of emotional stimuli compared with controls (N = 30). Further, we investigated whether rapid conceptual processing of emotions relates to emotion recognition and emotional empathy. METHOD: In the Emostroop task, participants categorize emotional words (e.g., joyous, furious, and woeful) into three emotion categories: happy, sad, and angry. Each word is superimposed onto an image of a face, which expresses an emotion that is congruent to the word (congruent condition), incongruent to the word (incongruent condition), or is neutral (neutral condition). Slowed responding in the incongruent condition (interference) and speeded responding in the congruent condition (facilitation) indicates rapid conceptual processing of the faces. Participants also completed an emotion perception task, an empathy questionnaire (the BEES) and neuropsychological tests measuring processing speed, working memory, and executive function. RESULTS: Contrary to our hypotheses, we found that rapid conceptual processing of emotional faces was preserved in people with TBI, despite diminished neuropsychological performance, emotion recognition, emotional empathy, and slowed responding. Further, the Emostroop effect was not correlated with self-reported emotional empathy or with emotion recognition. CONCLUSIONS: We conclude that in people with TBI, reduced empathy may be explained by processes downstream of the initial rapid conceptual processing of emotional information, such as flexibly attending and responding to this information in a goal-directed manner in complex environments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Loss of white matter connections after severe traumatic brain injury (TBI) and its relationship to social cognition.

Adults with severe traumatic brain injury (TBI) often suffer poor social cognition. Social cognition is complex, requiring verbal, non-verbal, auditory, visual and affective input and integration. While damage to focal temporal and frontal areas has been implicated in disorders of social cognition after TBI, the role of white matter pathology has not been examined. In this study 17 adults with chronic, severe TBI and 17 control participants underwent structural MRI scans and Diffusion Tensor Imaging. The Awareness of Social Inference Test (TASIT) was used to assess their ability to understand emotional states, thoughts, intentions and conversational meaning in everyday exchanges. Track-based spatial statistics were used to perform voxelwise analysis of Fractional Anisotropy (FA) and Mean Diffusivity (MD) of white matter tracts associated with poor social cognitive performance. FA suggested a wide range of tracts were implicated in poor TASIT performance including tracts known to mediate, auditory localisation (planum temporale) communication between nonverbal and verbal processes in general (corpus callosum) and in memory in particular (fornix) as well as tracts and structures associated with semantics and verbal recall (left temporal lobe and hippocampus), multimodal processing and integration (thalamus, external capsule, cerebellum) and with social cognition (orbitofrontal cortex, frontopolar cortex, right temporal lobe). Even when controlling for non-social cognition, the corpus callosum, fornix, bilateral thalamus, right external capsule and right temporal lobe remained significant contributors to social cognitive performance. This study highlights the importance of loss of white matter connectivity in producing complex social information processing deficits after TBI.

Facial expressiveness and physiological arousal in frontotemporal dementia: Phenotypic clinical profiles and neural correlates.

Early theories of emotion processing propose an interplay between autonomic function and cognitive appraisal of emotions. Patients with frontotemporal dementia show profound social cognition deficits and atrophy in regions implicated in autonomic emotional responses (insula, amygdala, prefrontal cortex), yet objective measures of facial expressiveness and physiological arousal have been relatively unexplored. We investigated psychophysiological responses (surface facial electromyography (EMG); skin conductance level (SCL)) to emotional stimuli in 25 behavioural-variant frontotemporal dementia (bvFTD) patients, 14 semantic dementia (SD) patients, and 24 healthy older controls, while viewing emotionally positive, neutral, or negative video clips. Voxel-based morphometry was conducted to identify neural correlates of responses. Unlike controls, patients with bvFTD did not show differential facial EMG responses according to emotion condition, whereas SD patients showed increased zygomaticus responses to both positive and neutral videos. Controls showed greater arousal (SCL) when viewing positive and negative videos; however, both bvFTD and SD groups showed no change in SCL across conditions. Regardless of group membership, right insula damage was associated with dampened zygomaticus responses to positive film stimuli. Change in arousal (SCL) was associated with lower integrity of the caudate, amygdala, and temporal pole. Our results demonstrate that while bvFTD patients show an overall dampening of responses, SD patients appear to show incongruous facial emotional expressions. Abnormal responding is related to cortical and subcortical brain atrophy. These results identify potential mechanisms for the abnormal social behaviour in bvFTD and SD and demonstrate that psychophysiological responses are an important mechanism underpinning normal socioemotional functioning.

The role of abnormalities in the corpus callosum in social cognition deficits after Traumatic Brain Injury.

The corpus callosum (CC) is vulnerable to severe traumatic brain injury (TBI). Social cognition requires integration of non-verbal and verbal information in order to understand social behaviour and may be compromised if the CC is damaged. 17 adults with severe, chronic TBI and 17 control participants underwent structural MRI and Diffusion Tensor Imaging. A region of interest analysis examined fractional anisotropy (FA) and mean diffusivity (MD) across regions of the CC. Performance on The Awareness of Social Inference Test (TASIT): part 1 (emotion recognition) and parts 2 and 3 (social inference), was examined in relation to FA and MD. Across participants, higher genu FA values were related to higher TASIT part 3 scores. Increased splenium FA was associated with better performance for TASIT parts 1-3. There was no association between DTI values and TASIT in the controls alone. In the TBI group, FA of the genu and splenium was correlated with TASIT part 3. The pattern of performance was similar when controlling for non-social cognitive ability. In conclusion, social information is complex and multi-modal requiring inter-hemispheric connection. People with TBI, regardless of focal grey matter injury, may lose social cognitive ability due to trauma related changes to the corpus callosum.

The Physiological and Psychological Effects of Ostracism in Adults with ASD.

Whilst some form of ostracism is experienced by most people at some point in their lives, it is experienced far more often in individuals with Autism Spectrum Disorder (ASD). Little is known about how this social exclusion is interpreted, experienced or managed. This study aimed to explore the psychological (mood and social needs) as well as the physiological (arousal) effects of ostracism using a well-established paradigm, Cyberball. Results demonstrated no differences between groups on social needs, however, mood was rated as more negatively by ASDs overall. Arousal was increased in when excluded compared with when excluded for ASDs, but not for controls. Overall, individuals with ASD experienced heightened physiological arousal but whilst these individuals reported overall lower mood, this response to ostracism was not expressed as emotionally significant to these individuals, suggesting possible interoceptive difficulties in this population. This highlights the need for both understanding in non-ASD individuals and intervention of this emotional distress in individuals with ASD.

Ostracism and physiological arousal following traumatic brain injury.

PRIMARY OBJECTIVE: This study aimed to examine the psychological and physiological effects of ostracism in adults with traumatic brain injury (TBI). RESEARCH DESIGN: A within-subject, counterbalanced design was used. The two conditions, inclusion and ostracism, were examined across two groups (between subjects). METHODS AND PROCEDURES: A group of 21 adults with TBI and 17 matched controls participated in the Cyberball paradigm. This task is a computerised task that exposes participants to a game of catch and throw. In the inclusion condition they are included fairly in the game, while in the ostracism condition they are excluded from the game following the first few throws. Skin conductance levels (SCLs) were measured throughout the game as a proxy for social stress. MAIN OUTCOMES: Results showed that people with TBI were cognitively aware of when they are being ostracised, but that their self-reported emotional experience to social exclusion was different to that of the control group. Differences in SCLs between groups and between conditions did not reach significance nor did they correlate with behavioural responses. CONCLUSIONS: These findings are discussed in terms of the consequences of dissociation between psychological and physiological responses and the implications for motivating behaviours associated with re-inclusion.

Not knowing what I feel: Emotional empathy in autism spectrum disorders.

While there is a general consensus in the literature that individuals with autism spectrum disorder have difficulty with cognitive empathy, much less is known about emotional empathy processing in these individuals. Most research has employed subjective self-report measures, which can often be misinterpreted or under-reported/over-reported. More objective measures such as psychophysiological recordings of arousal offer a more objective response. Furthermore, combining physiological responses with self-report ratings allows us to explore the relationship between these two responses to emotionally charged stimuli. A total of 25 individuals with autism spectrum disorder were compared with 25 matched controls on their physiological (arousal) and psychological (self-report) responses to emotionally distressing video scenes. These responses were also then compared with self-report cognitive and emotional trait empathy. Results indicate that while individuals with autism spectrum disorder appear to respond similarly to controls physiologically, their interpretation of this response is dampened emotionally. Furthermore, this dampening of self-report emotional response is associated with a general reduction in trait empathy.

Brain volume loss contributes to arousal and empathy dysregulation following severe traumatic brain injury.

Severe traumatic brain injury (TBI) often leads to deficits in physiological arousal and empathy, which are thought to be linked. This study examined whether injury-related brain volume loss in key limbic system structures is associated with these deficits. Twenty-four adults with TBI and 24 matched Controls underwent MRI scans to establish grey matter volumes in the amygdala, thalamus, and hippocampus. EEG and skin conductance levels were recorded to index basal physiological arousal. Self-report emotional empathy levels were also assessed. The TBI group had reduced brain volumes, topographic alpha differences, and lower emotional empathy compared to Controls. Regional brain volumes were differentially correlated to arousal and self-report empathy. Importantly, lower volume in pertinent brain structures correlated with lower empathy, for participants with and without TBI. Overall we provide new insights into empathic processes after TBI and their relationship to brain volume loss.

Role of Reversal Learning Impairment in Social Disinhibition following Severe Traumatic Brain Injury.

OBJECTIVES: The current study aimed to determine whether reversal learning impairments and feedback-related negativity (FRN), reflecting reward prediction error signals generated by negative feedback during the reversal learning tasks, were associated with social disinhibition in a group of participants with traumatic brain injury (TBI). METHODS: Number of reversal errors on a social and a non-social reversal learning task and FRN were examined for 21 participants with TBI and 21 control participants matched for age. Participants with TBI were also divided into low and high disinhibition groups based on rated videotaped interviews. RESULTS: Participants with TBI made more reversal errors and produced smaller amplitude FRNs than controls. Furthermore, participants with TBI high on social disinhibition made more reversal errors on the social reversal learning task than did those low on social disinhibition. FRN amplitude was not related to disinhibition. CONCLUSIONS: These results suggest that impairment in the ability to update behavior when social reinforcement contingencies change plays a role in social disinhibition after TBI. Furthermore, the social reversal learning task used in this study may be a useful neuropsychological tool for detecting susceptibility to acquired social disinhibition following TBI. Finally, that the FRN amplitude was not associated with social disinhibition suggests that reward prediction error signals are not critical for behavioral adaptation in the social domain.

Reduced heart rate variability in chronic severe traumatic brain injury: Association with impaired emotional and social functioning, and potential for treatment using biofeedback.

Heart rate variability (HRV) may provide an index of capacity for social functioning and may be remediated by HRV biofeedback. Given reductions in HRV are found following traumatic brain injury (TBI), the present study aimed to determine whether lower HRV in TBI is associated with social function, and whether HRV biofeedback might be a useful remediation technique in this population. Resting state HRV and measures of social and emotional processing were collected in 30 individuals with severe TBI (3-34 years post-injury) and 30 controls. This was followed by a single session of HRV biofeedback. HRV was positively associated with social cognition and empathy, and negatively associated with alexithymia for the TBI group. Both TBI and control groups showed significantly increased HRV on both time-domain (i.e., SDNN, rMSSD) and frequency-domain measures (LF, HF, LF:HF ratio) during biofeedback compared to baseline. These results suggest that decreased HRV is linked to social and emotional function following severe TBI, and may be a novel target for therapy using HRV biofeedback techniques.

Goal-directed EEG activity evoked by discriminative stimuli in reinforcement learning.

In reinforcement learning (RL), discriminative stimuli (S) allow agents to anticipate the value of a future outcome, and the response that will produce that outcome. We examined this processing by recording EEG locked to S during RL. Incentive value of outcomes and predictive value of S were manipulated, allowing us to discriminate between outcome-related and response-related activity. S predicting the correct response differed from nonpredictive S in the P2. S paired with high-value outcomes differed from those paired with low-value outcomes in a frontocentral positivity and in the P3b. A slow negativity then distinguished between predictive and nonpredictive S. These results suggest that, first, attention prioritizes detection of informative S. Activation of mental representations of these informative S then retrieves representations of outcomes, which in turn retrieve representations of responses that previously produced those outcomes.

Neurophysiological correlates of dysregulated emotional arousal in severe traumatic brain injury.

OBJECTIVE: This study aimed to elucidate relationships between dysregulated emotional arousal after severe traumatic brain injury (TBI), alpha power and skin conductance levels (SCL), and brain atrophy. METHODS: Nineteen adults with severe TBI and 19 age-, education-, and gender-matched controls (all p's>0.05) participated. Magnetic resonance imaging (MRI) scan established bilateral insulae and amygdale volumes. Mean EEG alpha power and SCLs were recorded simultaneously across four, 2 min conditions: eyes-closed pre-task baseline, view neutral face, happy face and angry face. RESULTS: Scalp-wide alpha suppression occurred from pre-task baseline to the face-viewing conditions (p<.001), but was diminished in TBI (p=.04). TBI participants exhibited marginally significantly lower SCL (p=.051), and elevated alpha power hemispherically, contrasting with controls' midline dominance (p<.01). Significant atrophy was observed in most structures in TBI participants (p's=.004-0.04). Larger left insula, left amygdala and right amygdala correlated positively with alpha power and alpha suppression, and SCLs; all structures uniquely contributed to variance in arousal. CONCLUSIONS: Findings suggest that alpha power provides a sensitive measure of dysregulated emotional arousal post-TBI. Atrophy in pertinent brain structures may contribute to these disturbances. SIGNIFICANCE: These findings have potential implications for the assessment and remediation of TBI-related arousal deficits, by directing more targeted remediation, and better assessing post-TBI recovery.

Automatic facial responses to briefly presented emotional stimuli in autism spectrum disorder.

Emotion processing, including automatic facial mimicry, plays an important role in social reciprocity. Disruptions in these processes have implications for individuals with impaired social functioning, such as autism spectrum disorders (ASDs). Past research has demonstrated that ASDs are impaired in the recognition of briefly presented emotions and display atypical mimicry of emotions presented for protracted duration. Mimicry (electromyography; EMG) of briefly presented emotions was investigated in adults with ASDs. Concurrent measures of skin conductance and cardiac responses were used as markers of orientation and stimulus detection, respectively. A backward masking task was employed whereby the emotional face (happy, angry) was presented for 30 ms followed by a neutral face "mask". An implicit comparison task required rapid gender identification. The ASD group failed to differentiate by valence in their EMG (zygomaticus, corrugator) and demonstrated atypical pre- and post-stimulus arousal. These findings may provide a potential mechanism for marked deficits in social reciprocity.