Neurophysiological Biomarkers of Persistent Post-concussive Symptoms: A Scoping Review

Background and Objectives: Persistent post-concussive symptoms (PCS) consist of neurologic and psychological complaints persisting after a mild traumatic brain injury (mTBI). It affects up to 50% of mTBI patients, may cause long-term disability, and reduce patients' quality of life. The aim of this review was to examine the possible use of different neuroimaging modalities in PCS.Methods: Articles from Pubmed database were screened to extract studies that investigated the relationship between any neuroimaging features and symptoms of PCS. Descriptive statistics were applied to report the results.Results: A total of 80 out of 939 papers were included in the final review. Ten examined conventional MRI (30% positive finding), 24 examined diffusion weighted imaging (54.17% positive finding), 23 examined functional MRI (82.61% positive finding), nine examined electro(magneto)encephalography (77.78% positive finding), and 14 examined other techniques (71% positive finding).Conclusion: MRI was the most widely used technique, while functional techniques seem to be the most sensitive tools to evaluate PCS. The common functional patterns associated with symptoms of PCS were a decreased anti-correlation between the default mode network and the task positive network and reduced brain activity in specific areas (most often in the prefrontal cortex).Significance: Our findings highlight the importance to use functional approaches which demonstrated a functional alteration in brain connectivity and activity in most studies assessing PCS.

Dynamic switching between intrinsic and extrinsic mode networks as demands change from passive to active processing

In this study we report on the relationship between default and extrinsic mode networks across alternating brief periods of rest and active task processing. Three different visual tasks were used in a classic fMRI ON–OFF block design where task (ON) blocks alternated with equal periods of rest (OFF) blocks: mental rotation, working memory and mental arithmetic. We showed the existence of a generalized task-positive network, labelled the extrinsic mode network (EMN) that is anti-correlated with the default mode network (DMN) as processing demands shifted from rest to active processing. We then identified two key regions of interest (ROIs) in the supplementary motor area (SMA) and precuneus/posterior cingulate cortex (PCC) regions as hubs for the extrinsic and intrinsic networks, and extracted the time-course from these ROIs. The results showed a close to perfect anti-correlation for the SMA and Precuneus/PCC time-courses for ON- and OFF-blocks. We suggest the existence of two large-scale networks, an extrinsic mode network and an intrinsic mode network, which are up- and down-regulated as environmental demands change from active to passive processing.

What executive function network is that? An image-based meta-analysis of network labels

The current state of label conventions used to describe brain networks related to executive functions is highly inconsistent, leading to confusion among researchers regarding network labels. Visually similar networks are referred to by different labels, yet these same labels are used to distinguish networks within studies. We performed a literature review of fMRI studies and identified nine frequently-used labels that are used to describe topographically or functionally similar neural networks: central executive network (CEN), cognitive control network (CCN), dorsal attention network (DAN), executive control network (ECN), executive network (EN), frontoparietal network (FPN), working memory network (WMN), task positive network (TPN), and ventral attention network (VAN). Our aim was to meta-analytically determine consistency of network topography within and across these labels. We hypothesized finding considerable overlap in the spatial topography among the neural networks associated with these labels. An image-based meta-analysis was performed on 166 individual statistical maps (SPMs) received from authors of 72 papers listed on PubMed. Our results indicated that there was very little consistency in the SPMs labeled with a given network name. We identified four clusters of SPMs representing four spatially distinct executive function networks. We provide recommendations regarding label nomenclature and propose that authors looking to assign labels to executive function networks adopt this template set for labeling networks.

Representation Learning of Resting State fMRI with Variational Autoencoder

Resting state functional magnetic resonance imaging (rs-fMRI) data exhibits complex but structured patterns. However, the underlying origins are unclear and entangled in rs-fMRI data. Here we establish a variational auto-encoder, as a generative model trainable with unsupervised learning, to disentangle the unknown sources of rs-fMRI activity. After being trained with large data from the Human Connectome Project, the model has learned to represent and generate patterns of cortical activity and connectivity using latent variables. Of the latent representation, its distribution reveals overlapping functional networks, and its geometry is unique to each individual. Our results support the functional opposition between the default mode network and the task-positive network, while such opposition is asymmetric and non-stationary. Correlations between latent variables, rather than cortical connectivity, can be used as a more reliable feature to accurately identify subjects from a large group, even if only a short period of data is available per subject.

Emotional awareness amongst middle leadership

PurposeThe purpose of this viewpoint paper is to explore middle leaders' ability to recognise emotions in the context of workplace research, and to propose measures that might support them in their role.Design/methodology/approachThis paper combines a contemporary literature review with reflections from practice to develop more nuanced understandings of middle leadership. This paper applied the Geneva Emotional Recognition Test (GERT) to explore the level of emotional recognition of 86 individuals (teachers to headteachers (equivalent to school principals)).FindingsThe preliminary findings suggest that teachers and headteachers have higher levels of emotional recognition than middle and senior leaders. This paper subsequently argues that the task-orientated nature middle leadership compounds an individual's ability to engage effectively in relationship-orientated tasks. This explains why middle leaders scored lower on the GERT assessment. This is further inhibited by the anti-correlation in the brain's ability to deal with the task-positive network (TDM) and default mode network (DMN) processing functions where individuals operate in one neural mode for long periods.Research limitations/implicationsThe viewpoint paper proposes a number of implications for middle leaders and suggests that middle leaders should proactively seek out opportunities to be engaged in activities that support the DMN function of the brain and subsequently the relationship-orientated aspects of leadership, for example, coaching other staff members. However, it has to be recognised that the sample size is small and further work is needed before any generalisations can be made.Originality/valueThis paper offers a contemporary review of the role of middle leaders underpinned by a preliminary study into individuals' ability to recognise emotions.

0079 Blue Light Exposure Enhances Neural Efficiency of the Task Positive Network During a Cognitive Interference Task

Introduction Light exposure has powerful effects on the circadian timing of sleep and wake, primarily through the regulation of the secretion of melatonin. However, it is becoming clear that light has additional alerting effects beyond its primary effect on the circadian system. Exposure to light, particularly blue-wavelength light, has been shown to acutely increase brain activation, alertness, and some elementary aspects of cognitive performance such as working memory and emotional anticipation during the day. Whether blue light exposure can have longer-lasting effects on brain activation and performance during more complex cognitive control tasks up to 30-minutes after light cessation is unknown. Methods In a sample of 30 healthy adults, we examined the effects of a single 30-minute exposure to either blue (n=14) or amber placebo (n=16) light on subsequent brain activation and performance during the Multi-Source Interference Task (MSIT) measured a half-hour after light cessation using functional magnetic resonance imaging. Mean activation in all regions showing increased task-related activation (i.e., Task Positive Network; TPN) and regions showing decreased activation (i.e., Default Mode Network; DMN) at p<.001 (FWE corrected) was extracted separately for each network in SPM12 and compared between light conditions. Results Performance metrics for the MSIT, including accuracy, response time, and cognitive throughput, did not differ between the blue and amber conditions, suggesting that performance was sustained equally between light conditions. However, brain activation within the TPN to the interference condition of the MSIT was significantly lower (p=.024) in the blue relative to the amber condition, with no group differences observed for suppression of the DMN. Conclusion Compared to amber, a single exposure to blue light was associated with enhanced neural efficiency a half-hour later as demonstrated by reduced TPN activation to achieve the same level of cognitive performance. Blue light may be an effective method for optimizing neurocognitive performance under some conditions. Support US Army Medical Research and Materiel Command: W81XWH-14-1-0571

M141. INDIVIDUALS WITH SCHIZOTYPAL TRAITS SHOW A UNIQUE PATTERN OF CAUDATE ACTIVATION IN PROSPECTION OF POSITIVE EMOTION COMPARED TO HEALTHY CONTROLS

Background Prospection, the ability to simulate future scenarios and pre-experience future feelings, plays a fundamental role in anhedonia and motivation. Empirical findings have suggested that a wide range of patients who experience anhedonia, with schizophrenia, autism and major depression, exhibit prospection impairment. Altered brain responses while envisioning future events have also been observed in these clinical samples. However, it remains unclear whether similar abnormalities are exhibited by individuals with schizotypal traits (ST), autistic traits (AT) and subsyndromal depressive symptoms (SD). Methods The Schizotypal Personality Questionnaire, Autism-Spectrum Quotient, and Patient Health Questionnaire-9 were administered to a group of 2904 college students. Based on the cut-off points of each scale, a final sample of 27 individuals with ST, 34 with AT, 31 with SD, and 35 with low levels of all subclinical features (controls) were recruited. Participants performed a Prospection Task in a 3T MRI scanner and completed the Temporal Experience of Pleasure Scale (TEPS) after the brain scan. The Prospection task included three conditions: positive prospection, neutral prospection, and control imagination. Contrasts examining general prospection [positive prospection + neutral prospection – control imagination], positive prospection [positive prospection- control imagination], neutral prospection [neutral prospection-control imagination], and positive emotion [positive prospection – neutral prospection] were defined. Group comparisons were conducted to measure brain activation in all contrasts using a threshold of p<0.001, Familywise error corrected. Results Increased activation of the task-positive network, including regions of the bilateral inferior parietal gyrus, the middle frontal gyrus, and the inferior frontal gyrus, was observed in individuals with ST, AT and SD, for the general prospection contrast, compared to controls. Both individuals with ST and AT exhibited reduced activation of the medial frontal gyrus, the posterior cingulate cortex, the precuneus, and the hippocampus (the “core network”/default mode network) for the general prospection contrast, compared to controls. However, only individuals with ST exhibited increased activation of the bilateral caudate for the positive emotion contrast. Moreover, activation of the bilateral caudate in ST individuals was negatively correlated with the contextual anticipatory pleasure subscale of the TEPS (r=-0.215, p=0.019). Discussion Our findings showed that individuals with ST, AT and SD exhibited increased activation of the task-positive network, suggesting that these individuals might mobilize more cognitive effort to envision future events compared with controls. Moreover, the findings of decreased activation in the “core network” observed in individuals with ST and AT further suggests that only these individuals, but not those with SD, have prospection impairment. On the other hand, only individuals with ST exhibited hyper-activation of the caudate, thalamus, and claustrum for the positive emotion contrast. These findings suggest that individuals with ST demonstrate a distinct pattern of brain activation while prospecting future events.