The immune system has been suggested as crucial in brain and psychological functioning. More precisely, immune markers reflecting immune system activity are important for psychological and mental health, as evident by their role in the physiopathology of depression and in the impairment of executive functions. Frontal alpha asymmetry (FAA), an electroencephalographic marker of brain function, has also been linked to such psychopathology and is thought to reflect psychological processes underlying approach- versus withdrawal-related motivation and higher-order inhibitory control. Only a few studies have linked FAA to immune markers but notably found a negative association between IL-6, a pleiotropic proinflammatory cytokine, and FAA. The aim of the present work is thus to study the relationship between various immune markers (including pro-inflammatory cytokines and IL-6) and FAA. 35 healthy young male participants underwent a resting EEG recording and blood sampling from which immune markers were measured. The results did not suggest an association between IL-6 and FAA. No other immune markers were either suggested to be associated to FAA. The complexity of the immune system (e.g., effect of cytokines) is underlined and may explain the results. Despite such results, the implication of true negative correlations between FAA and circulating immune markers, as suggested in previous studies, is discussed in the light of the theoretical models of FAA.

The overall aim of the present thesis is to clarify the control of intracellular chloride homeostasis in central neurons, because of the critical role of chloride ions (Cl–) for neuronal function. Normal function of the central nervous system (CNS) depends on a delicate balance between neuronal excitation and inhibition. Inhibition is, in the adult brain, most often mediated by the neurotransmitter γ-aminobutyric acid (GABA). GABA may, however, in some cases cause excitation. GABA acts by activating GABA type A receptors (GABAARs), which are ion channels largely permeable to Cl–. The effect of GABAAR-mediated neuronal signaling - inhibitory or excitatory - is therefore mainly determined by the Cl– gradient across the membrane. This gradient varies with neuronal activity and may be altered in pathological conditions. Thus, understanding Cl– regulation is important to comprehend neuronal function. This thesis is an attempt to clarify several unknown aspects of neuronal Cl– regulation. For such clarification, a sufficiently sensitive method for measuring the intracellular Cl– concentration, [Cl–]i, is necessary. In the first study of this thesis, we examined two electrophysiological methods commonly used to estimate [Cl–]i. Both methods, here called the interpolation and the voltage-ramp method, depend on an estimate of the Cl– equilibrium potential from the current-voltage relation of GABA- or glycine-evoked Cl– currents. Both methods also provide an estimate of the membrane Cl– conductance, gCl. With a combination of computational and electrophysiological techniques, we showed that the most common (interpolation) method failed to detect changes in [Cl–]i and gCl during prolonged GABA application, whereas the voltage-ramp method accurately detected such changes. Our analysis also provided an explanation as to why the two methods differ. In a second study, we clarified the role of the extracellular matrix (ECM) for the distribution of Cl– across the cell membrane of neurons from rat brain. It was recently proposed that immobile charges located within the ECM, rather than as previously thought cation-chloride transporter proteins, determine the low [Cl–]i which is critical to GABAAR-mediated inhibition. By using electrophysiological techniques to measure [Cl–]i, we showed that digestion of the ECM decreases the expression and function of the neuron-specific K+ Cl– cotransporter 2 (KCC2), which normally extrudes Cl- from the neuron, thus causing an increase in resting [Cl–]i. As a result of ECM degradation, the action of GABA may be transformed from inhibitory to excitatory. In a third study, we developed a method for quantifying the largely unknown resting Cl– (leak) conductance, gCl, and examined the role of gCl for the neuronal Cl– homeostasis. In isolated preoptic neurons from rat, resting gCl was about 6 % of total resting conductance, to a major part due to spontaneously open GABAARs and played an important role for recovery after a high Cl– load. We also showed that spontaneous, impulse-independent GABA release can significantly enhance recovery when the GABA responses are potentiated by the neurosteroid allopregnanolone. In a final commentary, we formulated the mathematical relation between Cl– conductance, KCC2-mediated Cl– extrusion capacity and steady-state [Cl–]i. In summary, the present thesis (i) clarifies how well common electrophysiological methods describe [Cl–]i and gCl, (ii) provides a novel method for quantifying gCl in cell membranes and (iii) clarifies the roles of the ECM, ion channels and ion transporters in the control of [Cl–]i homeostasis and GABAAR-mediated signaling in central neurons.

Epilepsy is the most common, chronic, serious neurological disease in the world, with an estimated 65 million people affected worldwide. Recent studies on people diagnosed with epilepsy suggest that stress might trigger epileptic seizures. Interventions aimed at lowering stress might be able to reduce the risk for epileptic seizures among epileptics. In an attempt to explore this possibility, I conducted a systematic review addressing the efficacy of behavioral interventions targeted at lowering stress on seizure frequency among an epileptic population. This article also investigated the efficacy of these interventions on lowering self-perceived stress in the same population. Three databases were searched for obtaining 54 references. After a systematic filtering process, a set of 2 studies was retained after the full search procedure. The results suggest stress-reducing behavioral interventions do not have any statistically significant effects on lowering seizure frequency but have a statistically significant effect on lowering self-perceived stress ratings among an epileptic population. The small but promising results from trials and systematic reviews not included in this review warrant further research into the topic. Limitations regarding search procedure included studies and consideration for further research and reading for the presented topics are discussed.

Sammanfattning Bakgrund: Studier tyder på bristande kunskaper angående hanteringen av idrottsrelaterad hjärnskakning samt i rehabilitering efteråt. Ryttares återgång till fysisk aktivitet kopplat med en jargong som främjar en för snabb återgång, där saknas studier.  Syfte: Att undersöka och beskriva en grupp tävlingsryttares upplevelser och erfarenheter av att ha fått en idrottsrelaterad hjärnskakning samt återgången till sin idrott, vardagsliv samt fysisk aktivitet. Metod: Data från fem informanter insamlades via semistrukturerade intervjuer och har analyserats med en innehållsanalys. Resultat: I studien framgick det två teman; “Hur IH yttrade sig och påverkade vardagen” samt “Vägen tillbaka” med totalt tio kategorier samt 16 subkategorier. Utifrån resultatet framgick det brister i adekvat information vid vårdtillfället rörande återgång till fysisk aktivitet efter idrottsrelaterad hjärnskakning. Omgivningens reaktioner påverkade ryttarna initialt till en något långsammare återgång till fysisk aktivitet, samtidigt som de egna kraven på skötsel av hästen fanns ständigt närvarande. Konklusion: Studien tyder på att återgången fortfarande går för snabbt men att omgivningens påverkan, i kombination med egen förståelse samt att den tidigare jargongen börjat avta har lett till en långsammare återgång. Dock finns kvarvarande brister angående information kring hur återgången bör ske efter en idrottsrelaterad hjärnskakning inom vården. / Abstract Background: Studies indicate a lack of knowledge regarding the handling of the acute state of sport related concussion and during the rehabilitation afterwards. Equestrians return to physical activity associated with a jargon that promotes an over-rapid return, where studies are lacking. Purpose: To investigate and describe a group of competing equestrians experiences of receiving a suspected or diagnosed sport related concussion and also their return to sport, everyday life and physical activity. Method: Data from five informants were collected through semi structured interviews and analysed with a content analysis. Results: The study showed two themes; “How SRC expressed and influenced everyday life” and “The way back” with a total of ten categories and 16 subcategories. Based on the result, there were shortcomings in adequate information from the time of health care treatment regarding the return to physical activity after a sport related concussion. The society's reaction initially affected the riders to a slower return to physical activity, while the own requirements for taking care of the horse were constantly present. Conclusion: The study indicates that their return still goes on too quick, but the surroundings effects, in combination with their own understanding and that the previous jargon has begun to decline has led to a slower return. However, there are remaining deficiencies regarding the information about how the return should take place after a sport related concussion within the healthcare system.

The somatosensory system concerns the sense of touch. It is sectioned into various kinds of touch, such as the proprioceptive sense, providing information of sense of self and position of limbs, and the cutaneous sense, informing of the modalities of touching or being touched. The cutaneous sense is further divided into discriminative touch and affective touch. Discriminative touch is an exteroceptive sense of touch that responds to stimuli of pressure and vibration, and affective touch is an interoceptive sense of touch that corresponds to e.g. pleasant and painful stimuli, communicating information to the brain through A-delta and C-fibers. Recent studies investigates affective touch to have emotional affect on the subjective experience of touch, affecting subjective wellbeing. The aim of this thesis is to examine the sense of touch and its relevant neural correlates, focusing on affective touch and its role in subjective wellbeing and social relations. A presentation of physiological and neural aspects of touch will be held as well as a description of subjective wellbeing. The conclusion for this thesis is that affective touch appears to activate brain areas of orbitofrontal cortex, frontal polar cortice, prefrontal cortex and insula cortex, which are brain areas processing subjective wellbeing, e.g. evaluating positive and negative effect and processing emotional information and behavior. Examining correlations between affective touch and positive affect, negative affect, oxytocin release, social relations and affiliative behavior shows influence from affective touch on subjective wellbeing. A discussion of the current findings is provided, including directions for future research.

The somatosensory system concerns the sense of touch. It is sectioned into various kinds of touch, such as the proprioceptive sense, providing information of sense of self and position of limbs, and the cutaneous sense, informing of the modalities of touching or being touched. The cutaneous sense is further divided into discriminative touch and affective touch. Discriminative touch is an exteroceptive sense of touch that responds to stimuli of pressure and vibration, and affective touch is an interoceptive sense of touch that corresponds to e.g. pleasant and painful stimuli, communicating information to the brain through A-delta and C-fibers. Recent studies investigates affective touch to have emotional affect on the subjective experience of touch, affecting subjective wellbeing. The aim of this thesis is to examine the sense of touch and its relevant neural correlates, focusing on affective touch and its role in subjective wellbeing and social relations. A presentation of physiological and neural aspects of touch will be held as well as a description of subjective wellbeing. The conclusion for this thesis is that affective touch appears to activate brain areas of orbitofrontal cortex, frontal polar cortice, prefrontal cortex and insula cortex, which are brain areas processing subjective wellbeing, e.g. evaluating positive and negative effect and processing emotional information and behavior. Examining correlations between affective touch and positive affect, negative affect, oxytocin release, social relations and affiliative behavior shows influence from affective touch on subjective wellbeing. A discussion of the current findings is provided, including directions for future research.

Two decades of event-related potential (ERP) research have established that the most consistent correlates of the onset of visual consciousness are the early visual awareness negativity (VAN), a negative component in the N2 time range over posterior electrode sites, and the late positivity (LP), a positive component in the P3 time range over fronto-parietal electrode sites. A review by Koivisto & Revonsuo (2010) had looked at 39 studies and concluded that the VAN is the earliest and most reliable correlate of visual phenomenal consciousness, whereas the LP probably reflects later processes associated with reflective/access consciousness. However, an “early” vs. “late” debate still persists. This thesis provides an update to that earlier review. All ERP and MEG studies that have appeared since 2010 and directly compared ERPs of aware and unaware conditions are considered. The result corroborates the view that VAN is the earliest and most consistent signature of visual phenomenal consciousness, and casts further doubt on the LP as an ERP correlate of consciousness. Important new methodological, empirical, and theoretical developments in the field are described, and the empirical results are related to the theoretical background debates.

Over the years stress has been a term lacking one clear and specific definition. In general, the term stress has been used mostly as an explanation of a response or reaction to a stressor. A stressor can be of both physiological and behavioral character. The experience of stress can occur both due to a real or a perceived stressor. In this literature review, the concept of stress is viewed with insights from biological, psychological, and social perspectives. The stress response is described biologically with the central nervous system (CNS), the brain, and the hypothalamic-pituitary-adrenal (HPA) axis. Social and psychological stress are concepts related to how stress is perceived by the mind and due to social surroundings which is described in relation to social support, self-efficacy, the locus of control and cognitive appraisal. Dealing with stress can be done through coping which refers to the individual capacity to handle a stressor and has generally been divided into two categories, active/passive coping and problem-focused/emotion-focused coping. Depending on the individual resources to cope with a stressor and the ability to decrease the stress response when needed, the long-term effects of stress can therefore vary between individuals. It has been found that positive coping (known as reducing stress) can increase the anterior cingulate cortex (ACC) volume and decrease anxiety and depression. The prefrontal cortex (PFC), the hippocampus, and the amygdala are closely linked to the ACC and affect emotions, learning, and memory related to the stress response.

Conflicts are part of our everyday life and the field of psychology describes how specific personality traits relate to specific conflict styles. However, the question remaining is why these relations exist? Recently, personality neuroscience has begun pinning down the neurobiology of personality traits, providing a deeper understanding of the human behavior. The present thesis utilizes the Five Factor Model (FFM; Costa & McCrae, 1990) of personality to investigate the neurobiology underlying the inverse relation between the specific personality trait of Agreeableness and dominating conflict style (a conflict management style characterized by aggressiveness, authoritarianism and/or need for dominance). Agreeableness overlaps both empathy and aggression which can work as each other’s opposites in explaining conflict behaviors. The goal of the thesis was to investigate whether the inverse relation between Agreeableness and dominating conflict style can be explained by brain regions. Brain regions such as the medial prefrontal cortex and regions involving anterior cingulate appear to be the most prominent neurobiology describing the relation. Serotonin is the neural substance involved in most cortical and subcortical brain structures and it also regulates the suppression of aggression, making it an important substance both within Agreeableness and the preference for dominating conflict style. The thesis will sum up with a discussion including some limitations within the research and further aspects such the consequences of the findings will be discussed.

Brain-computer interfaces (BCIs) blend methods and concepts researched by cognitive neuroscience, electrophysiology, computer science and engineering, resulting in systems of bi-directional information exchange directly between brain and computer. BCIs contribute to medical applications that restore communication and mobility for disabled patients and provide new forms of sending information to devices for enhancement and entertainment. Virtual reality (VR) introduces humans into a computer-generated world, tackling immersion and involvement. VR technology extends the classical multimedia experience, as the user is able to move within the environment, interact with other virtual participants, and manipulate objects, in order to generate the feeling of presence. This essay presents the possibilities of merging BCI with VR and the challenges to be tackled in the future. Current attempts to combine BCI and VR technology have shown that VR is a useful tool to test the functioning of BCIs, with safe, controlled and realistic experiments; there are better outcomes for VR and BCI combinations used for medical purposes compared to solely BCI training; and, enhancement systems for healthy users seem promising with VR-BCIs designed for home users. Future trends include brain-to-brain communication, sharing of several users’ brain signals within the virtual environment, and better and more efficient interfaces.