Alcohol Use Disorder (AUD) is a pervasive and intricate public health challenge, with significant health and psychosocial consequences. Among the most frequently used substances, alcohol provokes diverse neurochemical and neurophysiological changes within the brain and is in long-term excessive use associated with severe cognitive dysfunctions such as memory, decision-making, and problem-solving abilities. This systematic review aims to compare gray matter volume in healthy individuals and those diagnosed with AUD, with the goal of identifying structural differences between the two groups. The six studies, identified from Scopus, Web of Science, and Medline EBSCO, included in this systematic review were written in English, published within the last 20 years, employed magnetic resonance imaging (MRI) to quantify volume, involved human participants over the age of 18, and included both AUD and healthy comparison groups examining gray matter volume differences. The number of participants and gender distribution differed among all the included articles, with two studies exclusively including males. The studies employed either region of interest (ROI) or voxel-based morphometry (VBM) as their analysis method. The results revealed gray matter reductions between individuals with AUD and those without through out the whole brain, both cortical and subcortical, with the most prominent reductions observed in the putamen and thalamus. Future research should consider the limitations presented in this systematic review by conducting longitudinal investigations focusing on gray matter reductions and recovery over extended periods. Such studies could offer deeper insights into how the brain's gray matter volume behaves during longer periods of abstinence among individuals with AUD.

This systematic review explores the complex relationship between depression, dorsolateral prefrontal cortex (DLPFC) activity as measured by functional magnetic resonance imaging (fMRI), and working memory (WM) performance. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a search was conducted on Medline EBSCO and Web of Science databases, specifically targeting peer-reviewed, published papers in English that utilised fMRI. Three studies meeting the inclusion criteria were included. Findings from the included studies yielded conflicting results. Some studies reported hyperactivation in the DLPFC among depressed individuals, suggesting a potential compensatory mechanism to address impairments during WM tasks. Conversely, other studies found no significant differences in DLPFC activity between depressed individuals and healthy controls. Regarding WM performance, studies revealed heterogeneity among depressed individuals compared to controls. While some indicated no significant differences between groups, others highlighted slower performance and decreased accuracy in depressed individuals. This review underscores the necessity for cohesive methodologies to advance understanding of depression-related cognitive impairments. While deficits in WM were observed in individuals with depression, the precise neural correlates of these impairments remain unclear, pointing to possibilities for further research and potential implications for clinical practice.

Post-traumatic stress disorder (PTSD) is a psychiatric disorder that is caused by exposure to traumatic or stressful events in life. 3,4-Methylenedioxymethamphetamine (MDMA) has been shown to be an effective agent in drug-assisted psychotherapy for PTSD. In this systematic review, we aim to evaluate the effect MDMA has on functional connectivity in healthy individuals and individuals with PTSD and investigate the potential mechanisms via which MDMA exerts its effects in MDMA-assisted psychotherapy for PTSD patients. A total of 134 articles from Web of Science and Medline EBSCO were screened and 5 articles relevant for the systematic review were identified. After MDMA administration, an increase and decrease in functional connectivity in multiple brain areas and networks was observed, such as the thalamus, visual cortex, anterior cingulate cortex, hippocampus, amygdala, prefrontal cortex, default mode network, cerebellar network, sensorimotor network, salience network, and executive network. Notably, MDMA increased amygdala-hippocampal functional connectivity which may link to improved emotion regulation and fear extinction in patients receiving MDMA-assisted therapy. The findings evidence the complex effects of MDMA on brain connectivity and highlight the need for further research in this area, although MDMA-assisted therapy does prove to be a promising alternative for treating PTSD.

The neural code from the inner ear to the brain is dynamically controlled by central nervous efferent feedback to the audio-vestibular epithelium. Although such efference provides the basis for a cognitive control of our hearing and balance, we know surprisingly little about this feedback system. This project has investigated the applicability of a transgenic mouse model, expressing a fluorescent protein under the choline-acetyltransferase (ChAT) promoter, for targeting the cholinergic audio-vestibular efferent neurons in the brainstem. It was found that the mouse model is useful for targeting the vestibular efferents, which are fluorescent, but not the auditory efferents, which are not highlighted. This model enables, for the first time, physiological studies of the vestibular efferent neurons and their synaptic inputs. We next assessed the expression of the potassium channel family Kv4, known to generate transient potassium currents upon depolarization. Such potassium currents are found in auditory efferent neurons, but it is not known whether Kv4 subunits are expressed in these neurons. Moreover, it is not known if Kv4 is present and has a function in the vestibular efferent neurons. Double labelling with anti-ChAT and anti-Kv4.2 or Kv4.3 demonstrates that the Kv4.3 subunits are abundantly expressed in audio-vestibular efferents, thus indicating that this subunit is a large contributor to the excitability and firing properties of the auditory efferent neurons, and most probably also for the vestibular efferent neurons. In addition, we also unexpectedly found a strong expression of Kv4.3 in principal cells of the superior olive, the neurons which are important for sound localization.

Background: Despite our distinct impression to the contrary, we are only conscious of a fraction of all the neural activity underlying our thoughts and behavior. Most neural processes occur non-consciously, and in parallel with our conscious experience. However, it is still unclear what the limits of non-conscious processes are in terms of higher cognitive functions. Many recent studies have shown that increasingly more advanced functions can operate non-consciously, but non-conscious information is still thought to be fleeting and undetectable within 500 milliseconds. Here we used various techniques to render information non-conscious, together with functional magnetic resonance imaging (fMRI), to investigate if non-consciously presented information can be retained for several seconds, what the neural substrates of such retention are, and if it is consistent with working memory maintenance. Results: In Study I we used an attentional blink paradigm to render stimuli (single letters) non-conscious, and a variable delay period (5 – 15 s) prior to memory test. It was found that non-conscious memory performance was above chance after all delay durations, and showed no signs of decline over time. Univariate fMRI analysis showed that the durable retention was associated with sustained BOLD signal change in the prefrontal cortex and cerebellum during the delay period. In Study II we used continuous flash suppression (CFS) to render stimuli (faces and tools) non-conscious, and a variable delay period (5 or 15 s) prior to memory test. The durable retention of up to 15 s was replicated, and it was found that stimuli identity and spatial position was retained until prospective use. In Study III we used CFS to render tools non-conscious, and a variable delay period (5 – 15 s) prior to memory test. It was found that memory performance was not better than chance. However, by using multi-voxel pattern analysis it was nonetheless possible to detect the presence vs. absence of non-conscious stimuli in the frontal cortex,and their spatial position (left vs. right) in the occipital cortex during the delay. Conclusions: Overall these findings suggest that non-consciously presented information (identity and/or position) can be retained for several seconds,and is associated with BOLD signal in frontal and posterior regions. These findings are consistent with working memory maintenance of non-consciously presented information, and thereby constrain models of working memory and theories of consciousness.

The circadian rhythm is a rhythm which permeates all aspects of biological life and follows the hours of the sun. The pace of the rhythm is controlled by a collection of neurons in the hypothalamus, called the suprachiasmatic nucleus (SCN), whose signals affect rhythms throughout the body as can be seen in aspects of life from behavior down to oscillations of proteins in the cells. A disruption of this rhythm such as what happens during jet lag, where the rhythm of the SCN is out of synch with the rhythm of the rest of the body, is something that can have adverse effects on mental and physical health. To realign the SCN and the rhythm of the body, different methods and be implemented. This thesis investigated the effectiveness of glucocorticoids on re-aligning the rhythms of the body following a disruption through a meta-analysis and a qualitative review. The meta-analysis and review incorporated experiments from six articles investigating the hours of circadian rhythm shifts in the mouse model, after administering glucocorticoids. What was found was that the individual experiments presented results with high effect sizes; however, the direction of said effects was not uniform as the rhythms shifted in different directions. The lack of uniform direction caused no significant combined effect size to be found by this meta-analysis (MES=0.11 ± 0.06), showing that a statistical analysis based on hours shifted could not find a significant combined effect. The qualitative review, however, indicates that the administration of glucocorticoids shows an effect in re-entraining the rhythm of the peripheral parts of the body to that of the environmental cues and the SCN. Though no significant statistical effect was found in this analysis, the effect of glucocorticoids should not be discounted and could still prove a promising treatment for circadian disruptions, such as jet lag.

The relationship between personality trait change and major life events is currently undergoing extensive investigations within the field of personality psychology. A debate has risen regarding whether or not major life events can bring about trait change, and how typical trait change patterns over the adult lifespan can be explained. It is valuable to understand how traits change because they predict important future outcomes. The Five-Factor Theory described by McCrae and Costa (2008a) states that traits are purely biological entities, and trait change is explained to result from processes of intrinsic biological maturation, unaffected by life events. This thesis reviewed the literature regarding the relationship of trait change and life events, and the research of potential biological bases of traits in the brain together with a brain developmental perspective of intrinsic maturation. Gaining an insight in the relationship between personality traits and the brain is a goal within a young field of research called personality neuroscience, and an agenda of the Five-Factor Theory. Major life events do cause trait change, but the relationship is complex. A brain developmental perspective of intrinsic maturation did not entirely correspond with patterns of typical trait change in young adulthood. The Five-Factor Theory is challenged and modifications are suggested. Neurobiological correlates of five-factor traits reveal issues and potentials for future research.

The Mediterranean diet (Medi) has been highlighted as the golden diet rich in protective properties associated with cognitive- and emotional health. The foundation of the Medi comprises vegetables, fruits, nuts and seeds, legumes, and extra virgin olive oil. Research has been conducted in both holistic dietary approach and single nutrient approach regarding the impact of nutrition and diet, in this case, the Medi‟s effect on brain health. This review aims to give an up to date overview of the Mediterranean diet, outline some of the diet's abundant nutrients, and discuss studies linking the nutrient's potential effect on depression, cognitive decline, dementia, and brain structure and function. In addition, this review will attempt to assess whether the Medi as a whole or if a single nutrient approach is accountable for the health-promoting findings. Furthermore, the gut-brain axis, and other potential underlying mechanisms involved in the modulation of food- and nutrient intake and their effects on the brain, will be outlined. A diet high in fruit-, vegetable-, polyunsaturated fatty acid-, and monounsaturated fatty acid content has great power for health-maintenance and decreases the risk of suffering cognitive decline, dementia, and potentially depression. More randomized controlled trials are however eagerly awaited to give more substance to previous findings.

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 pro-inflammatory 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.

Self-determination theory (SDT), a motivation theory, consists of motivation types: intrinsic motivation, extrinsic motivation, and amotivation, where the social environment is important. SDT’s motivation orientations are about individual differences in people’s tendencies to orient towards environments. The five factor model (FFM), a personality theory, consists of five factors and can be grouped into two metatraits; plasticity: extraversion and openness; and stability: agreeableness, conscientiousness, and neuroticism. Studies show that SDT’s motivation orientations and the factors of FFM significantly covary. Intrinsic motivation and trait plasticity have similar features; the desire for exploration, engagement, well-being, and dopamine as neural correlate. The thesis reviews the role of dopamine as the neural correlate of intrinsic motivation and trait plasticity – a relation between motivation and personality. Dopamine and trait plasticity function to attain rewards of uncertainty and explore, but uncertainty is threatening. Salience coding neurons, value coding neurons and a combination of both are related, respectively, to rewards of information, specific rewards and the value of any uncertainty. Intrinsic motivation is related to the value coding neurons, flow via D2 receptors, the salience network, and the seeking system. Conclusions: there are many appealing similarities and rational that relate constructs/mechanisms – motivation is related to personality; can there even be a common construct? However; results based on proposed theories, neuroscientific quality issues, early inconsistent findings of intrinsic motivation mechanisms, and trait stability are speculated to, also, be needed to model intrinsic motivation. Unifying cross-disciplinary work and proposed theories of neural correlates are encouraged.