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  1. Article: Glutamate in Salience Network Predicts BOLD Response in Default Mode Network During Salience Processing

    Walter, Martin

    Frontiers in behavioral neuroscience, 13:232

    2019  

    Abstract: BACKGROUND: Brain investigations identified salience network (SN) comprising the dorsal Anterior Cingulate Cortex (dACC) and the Anterior Insula (AI). Magnetic resonance spectroscopy (MRS) studies revealed the link between the glutamate concentration in ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract BACKGROUND: Brain investigations identified salience network (SN) comprising the dorsal Anterior Cingulate Cortex (dACC) and the Anterior Insula (AI). Magnetic resonance spectroscopy (MRS) studies revealed the link between the glutamate concentration in the ACC and alterations in attentional scope. Hence, we investigated whether glutamate concentration in the dACC modulates brain response during salience processing. METHODS: Twenty-seven healthy subjects (12♀, 15♁) provided both STEAM MRS at 7T measuring glutamate concentrations in the dACC as well as a functional magnetic resonance imaging (fMRI) task to study the influence on content-related salience processing and expectedness. Salience was modulated for both sexual and non-sexual emotional photos in either expected or unexpected situations. Correlation between MRS and task fMRI was investigated by performing regression analyses controlling for age, gender, and gray matter partial volume. RESULTS/CONCLUSION: During picture processing, the extent of deactivation in the Posterior Cingulate Cortex (PCC) was attenuated by two different salience attributions: sexual content and unexpectedness of emotional content. Our results indicate that stimulus inherent salience induces an attenuation of the deactivation in PCC, which is in turn balanced by higher level of glutamate in the dACC.
    Keywords MRS ; PCC ; attention ; glutamate ; fMRI ; salience attribution
    Language English
    Document type Article
    Database Repository for Life Sciences

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  2. Article: Serotonergic, Dopaminergic, and Noradrenergic Modulation of Erotic Stimulus Processing in the Male Human Brain

    Walter, Martin

    Journal of Clinical Medicine, 8(3):363

    2019  

    Abstract: Human sexual behavior is mediated by a complex interplay of cerebral and spinal centers, as well as hormonal, peripheral, and autonomic functions. Neuroimaging studies identified central neural signatures of human sexual responses comprising neural ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract Human sexual behavior is mediated by a complex interplay of cerebral and spinal centers, as well as hormonal, peripheral, and autonomic functions. Neuroimaging studies identified central neural signatures of human sexual responses comprising neural emotional, motivational, autonomic, and cognitive components. However, empirical evidence regarding the neuromodulation of these neural signatures of human sexual responses was scarce for decades. Pharmacological functional magnetic resonance imaging (fMRI) provides a valuable tool to examine the interaction between neuromodulator systems and functional network anatomy relevant for human sexual behavior. In addition, this approach enables the examination of potential neural mechanisms regarding treatment-related sexual dysfunction under psychopharmacological agents. In this article, we introduce common neurobiological concepts regarding cerebral sexual responses based on neuroimaging findings and we discuss challenges and findings regarding investigating the neuromodulation of neural sexual stimulus processing. In particular, we summarize findings from our research program investigating how neural correlates of sexual stimulus processing are modulated by serotonergic, dopaminergic, and noradrenergic antidepressant medication in healthy males.
    Keywords noradrenaline ; dopamine ; erotic stimulus ; fMRI ; healthy ; human ; serotonin ; processing
    Language English
    Document type Article
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  3. Article: Alterations in Brain Structure and Amplitude of Low-frequency after 8 weeks of Mindfulness Meditation Training in Meditation-Naïve Subjects

    Walter, Martin

    Scientific reports, 9(1):10977

    2019  

    Abstract: Increasing neuroimaging evidence suggests that mindfulness meditation expertise is related to different functional and structural configurations of the default mode network (DMN), the salience network (SN) and the executive network at rest. However, ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract Increasing neuroimaging evidence suggests that mindfulness meditation expertise is related to different functional and structural configurations of the default mode network (DMN), the salience network (SN) and the executive network at rest. However, longitudinal studies observing resting network plasticity effects in brains of novices who started to practice meditation are scarce and generally related to one dimension, such as structural or functional effects. The purpose of this study was to investigate structural and functional brain network changes (e.g. DMN) after 40 days of mindfulness meditation training in novices and set these in the context of potentially altered depression symptomatology and anxiety. We found overlapping structural and functional effects in precuneus, a posterior DMN region, where cortical thickness increased and low-frequency amplitudes (ALFF) decreased, while decreased ALFF in left precuneus/posterior cingulate cortex correlates with the reduction of (CES-D) depression scores. In conclusion, regional overlapping of structural and functional changes in precuneus may capture different components of the complex changes of mindfulness meditation training.
    Keywords Neural circuits ; Translational research
    Language English
    Document type Article
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  4. Article: Role of inflammation in depression relapse

    Walter, Martin

    Journal of neuroinflammation, 16:90

    2019  

    Abstract: Major depressive disorder (MDD) is a leading cause of disability worldwide. After the first episode, patients with remitted MDD have a 60% chance of experiencing a second episode. Consideration of therapy continuation should be viewed in terms of the ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract Major depressive disorder (MDD) is a leading cause of disability worldwide. After the first episode, patients with remitted MDD have a 60% chance of experiencing a second episode. Consideration of therapy continuation should be viewed in terms of the balance between the adverse effects of medication and the need to prevent a possible relapse. Relapse during the early stages of MDD could be prevented more efficiently by conducting individual risk assessments and providing justification for continuing therapy. Our previous work established the neuroimaging markers of relapse by comparing patients with recurrent major depressive disorder (rMDD) in depressive and remitted states. However, it is not known which of these markers are trait markers that present before initial relapse and, consequently, predict disease course. Here, we first describe how inflammation can be translated to subtype-specific clinical features and suggest how this could be used to facilitate clinical diagnosis and treatment. Next, we address the central and peripheral functional state of the immune system in patients with MDD. In addition, we emphasize the important link between the number of depressive episodes and rMDD and use neuroimaging to propose a model for the latter. Last, we address how inflammation can affect brain circuits, providing a possible mechanism for rMDD. Our review suggests a link between inflammatory processes and brain region/circuits in rMDD.
    Keywords Functional magnetic resonance imaging ; (Neuro) inflammation ; Recurrent major depressive disorder ; Vagus nerve stimulation
    Language English
    Document type Article
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  5. Article: Interaction of Sex and Age on the Dissociative Effects of Ketamine Action in Young Healthy Participants

    Walter, Martin

    Frontiers in neuroscience, 13:616

    2019  

    Abstract: Ketamine is a drug that reduces depressive and elicits schizophrenia-like symptoms in humans. However, it is largely unexplored whether women and men differ with respect to ketamine-action and whether age contributes to drug-effects. In this study we ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract Ketamine is a drug that reduces depressive and elicits schizophrenia-like symptoms in humans. However, it is largely unexplored whether women and men differ with respect to ketamine-action and whether age contributes to drug-effects. In this study we assessed dissociative symptoms via the Clinician Administered Dissociative States Scale (CADSS) in a total of 69 healthy subjects aged between 18 and 30 years (early adulthood) after ketamine or placebo infusion. Dissociative symptoms were generally increased only in the ketamine group post-infusion. Specifically, within the ketamine group, men reported significantly more depersonalization and amnestic symptoms than women. Furthermore, with rising age only men were less affected overall with respect to dissociative symptoms. This suggests a sex-specific protective effect of higher age which may be due to delayed brain maturation in men compared to women. We conclude that it is crucial to include sex and age in studies of drug effects in general and of ketamine-action in specific to tailor more efficient psychiatric treatments.
    Keywords depersonalization ; age ; brain maturation ; dissociation ; ketamine ; sex
    Language English
    Document type Article
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  6. Article: Expectation of sexual images of adults and children elicits differential dorsal anterior cingulate cortex activation in pedophilic sexual offenders and healthy controls

    Walter, Martin

    NeuroImage: Clinical, 23:101863

    2019  

    Abstract: BACKGROUND: Pedophilic disorder is characterized by increased sexual interest towards children, with comparatively lesser interest towards adults. In real life, the behavior of subjects with pedophilic disorder is shaped by evaluative processes in ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract BACKGROUND: Pedophilic disorder is characterized by increased sexual interest towards children, with comparatively lesser interest towards adults. In real life, the behavior of subjects with pedophilic disorder is shaped by evaluative processes in response to sexually relevant cues. Therefore, brain activation during anticipation of sexually relevant cues is of potential interest. Whereas previous research demonstrated reduced activation when viewing adult (non-preferred)sexual stimuli in pedophilic sex offenders (PSOs), it is not known if anticipation of preferred versus unpreferred stimuli will elicit differential brain activation. METHODS: Two fMRI studies (1.5 and 7 Tesla)were conducted in separate samples, each with 26 subjects (13/13 PSOs/controls)to assess brain activity during expectancy of subsequent adult (non-preferred)sexual stimuli. In the second study (7 Tesla)additionally child (preferred)cues were presented. RESULTS: As predicted, expectancy of adult sexual stimuli generated smaller dorsal anterior cingulate cortex (dACC)activation in PSOs in both studies, driven by stronger activation during expectancy of adult erotic stimuli in non-pedophilic controls (HCs). In the second study, PSOs showed significantly increased activations in dACC during expectancy of child stimuli compared with expectancy of adult stimuli. This difference was significantly greater compared to the same contrast in HCs, thus demonstrating preference specificity of dACC activation. CONCLUSION: Our findings support the notion of decreased brain activation to adult cues in PSOs and preference specificity in neural response during expectancy of erotic stimuli. The localization of these cue reactivity differences in the salience network supports the interpretation that PSOs show abnormally increased preparatory activation even before relevant sexual stimuli are actually presented.
    Keywords Dorsal anterior cingulate cortex (dACC) ; Expectancy ; Sexual processing ; Pedophilic disorder ; Pedophilic sex offenders ; fMRI
    Language English
    Document type Article
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  7. Article: Non-invasive stimulation of vagal afferents reduces gastric frequency

    Walter, Martin

    Brain stimulation, 13(2):470-473

    2019  

    Abstract: Metabolic feedback between the gut and the brain relayed via the vagus nerve contributes to energy homeostasis. We investigated in healthy adults whether non-invasive stimulation of vagal afferents impacts energy homeostasis via efferent effects on ... ...

    Institution Leibniz-Institut für Neurobiologie
    Abstract Metabolic feedback between the gut and the brain relayed via the vagus nerve contributes to energy homeostasis. We investigated in healthy adults whether non-invasive stimulation of vagal afferents impacts energy homeostasis via efferent effects on metabolism or digestion. In a randomized crossover design, we applied transcutaneous auricular vagus nerve stimulation (taVNS) while recording efferent metabolic effects using simultaneous electrogastrography (EGG) and indirect calorimetry. We found that taVNS reduced gastric myoelectric frequency (p = .008), but did not alter resting energy expenditure. We conclude that stimulating vagal afferents induces gastric slowing via vagal efferents without acutely affecting net energy expenditure at rest. Collectively, this highlights the potential of taVNS to modulate digestion by activating the dorsal vagal complex. Thus, taVNS-induced changes in gastric frequency are an important peripheral marker of brain stimulation effects.
    Keywords Resting energy expenditure ; Energy homeostasis ; Electrogastrogram ; Transcutaneous auricular vagus nerve stimulation ; taVNS
    Language English
    Document type Article
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  8. Book ; Online: Recent Advances on the Multimodal Search for Markers of Treatment Response in Affective Disorders: From Bench to Bedside?

    M Schmidt, Frank / Sander, Christian / Walter, Martin

    2019  

    Keywords Medicine ; Psychiatry ; Depression ; bipolar disorder ; Editorial ; Neuroinflammation ; therapy prediction
    Size 1 electronic resource (144 pages)
    Publisher Frontiers Media SA
    Document type Book ; Online
    Note English ; Open Access
    HBZ-ID HT021231245
    ISBN 9782889632305 ; 288963230X
    Database ZB MED Catalogue: Medicine, Health, Nutrition, Environment, Agriculture

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  9. Book ; Audio / Video ; Thesis: Untersuchung spezifischer Hirnprozesse sexueller Verarbeitung der Gesunden und pädophilen Patienten anhand funktioneller Kernspintomographie

    Walter, Martin

    2008  

    Language German
    Size 1 CD-ROM, 12 cm
    Publishing country Germany
    Document type Book ; Audio / Video ; Thesis
    Thesis / German Habilitation thesis Magdeburg, Univ., Diss., 2008
    HBZ-ID HT015628739
    Database Catalogue ZB MED Medicine, Health

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    In stock of ZB MED Cologne/Königswinter

    Shelf markLoan statusLocation
    2007 MO 1199 order for loan Magazin

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  10. Article ; Online: Rolling Contact Fatigue and White Etching Cracks of Bearings

    Walter Martin Holweger / Jürgen Gegner

    Lubricants, Vol 11, Iss 247, p

    2023  Volume 247

    Abstract: Lubricants have taken a leading role as drive- train system components in recent years, mainly attributed to their viscosity as a quality criterion [.] ...

    Abstract Lubricants have taken a leading role as drive- train system components in recent years, mainly attributed to their viscosity as a quality criterion [.]
    Keywords n/a ; Science ; Q
    Language English
    Publishing date 2023-06-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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