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Biomedical subjects

Dennis J L G Schutter

Publications and source records attributed to Dennis J L G Schutter.

At least 19 recordsLinked to original sources
PubMed2006

An electrophysiological link between the cerebellum, cognition and emotion: frontal theta EEG activity to single-pulse cerebellar TMS.

Early intracranial electrical stimulation studies in animals demonstrated cerebellar connectivity to brain structures involved in cognitive and emotive functions. Human electrophysiological data to support cerebellum involvement in the latter functions are however lacking. In the present study, electrophysiological responses were recorded to single-pulse transcranial magnetic stimulation (TMS) over the vermis in healthy human volunteers. Increased theta activity was observed after single-pulse vermis TMS as compared to sham and occipital TMS. Both animal and human research relate theta activity with the septo-hippocampal complex, an important brain structure involved in cognition and emotion. The present electrophysiological study supports the earlier intracranial electrical stimulation findings by demonstrating cerebellar involvement in the modulation of the core frequencies related to cognitive and emotive aspects of human behavior.

Adult↗
PubMed2006

Anxious apprehension increases coupling of delta and beta oscillations.

Recent findings showing that anxiety is associated with enhanced coupling of EEG rhythms imply higher information exchange between populations of neurons associated with different oscillatory systems. In this study, influence of uncertainty on alpha-delta anticorrelation and delta-beta coupling was studied in 39 subjects (27 females) aged 19 to 30 years who also filled out the State Trait Anxiety Inventory. A measure of alpha-delta anticorrelation showed trait-like properties being uniformly higher in high trait anxiety subjects independent of experimental manipulation. Contrariwise, delta-beta coupling appeared only in anxiogenic situation both in high and low anxiety subjects.

Adult↗
PubMed2006

A case of illusory own-body perceptions after transcranial magnetic stimulation of the cerebellum.

Illusory own-body perceptions are 'body in space' misinterpretations of the brain and belong to the class of out-of-body experiences wherein the angular gyrus seems importantly implicated. In the present study additional cerebellum involvement in illusory own-body perceptions was investigated in a healthy young female right-handed volunteer. Transcranial magnetic stimulation (TMS) was applied over the cerebellum. Placebo cerebellum TMS and occipital TMS served as control conditions. Illusory own-body perceptions accompanied by electric brain activity over the somatosensory cortex were only observed after cerebellum TMS. The data provide the first evidence that the cerebellum might be involved in a neuronal network underlying illusory own-body perceptions.

Adult↗
PubMed2006

A standardized motor threshold estimation procedure for transcranial magnetic stimulation research.

OBJECTIVES: To introduce and to test a simple standardized motor threshold (MT) estimation procedure for transcranial magnetic stimulation (TMS) research. METHODS: A 5-step MT estimation procedure was introduced, and interestimator reliability was tested by comparing MTs as determined by an experienced and a trainee TMS researcher in a double-blind design. RESULTS: The parametric Pearson correlation between the MTs of the experienced and the MTs of the trainee TMS researcher was 0.95 (P < 0.001). CONCLUSIONS: The currently proposed estimation procedure may be helpful in obtaining reliable MT values in experimental and clinical settings.

Algorithms↗
PubMed2006

Increased positive emotional memory after repetitive transcranial magnetic stimulation over the orbitofrontal cortex.

OBJECTIVE: Several studies have demonstrated increased left orbitofrontal cortex (OFC) activity during negative and depressed mood. These mood states have also been associated with reduced memory for positive emotional stimuli. The aim of the present study was to investigate whether slow, inhibitory repetitive transcranial magnetic stimulation (rTMS) over the left OFC would improve memory for positive material. METHODS: We carried out a study with a double-blind, within-subjects design, in which 12 healthy volunteers received 20 minutes of slow rTMS over the left OFC, placebo treatment over the left OFC and rTMS over the left dorsolateral portion of the prefrontal cortex. Effects on memory for fearful and happy faces were investigated. RESULTS: Memory for happy faces was significantly improved after rTMS over the left OFC compared with placebo (t10 = 2.4, p = 0.037). CONCLUSIONS: These findings suggest a role of the OFC in positive emotional memory, which is in accordance with neuroimaging and neuropsychological data. It may be argued that dense projections from the OFC to the limbic emotional circuit are involved in emotional memory and, therefore, play a role in the effects of rTMS that we observed.

Adolescent↗
PubMed2005

Electrophysiological correlates of cortico-subcortical interaction: a cross-frequency spectral EEG analysis.

OBJECTIVE: Several studies have provided evidence for the notion that the coupling between slow and fast frequency in the EEG spectrum indicates cortico-subcortical cross-talk (CSC-ct). In addition, findings for increased limbic activation due to reduced cortical inhibition have recently been acquired. To get further insights into these mechanisms, the current study investigated whether CSC-ct would decrease as a function of increased slow (SW) or fast wave (FW) activity. METHODS: Resting state EEG recordings were obtained from 46 healthy, right-handed participants. CSC-ct was quantified by computing cross-frequency correlations between the power in the slow and fast frequency range. CSC-ct was compared between groups with relatively low and high SW activity and groups with relatively low and high FW activity. RESULTS: Relatively reduced SW, but not FW activity was associated with a significant coupling between slow and fast frequency EEG. Furthermore, relatively enhanced resting state SW activity was paralleled by slow and fast frequency EEG decoupling. CONCLUSIONS: These findings are in line with the notion that increased subcortical drive can go accompanied by reduced CSC-ct. SIGNIFICANCE: Cross-frequency EEG analyses might provide a unique approach to obtain novel insights into cortico-subcortical interactions in relation to affective and cognitive behavior.

Adolescent↗
PubMed2005

Testosterone reduces unconscious fear but not consciously experienced anxiety: implications for the disorders of fear and anxiety.

BACKGROUND: The fear-reducing properties of testosterone have been firmly established in animals but not in humans. However, human data on the relation between testosterone, fear, and anxiety have predominantly involved questionnaires that index cortically executed conscious appraisal of anxious mood. Animal studies, on the other hand, indicate that the effects of testosterone on motivation and emotion are of subcortical origin and of unconscious nature. Presently, it was hypothesized that a single testosterone administration to humans would reduce unconscious fear but not consciously experienced anxiety. METHODS: In a placebo-controlled, double-blind crossover design, a single dose of testosterone (.5 mg) or placebo was administered to 16 healthy female volunteers. Afterward, a masked emotional Stroop task measured unconscious emotional responses to fearful faces, while multiple self-reports of mood indexed consciously experienced anxiety. RESULTS: As hypothesized, the habitual vigilant emotional response to the masked fearful face observed in the placebo condition was significantly reduced after testosterone was administered, while the self-reported measures of anxiety remained unaffected. CONCLUSIONS: These data provide the first direct evidence for fear-reducing properties of testosterone in humans. Furthermore, by dissociating specific aspects of fear and anxiety in humans, this outcome highlights that testosterone's effects on motivation and emotion concern the subcortical affective pathways of the brain.

Adult↗
PubMed2005

Electrophysiological ratio markers for the balance between reward and punishment.

It has been argued that prototypical forms of psychopathology result from an imbalance in reward and punishment systems. Recent studies suggest that the ratios between slower and faster waves of the electroencephalogram (EEG) index this motivational balance and might therefore have diagnostic value for psychopathology. To scrutinize this notion, the present study investigated whether resting state EEG ratios would predict decision making on the Iowa gambling task (Iowa-GT), a well-known marker for motivational imbalance. A resting state EEG recording was acquired followed by the Iowa-GT in twenty-eight healthy right-handed volunteers. Results showed that higher versus lower EEG ratios were associated with disadvantageous versus advantageous decision making strategies indicating motivational imbalances in reward- and punishment-driven behavior, respectively. This finding provides the first direct evidence that the electrophysiologically derived EEG ratios can serve as biological markers for balance and imbalance in motivation.

Adult↗
PubMed2005

The cerebellum on the rise in human emotion.

For decennia the cerebellum has largely been excluded from scientific enquiry beyond motor function. However, the intimate afferent and efferent connections to the midbrain and limbic system provide for the neuroanatomical foundation of cerebellar involvement in emotion and emotional disorders. Moreover, an increasing body of empirical evidence indicates that the cerebellum may be involved in emotion regulation. Both functional and structural abnormalities of the cerebellum have been demonstrated in emotional disorders, including depression and schizophrenia. Research shows that the functional repertoire of the cerebellum is broader than previously thought and its involvement in emotion is noteworthy.

Adult↗
PubMed2005

Administration of testosterone increases functional connectivity in a cortico-cortical depression circuit.

Increasing evidence suggests that the steroid hormone testosterone (T) enhances libido and decreases depression. Even a single administration of T (0.5 mg sublingually) in healthy young women is sufficient to enhance physiological sexual responsiveness. Such physiological evidence is not yet available for the link between T and depression. Recent research has revealed that lowered functional connectivity in a specific cortico-cortical pathway may be a sensitive physiological index for depression. This pathway, comprised of the left prefrontal and right parietal cortex, has been named a cortical depression circuit. In the present study, a single dose of T was administered to healthy young women to investigate the effects on the functional connectivity in this cortico-cortical depression circuit. It was hypothesized that administration of T would lead to an increase of functional connectivity. In a double-blind placebo-controlled, crossover design, fourteen healthy females received (sublingually) a single dose of 0.5 mg T or placebo in a randomly assigned fashion. Three hours after drug administration the functional coupling between the left prefrontal and right parietal cortex was established by measuring the interhemispheric electroencephalogram (EEG) coherence for the different frequency bands. Compared to placebo, T administration significantly increased the functional connectivity in the sigma (1-3 Hz) frequency range between the left prefrontal and right parietal cortex. Reductions in interhemispheric coherence in the sigma frequency range have been observed in clinically depressed patients. Thus the present findings may provide a first insight into the neurobiological mechanism by which T decreases depression. The fact that only a single dose of T was able to induce the effect in healthy female subjects suggests that the mechanism is highly sensitive. A feasible application of T treatment in the struggle against depression is discussed.

Adult↗
PubMed2005

A framework for targeting alternative brain regions with repetitive transcranial magnetic stimulation in the treatment of depression.

It has been argued that clinical depression is accompanied by reductions in cortical excitability of the left prefrontal cortex (PFC). In support of this, repetitive transcranial magnetic stimulation (rTMS), which is a method of enhancing cortical excitability, has shown antidepressant efficacy when applied over the left PFC, although the overall therapeutic effects remain inconclusive. The cerebral pathophysiology of depression is, however, not limited to dysfunctions in the PFC, thus, targeting alternative brain regions with rTMS may provide new therapeutic windows in the treatment of depression. Evidence from electroencephalography and lesion studies suggests that not only is the left PFC involved in depression but also the parietal cortex and cerebellum. Furthermore, rTMS over the parietal cortex and the cerebellum has been found to improve mood and emotional functioning, at least in healthy volunteers. We have integrated these findings in an rTMS-oriented theoretical framework for the neurobiology of low mood and depression. To establish the possible therapeutic efficacy of this model, whereby, for example, the application of slow rTMS over the right parietal cortex and fast rTMS over the cerebellum may be beneficial in different subtypes of depression, clinical rTMS studies that target the parietal cortex and cerebellum are warranted.

Brain↗
PubMed2004

Extending the global workspace theory to emotion: phenomenality without access.

Recent accounts on the global workspace theory suggest that consciousness involves transient formations of functional connections in thalamo-cortico-cortical networks. The level of connectivity in these networks is argued to determine the state of consciousness. Emotions are suggested to play a role in shaping consciousness, but their involvement in the global workspace theory remains elusive. In the present study, the role of emotion in the neural workspace theory of consciousness was scrutinized by investigating, whether unconscious (masked) and conscious (unmasked) display of emotional compared to neutral facial expressions would differentially modulate EEG coherence. EEG coherence was measured by means of computing an average EEG coherence value between the frontal, parietal, and midline scalp sites. Objective awareness checks evidenced that conscious identification of the masked facial expressions was precluded. Analyses revealed reductions in EEG coherence in the lower frequency range for the masked as compared to unmasked neutral facial expressions. Crucially, a decline in EEG coherence was not observed for the emotional facial expressions. In other words, the level of EEG coherence did apparently vary as a function of awareness, but not when emotion was involved. The current finding suggests that EEG coherence is modulated by unconscious emotional processes, which extends common views on the global workspace architecture of consciousness.

Adult↗
PubMed2004

Functionally dissociated aspects in anterior and posterior electrocortical processing of facial threat.

The angry facial expression is an important socially threatening stimulus argued to have evolved to regulate social hierarchies. In the present study, event-related potentials (ERP) were used to investigate the involvement and temporal dynamics of the frontal and parietal regions in the processing of angry facial expressions. Angry, happy and neutral faces were shown to eighteen healthy right-handed volunteers in a passive viewing task. Stimulus-locked ERPs were recorded from the frontal and parietal scalp sites. The P200, N300 and early contingent negativity variation (eCNV) components of the electric brain potentials were investigated. Analyses revealed statistical significant reductions in P200 amplitudes for the angry facial expression on both frontal and parietal electrode sites. Furthermore, apart from being strongly associated with the anterior P200, the N300 showed to be more negative for the angry facial expression in the anterior regions also. Finally, the eCNV was more pronounced over the parietal sites for the angry facial expressions. The present study demonstrated specific electrocortical correlates underlying the processing of angry facial expressions in the anterior and posterior brain sectors. The P200 is argued to indicate valence tagging by a fast and early detection mechanism. The lowered N300 with an anterior distribution for the angry facial expressions indicates more elaborate evaluation of stimulus relevance. The fact that the P200 and the N300 are highly correlated suggests that they reflect different stages of the same anterior evaluation mechanism. The more pronounced posterior eCNV suggests sustained attention to socially threatening information.

Adult↗