Individual differences in the effects of salience and reward on impulse control and action selection

Impulse control and adequate decision making are vital functions when it comes to detection and adherence to personal goals and societal rules. In the current study we tested the hypothesis that increasing the salience of environmental cues would be most effective in improving impulse control, as assessed by a stop-signal task, in subjects with low environmental susceptibility as indexed by low pre-stimulus EEG alpha power. In addition, we anticipated that an external-reward manipulation improves performance during a Go/No go task, especially in individuals with low task-induced motivation as indexed by low theta/beta power ratios. High salience of stop signals enhanced stopping performance but there was no difference in responsivity to the salience manipulation between participants with high and low EEG alpha power. Individuals with low theta/beta power ratios responded more accurately when rewards were involved. Together these results suggest that increasing the salience of external cues may help impulse control in general, whereas the effectiveness of external-reward manipulations is higher in individuals with low task-induced motivation.

Lower cerebello-cortical functional connectivity in veterans with reactive aggression symptoms: A pilot study

A significant number of veterans experience irritability and aggression symptoms as a result of being exposed to extremely stressful and life-threatening situations. In addition to the well-established involvement of the brain's cortico-subcortical circuit in aggression-related behaviours, a role of the deep cerebellar nuclei (DCN) in reactive aggression has been suggested. In the present study, seed-based resting-state functional connectivity between the DCN and cortico-subcortical areas was explored in veterans with and without reactive aggression symptoms. Nineteen male veterans with reactive aggression symptoms and twenty-two control veterans without reactive aggression symptoms underwent 3T resting-state functional MRI scans. Region-of-interest (ROI) analyses that included the amygdala, hypothalamus and periaqueductal grey as ROIs did not yield significant group-related differences in resting-state functional connectivity with the DCN. However, exploratory whole-brain analysis showed that veterans with reactive aggression symptoms exhibited lower functional connectivity between the DCN and the orbitofrontal cortex compared to control veterans. Our findings provide preliminary evidence for the possible involvement of a cerebello-prefrontal pathway in reactive aggression in male veterans.

[Electroencephalography and connectivity in delirium]

BACKGROUND

Delirium is associated with neurophysiological changes that can be identified with quantitative EEG analysis techniques (qEEG).

AIM

To provide an overview of studies on neurophysiological changes in delirium using various qEEG analysis techniques.

METHOD

Literature review.

RESULTS

In delirium, there is an increase in delta and theta activity but a decrease in activity in the alpha frequency band. Additionally, there is a decrease in functional connectivity and efficiency of the brain network in the alpha frequency band.

CONCLUSION

Delirium is characterized by diffuse slowing of the EEG, reduced functional connectivity, and decreased efficiency of the brain network. Improved functional connectivity could be a new approach to treat delirium.

[Neural networks and clinical efficacy of transcranial brain stimulation in psychiatry]

BACKGROUND

Non-invasive forms of brain stimulation, including transcranial magnetic stimulation and direct current stimulation, are increasingly being considered by clinicians as a somatic treatment option for psychiatric disorders.

AIM

Review article on the history, efficacy transcranial brain stimulation in psychiatric disorders and the role of neural networks for improving clinical efficacy.

METHOD

Review of scientific literature.

RESULTS

Transcranial magnetic stimulation has been proven effective for the treatment of depression, but treatment efficacy varies widely for other psychiatric disorders. Transcranial direct current stimulation is still at an experimental stage, but results suggest that using weak currents can have positive effects. Neuroscience research provides tools for improving therapeutic outcomes based on neural network approaches.

CONCLUSION

Transcranial brain stimulation grafted on network information appears to be a promising approach for enhancing therapeutic outcome in psychiatric disorders.

NMDA Receptor-Mediated Motor Cortex Plasticity After 20 Hz Transcranial Alternating Current Stimulation

Transcranial alternating current stimulation (tACS) has been shown to modulate neural oscillations and excitability levels in the primary motor cortex (M1). These effects can last for more than an hour and an involvement of N-methyl-d-aspartate receptor (NMDAR) mediated synaptic plasticity has been suggested. However, to date the cortical mechanisms underlying tACS after-effects have not been explored. Here, we applied 20 Hz beta tACS to M1 while participants received either the NMDAR antagonist dextromethorphan or a placebo and the effects on cortical beta oscillations and excitability were explored. When a placebo medication was administered, beta tACS was found to increase cortical excitability and beta oscillations for at least 60 min, whereas when dextromethorphan was administered, these effects were completely abolished. These results provide the first direct evidence that tACS can induce NMDAR-mediated plasticity in the motor cortex, which contributes to our understanding of tACS-induced influences on human motor cortex physiology.

A randomized controlled trial of a standard 4-week protocol of repetitive transcranial magnetic stimulation in severe treatment resistant depression

BACKGROUND

Treatment options for major depressive disorder (MDD) in individuals who are depressed for at least 2 years and failed two or more different types of therapeutic intervention, remain scarce. Being less invasive than electroconvulsive therapy, repetitive transcranial magnetic stimulation (rTMS) might be an alternative treatment option.

RESEARCH QUESTION

Does high frequency rTMS applied over the left prefrontal cortex ameliorate depressive symptoms in patients with treatment resistant major depressive disorder and is the efficacy dependent on treatment resistance?

METHOD

We performed a randomized controlled trial investigating the effect of twenty sessions of real or sham-rTMS, during 4 consecutive weeks. Efficacy was blindly rated with the Hamilton depression rating scale (HDRS-17) at baseline and 1 week after end of treatment, and the Dutch method for quantification of treatment resistance in Depression (DM-TRD) was assessed at baseline.

RESULTS

An interim analysis showed no differences in antidepressant response between real and sham rTMS and we therefore discontinued the RCT after 31 patients. The mean difference of the HDRS score between baseline and post-treatment was 3.7 (± 4.0; change 16%), indicating a small but significant improvement across time (F(1,30)=25.4;p < 0.01). There were no differences however between the treatment arms (F(1.30) = 1.5;p = 0.23). We did find a negative correlation between the change in HDRS score and DM-TRD in the active rTMS group, but this correlation was not significantly different from the sham group.

CONCLUSION

"Standard" 4-week rTMS treatment is not effective in chronic, severe treatment-resistant depressed patients. While a replication of our data in this patient group may be ethically difficult, further research with less treatment resistant patients might help in positioning rTMS within the current stepped care approach to depression.

[Non-invasive brain stimulation for the treatment of depression]

Depression is one of the most common psychiatric disorders and is a heavy burden, not only for the patient and his or her environment but also in economic and social terms. 35% of depressed patients do not recover after standard treatment with medication or psychotherapy. There is a need for more effective treatment options for depression. In recent decades, new forms of brain stimulation have been developed for the treatment of depression, the most important of which is transcranial magnetic stimulation (TMS). TMS uses magnetic pulses to influence brain activity. Meta-analyses show approximately 30-40% of patients respond to treatment with repetitive TMS. The depression goes into remission in about 20-30% of cases. Research has led to new treatment protocols and variations on the conventional TMS method. More research into the effectiveness of these developments is needed. We recommend using TMS as an add-on treatment more often when the patient has completed two steps of the treatment guideline.

[Consensus statement on the application of rTMS in depression in the Netherlands and Belgium]

Since 2017, repetitive transcranial magnetic stimulation (rTMS) has become eligible for reimbursement for the treatment of therapy-resistant depression in the Dutch healthcare system.<br/> AIM: To initiate a guideline in the Netherlands and Belgium for the safe and effective application of rTMS for the treatment of depression.<br/> METHOD: Based on literature review, existing guidelines and consensus among Dutch rTMS experts, recommendations were developed regarding the implementation of rTMS as a treatment of depression. All available evidence was weighed and discussed among all co-authors and recommendations were reached by consensus among the group.<br/> RESULTS: rTMS targeting the dorsolateral prefrontal cortex (DLPFC) should be seen as a first choice in the treatment of depression using high-frequency rTMS (left) or, as an alternative, low-frequency rTMS (right). Stimulation protocols should use more than 1000 pulses per session for an average of 20-30 sessions, offered in 2-5 sessions per week. Contraindications for rTMS include epilepsy, intracranial presence of (magnetisable) metals, pacemaker and cochlear implant.<br/> CONCLUSION: rTMS, performed by competent professionals is an effective and safe treatment for depression.

[rTMS for treatment resistant depression - proposal for a treatment protocol]

At present, the use of repetitive transcranial magnetic stimulation (rtms) for treatment-resistant depression is sufficiently substantiated to be applied in clinical practice. In the Netherlands, it will be reimbursed when offered in combination with cognitive behavior therapy.<br/> AIM: Proposal for a clinical treatment protocol for rtms in The Netherlands.<br/> METHOD: A study of the literature and a critical appraisal of available international guidelines for rtms.<br/> RESULTS: rtms is a safe treatment for patients suffering from a moderate to severe depressive disorder that is relatively treatment-resistant. The duration of the effect is still unknown. It is advised to stimulate the left dorsolateral prefrontal cortex using an intensity of 120% of the resting motor threshold, with a frequency of 10 Hz and using 3000 pulses per session during a total of 20-30 sessions.<br/> CONCLUSION: The proposed treatment protocol is favored based on the available evidence when rtms is used as a treatment aimed to acutely decrease the severity of depressive symptoms. It is further proposed to systematically collect technical and outcome data on treatment with rtms to further improve treatment with rtms in clinical practice.

Alpha-band transcranial alternating current stimulation modulates precision, but not gain during whole-body spatial updating

Spatial updating is essential to maintain an accurate representation of our visual environment when we move. A neural mechanism that contributes to this ability is called remapping: the transfer of visual information from neural populations that code a location before the motion to those that encode it after the motion. While there is ample evidence for neural remapping in conjunction with eye movements, only recent findings suggest a role of this mechanism for whole-body motion updating, based on the observation that alpha band (10Hz) activity is selectively reorganized during remapping. This study tested whether alpha oscillations directly contribute to whole-body motion updating using transcranial alternating current stimulation (tACS). In a double blind sham controlled design, healthy volunteers received 10Hz tACS at an intensity of 1mA over either the left or right posterior hemisphere during a whole-body motion updating task. Updating performance was assessed psychometrically and indices of gain and precision were obtained. No tACS-related effects on updating gain were found, irrespective of whether the remapping was across or within the hemispheres. In contrast, updating precision was enhanced when a target representation had to be internally remapped to the stimulated hemisphere, but not in other remapping conditions. Our observations suggest that alpha band oscillations do not directly affect the transfer of target representations during remapping, but increase the fidelity of the updated representation by attenuating interference of afferent information.

[Minimally invasive brain stimulation for unipolar depression]

BACKGROUND

Unipolar depression is one of the most prevalent psychiatric disorders and has a high impact at individual and societal level. Commonly used treatments such as antidepressants and psychotherapy are often not effective.

AIM

To determine the efficacy of repetitive transcranial magnetic stimulation (rTMS) and direct current stimulation (tDCS) as minimally invasive forms of treatment for unipolar depression.

METHOD

We searched the literature.

RESULTS

rTMS is effective in treating unipolar depression and is comparable to existing forms of medication and behavioural therapy. The effects of tDCS are promising, but more research is needed.

CONCLUSION

rTMS is a useful addition to the existing arsenal of treatment for unipolar depression.

[Ethical considerations regarding the use of transcranial magnetic stimulation in the treatment of depression]

BACKGROUND

Transcranial magnetic stimulation (TMS) has proved effective in the treatment of depression. However, the step that was needed to progress from positive research results to the actual use of TMS to treat patients has raised a number of ethical concerns. The concerns extend beyond matters such as the safety of the technique, the patient's right of access to therapy and the patient's informed consent; ethics are involved because the new treatment can be mind-bending and can interfere with the patient's autonomy and decision-making capacity.

AIM

To discuss ethical issues raised by the use of TMS in the treatment of depression.

METHOD

We reviewed the relevant scientific literature.

RESULTS

The effects of the treatment on the patient's genuine wishes and on his or her views on the efficacy of the treatment are technique-related ethical issues that have not yet been adequately addressed. Furthermore, the effects of TMS on the patient's autonomy and mental capacity and the 'last resort' argument in relation to the effectiveness of the therapy are context-related considerations that warrant further discussion.

CONCLUSION

There will have to be more research and discussion among researchers and clinicians about specific ethical questions before TMS can take its rightful place in clinical practice.

Empathy and prosocial behavior in response to sadness and distress in 6- to 7-year olds diagnosed with disruptive behavior disorder and attention-deficit hyperactivity disorder

Empathy has been associated with decreased antisocial and increased prosocial behavior. This study examined empathy and prosocial behavior in response to sadness and distress in disruptive behavior disorder (DBD) and attention-deficit hyperactivity disorder (ADHD). Six- and 7-year-old children with DBD (with and without ADHD) (n = 67) and with ADHD only (n = 27) were compared to typically developing children (TD) (n = 37). Parents and teachers rated affective empathy in response to sadness and distress on the Griffith Empathy Measure. Children reported affective empathic ability in response to sad story vignettes. Empathy-induced prosocial behavior in response to sadness and distress was assessed with a computer task, the Interpersonal Response Task (IRT). Compared to TD, children with DBD (with and without ADHD) and those with ADHD only were rated as less empathic by their teachers, but not by their parents. No differences between groups were observed in children who reported affect correspondence. Children with DBD (with and without ADHD) showed less prosocial behavior in response to sadness and distress compared to TD. Children with ADHD only did not differ from TD. An additional analysis comparing all children with a diagnosis to the TD group revealed that the difference in prosocial behavior remained after controlling for ADHD symptoms, but not after controlling for DBD symptoms. These findings of impaired empathy-induced prosocial behavior in response to sadness and distress in young children with DBD suggest that interventions to ameliorate peer relationships may benefit from targeting on increasing prosocial behavior in these children.

Electromyographic responses to emotional facial expressions in 6-7year olds: a feasibility study

Preliminary studies have demonstrated that school-aged children (average age 9-10years) show mimicry responses to happy and angry facial expressions. The aim of the present study was to assess the feasibility of using facial electromyography (EMG) as a method to study facial mimicry responses in younger children aged 6-7years to emotional facial expressions of other children. Facial EMG activity to the presentation of dynamic emotional faces was recorded from the corrugator, zygomaticus, frontalis and depressor muscle in sixty-one healthy participants aged 6-7years. Results showed that the presentation of angry faces was associated with corrugator activation and zygomaticus relaxation, happy faces with an increase in zygomaticus and a decrease in corrugator activation, fearful faces with frontalis activation, and sad faces with a combination of corrugator and frontalis activation. This study demonstrates the feasibility of measuring facial EMG response to emotional facial expressions in 6-7year old children.

[Transcranial magnetic stimulation as a treatment for depression]

BACKGROUND

The high incidence of depressive disorder in the Netherlands calls for additional forms of therapy. Transcranial magnetic stimulation (TMS) is a form of non-invasive brain stimulation that has been investigated in the last 15 years in order to find out whether this form of stimulation is effective in the treatment of depression.

AIM

To discover whether TMS has proved effective in the treatment of depressed patients.

RESULTS

Results show that tms treatment is safe when applied to the frontal lobes of the cerebral cortex and that the therapeutic effect is comparable to the effect of psychotherapy and antidepressants. Future studies should concentrate on an increase in efficiency by providing more insight into the working mechanisms and the effect of individual differences. Follow-up studies are needed to investigate the duration of the antidepressive effect.

CONCLUSION

TMS seems to be a promising tool for the treatment of depressive disorders. However, there are many questions and uncertainties about the efficiency and applicability of TMS.

Quantitative review of the efficacy of slow-frequency magnetic brain stimulation in major depressive disorder

BACKGROUND

Slow-frequency repetitive transcranial magnetic stimulation (rTMS) to the frontal cortex has been suggested as a safer and better tolerable alternative to fast-frequency rTMS in the treatment of major depressive disorder (MDD). The aim of the present study was to examine the efficacy of slow-frequency rTMS to the frontal cortex in MDD.

METHOD

A literature search was carried out in the databases PubMed and Web of Science in the period between January 1994 and July 2009 with the search terms 'depression' and 'transcranial magnetic stimulation'. Nine double-blind sham-controlled parallel intention-to-treat studies (252 patients) fulfilled inclusion criteria and were entered in a random-effects meta-analysis.

RESULTS

The test for heterogeneity was not significant (QT=9.63, p=0.38). An overall weighted moderate mean effect size (d=0.63, 95% confidence interval=0.03-1.24) for active treatment was observed.

CONCLUSIONS

The findings suggest that slow-frequency rTMS to the frontal cortex is more effective than sham treatment and may be equally effective as fast-frequency rTMS in the treatment of MDD.

[Transcranial magnetic stimulation and cerebral physiology in psychiatric disorders]

BACKGROUND

Transcranial magnetic stimulation (tms) is a technique that is being used increasingly to investigate the biological precursors of psychiatric disorders.

AIM

To survey the current knowledge about deficits in local cerebral physiologic processes, as measured with tms methods in patients with obsessive-compulsive disorder, depression, schizophrenia or attention deficit/ hyperactivity disorder.

METHOD

Aspects of cortical excitability and functional connectivity between the cerebral hemispheres as measured with single and paired-pulse tms were investigated by reviewing the scientific literature. results Obsessive compulsive disorder, depression, schizophrenia and attention deficit/ hyperactivity disorder are found to be associated with aberrant cerebral excitability and impaired functional connectivity.

CONCLUSION

TMS is a suitable tool for examining unique aspects of brain physiology in individuals with a psychiatric condition.

Antidepressant efficacy of high-frequency transcranial magnetic stimulation over the left dorsolateral prefrontal cortex in double-blind sham-controlled designs: a meta-analysis

BACKGROUND

For more than a decade high-frequency repetitive transcranial magnetic stimulation (rTMS) has been applied to the left dorsolateral prefrontal cortex (DLPFC) in search of an alternative treatment for depression. The aim of this study was to provide an update on its clinical efficacy by performing a meta-analysis involving double-blind sham-controlled studies.

METHOD

A literature search was conducted in the databases PubMed and Web of Science in the period between January 1980 and November 2007 with the search terms 'depression' and 'transcranial magnetic stimulation'. Thirty double-blind sham-controlled parallel studies with 1164 patients comparing the percentage change in depression scores from baseline to endpoint of active versus sham treatment were included. A random effects meta-analysis was performed to investigate the clinical efficacy of fast-frequency rTMS over the left DLPFC in depression.

RESULTS

The test for heterogeneity was not significant (QT=30.46, p=0.39). A significant overall weighted mean effect size, d=0.39 [95% confidence interval (CI) 0.25-0.54], for active treatment was observed (z=6.52, p<0.0001). Medication resistance and intensity of rTMS did not play a role in the effect size.

CONCLUSIONS

These findings show that high-frequency rTMS over the left DLPFC is superior to sham in the treatment of depression. The effect size is robust and comparable to at least a subset of commercially available antidepressant drug agents. Current limitations and future prospects are discussed.

TMS Pulses on the Frontal Eye Fields Break Coupling Between Visuospatial Attention and Eye Movements

While preparing a saccadic eye movement, visual processing of the saccade goal is prioritized. Here, we provide evidence that the frontal eye fields (FEFs) are responsible for this coupling between eye movements and shifts of visuospatial attention. Functional magnetic resonance imaging (fMRI)–guided transcranial magnetic stimulation (TMS) was applied to the FEFs 30 ms before a discrimination target was presented at or next to the target of a saccade in preparation. Results showed that the well-known enhancement of discrimination performance on locations to which eye movements are being prepared was diminished by TMS contralateral to eye movement direction. Based on the present and other reports, we propose that saccade preparatory processes in the FEF affect selective visual processing within the visual cortex through feedback projections, in that way coupling saccade preparation and visuospatial attention.

[Is there a big role for the little brain in psychiatry?]

The cerebellum is a structure situated in the posterior cranial fossa. It has long been assumed that the cerebellum is concerned primarily with motor-related functions. However recent research has demonstrated that the cerebellum also plays a role in psychiatric disorders, including schizophrenia, autism and depression. Recent developments, described in this article, suggest that malfunctioning of the cerebellum can lead to severe emotion dysregulation and to psychopathological conditions.

A stereotactic method for image-guided transcranial magnetic stimulation validated with fMRI and motor-evoked potentials

Transcranial Magnetic Stimulation (TMS) delivers short magnetic pulses that penetrate the skull unattenuated, disrupting neural processing in a noninvasive, reversible way. To disrupt specific neural processes, coil placement over the proper site is critical. Therefore, a neural navigator (NeNa) was developed. NeNa is a frameless stereotactic device using structural and functional magnetic resonance imaging (fMRI) data to guide TMS coil placement. To coregister the participant's head to his MRI, 3D cursors are moved to anatomical landmarks on a skin rendering of the participants MRI on a screen, and measured at the head with a position measurement device. A method is proposed to calculate a rigid body transformation that can coregister both sets of coordinates under realistic noise conditions. After coregistration, NeNa visualizes in real time where the device is located with respect to the head, brain structures, and activated areas, enabling precise placement of the TMS coil over a predefined target region. NeNa was validated by stimulating 5 x 5 positions around the 'motor hotspot' (thumb movement area), which was marked on the scalp guided by individual fMRI data, while recording motor-evoked potentials (MEPs) from the abductor pollicis brevis (APB). The distance between the center of gravity (CoG) of MEP responses and the location marked on the scalp overlying maximum fMRI activation was on average less then 5 mm. The present results demonstrate that NeNa is a reliable method for image-guided TMS coil placement.

Cortisol, depression and reduced cortico-cortical cross-talk in Cushing's syndrome

In the present report assumed relationships between hypercortisolism, depression and cortico-cortical cross-talk in Cushing's syndrome were investigated. Electroencephalographic (EEG) recordings and depression ratings from three patients diagnosed with mild, moderate and severe hypercortisolism were obtained. Reductions in cortico-cortical cross-talk as quantified by EEG coherence together with increases in depression were observed in the moderate and severe as compared to the mild hypercorticolism state. These findings provide preliminary evidence for the hypothesis that loss of cortico-cortical cross-talk might be linked to hypercortisolism and the severity of depressive symptoms.