A single dose of mirtazapine attenuates neural responses to self-referential processing

The effect of sertraline on emotional processing: secondary analyses of the PANDA randomised controlled trial

BACKGROUND

According to the cognitive neuropsychological model, antidepressants reduce symptoms of depression and anxiety by increasing positive relative to negative information processing. Most studies of whether antidepressants alter emotional processing use small samples of healthy individuals, which lead to low statistical power and selection bias and are difficult to generalise to clinical practice. We tested whether the selective serotonin reuptake inhibitor (SSRI) sertraline altered recall of positive and negative information in a large randomised controlled trial (RCT) of patients with depressive symptoms recruited from primary care.

METHODS

The PANDA trial was a pragmatic multicentre double-blind RCT comparing sertraline with placebo. Memory for personality descriptors was tested at baseline and 2 and 6 weeks after randomisation using a computerised emotional categorisation task followed by a free recall. We measured the number of positive and negative words correctly recalled (hits). Poisson mixed models were used to analyse longitudinal associations between treatment allocation and hits.

RESULTS

A total of 576 participants (88% of those randomised) completed the recall task at 2 and 6 weeks. We found no evidence that positive or negative hits differed according to treatment allocation at 2 or 6 weeks (adjusted positive hits ratio = 0.97, 95% CI 0.90-1.05, p = 0.52; adjusted negative hits ratio = 0.99, 95% CI 0.90-1.08, p = 0.76).

CONCLUSIONS

In the largest individual placebo-controlled trial of an antidepressant not funded by the pharmaceutical industry, we found no evidence that sertraline altered positive or negative recall early in treatment. These findings challenge some assumptions of the cognitive neuropsychological model of antidepressant action.

Escitalopram enhances synchrony of brain responses during emotional narratives in patients with major depressive disorder

One-week treatment with escitalopram decreases amygdala responses to fearful facial expressions in depressed patients, but it remains unknown whether it also modulates processing of complex and freely processed emotional stimuli resembling daily life emotional situations. Inter-subject correlation (ISC) offers a means to track brain activity during complex, dynamic stimuli in a model-free manner. Twenty-nine treatment-seeking patients with major depressive disorder were randomized in a double-blind study design to receive either escitalopram or placebo for one week, after which functional magnetic resonance imaging (fMRI) was performed. During fMRI the participants listened to spoken emotional narratives. Level of ISC between the escitalopram and the placebo group was compared across all the narratives and separately for the episodes with positive and negative valence. Across all the narratives, the escitalopram group had higher ISC in the default mode network of the brain as well as in the fronto-temporal narrative processing regions, whereas lower ISC was seen in the middle temporal cortex, hippocampus and occipital cortex. Escitalopram increased ISC during positive parts of the narratives in the precuneus, medial prefrontal cortex, anterior cingulate and fronto-insular cortex, whereas there was no significant synchronization in brain responses to positive vs negative events in the placebo group. Increased ISC may imply improved emotional synchronization with others, particularly during observation of positive events. Further studies are needed to test whether this contributes to the later therapeutic effect of escitalopram.

Virtual Reality-Based Psychotherapy in Social Anxiety Disorder: fMRI Study Using a Self-Referential Task

BACKGROUND

Although it has been well demonstrated that the efficacy of virtual reality therapy for social anxiety disorder is comparable to that of traditional cognitive behavioral therapy, little is known about the effect of virtual reality on pathological self-referential processes in individuals with social anxiety disorder.

OBJECTIVE

We aimed to determine changes in self-referential processing and their neural mechanisms following virtual reality treatment.

METHODS

We recruited participants with and without a primary diagnosis of social anxiety disorder to undergo clinical assessments (Social Phobia Scale and Post-Event Rumination Scale) and functional magnetic resonance imaging (fMRI) scans. Participants with social anxiety disorder received virtual reality-based exposure treatment for 6 sessions starting immediately after baseline testing. After the sixth session, participants with social anxiety disorder completed follow-up scans during which they were asked to judge whether a series of words (positive, negative, neutral) was relevant to them.

RESULTS

Of 25 individuals with social anxiety disorder who participated in the study, 21 completed the sessions and follow-up; 22 control individuals also participated. There were no significant differences in age (P=.36), sex (P=.71), or handedness (P=.51) between the groups. Whole-brain analysis revealed that participants in the social anxiety disorder group had increased neural responses during positive self-referential processing in the medial temporal and frontal cortexes compared with those in the control group. Participants in the social anxiety disorder group also showed increased left insular activation and decreased right middle frontal gyrus activation during negative self-referential processing. After undergoing virtual reality-based therapy, overall symptoms of the participants with social anxiety disorder were reduced, and these participants exhibited greater activity in a brain regions responsible for self-referential and autobiographical memory processes while viewing positive words during postintervention fMRI scans. Interestingly, the greater the blood oxygen level dependent changes related to positive self-referential processing, the lower the tendency to ruminate on the negative events and the lower the social anxiety following the virtual reality session. Compared with that at baseline, higher activation was also found within broad somatosensory areas in individuals with social anxiety disorder during negative self-referential processing following virtual reality therapy.

CONCLUSIONS

These fMRI findings might reflect the enhanced physiological and cognitive processing in individuals with social anxiety disorder in response to self-referential information. They also provide neural evidence of the effect of virtual reality exposure therapy on social anxiety and self-derogation.

Cognitive neuropsychological theory of antidepressant action: a modern-day approach to depression and its treatment

Depression is a leading cause of disability worldwide and improving its treatment is a core research priority for future programmes. A change in the view of psychological and biological processes, from seeing them as separate to complementing one another, has introduced new perspectives on pathological mechanisms of depression and treatment mode of action. This review presents a theoretical model that incorporated this novel approach, the cognitive neuropsychological hypothesis of antidepressant action. This model proposes that antidepressant treatments decrease the negative bias in the processing of emotionally salient information early in the course of antidepressant treatment, which leads to the clinically significant mood improvement later in treatment. The paper discusses the role of negative affective biases in the development of depression and response to antidepressant treatments. It also discusses whether the model can be applied to other antidepressant interventions and its potential translational value, including treatment choice, prediction of response and drug development.

Trait Sensitivity to Negative and Positive Feedback Does Not Interact With the Effects of Acute Antidepressant Treatment on Hedonic Status in Rats

Aberrant cognition plays a pivotal role in the development and maintenance of depression. One of the most important cognitive distortions associated with depression is aberrant sensitivity to performance feedback. Under clinical conditions, this sensitivity can be measured using the probabilistic reversal learning (PRL) test, which has also been recently implemented in animal studies. Although the evidence for the coexistence of depression and altered feedback sensitivity is relatively coherent, it is unclear whether this sensitivity can influence the effectiveness of antidepressant treatment. In the present research, we investigated how trait sensitivity to negative and positive feedback interacts with the effects of acute antidepressant treatment on hedonic status in rats. We tested a cohort of rats with a series of 10 PRL tests, and based on this screening, we classified each animal as sensitive or insensitive to negative and positive feedback. Subsequently, in the Latin square design, we evaluated the effects of a single administration of two antidepressant drugs (each at three different doses: agomelatine: 5, 10, and 40 mg/kg; mirtazapine 0.5, 1, and 3 mg/kg) on the hedonic status of rats in the sucrose preference tests. There was no statistically significant interaction between trait sensitivity to feedback and the effects of acute antidepressant treatment on hedonic status in rats.

Mirtazapine for chronic breathlessness? A review of mechanistic insights and therapeutic potential

INTRODUCTION

Chronic breathlessness is a common and distressing symptom of advanced disease with few effective treatments. Central nervous system mechanisms are important in respiratory sensation and control. Consequently, drugs which may modify processing and perception of afferent information in the brain may have a role. Antidepressants have been proposed; however, current evidence is limited. Of potentially suitable antidepressants, mirtazapine is an attractive option given its tolerability profile, low cost, and wide availability, along with additional potential benefits. Areas covered: The paper provides an overview of the physiology of breathlessness, with an emphasis on central mechanisms, particularly the role of fear circuits and the associated neurotransmitters. It provides a potential rationale for how mirtazapine may improve chronic breathlessness and quality of life in patients with advanced disease. The evidence was identified by a literature search performed in PubMed through to October 2018. Expert opinion: Currently, there is insufficient evidence to support the routine use of antidepressants for chronic breathlessness in advanced disease. Mirtazapine is a promising candidate to pursue, with definitive randomized controlled trials required to determine its efficacy and safety in this setting.

Cognitive neuropsychological theory: Reconciliation of psychological and biological approaches for depression

New antidepressants and individualized approaches to treatment, matching specific therapies to individual patients, are urgently needed. For this, a better understanding of processes underpinning the development of depressive symptoms and response to medications are required. The cognitive neuropsychological model offers a novel approach uniquely combining biological and psychological approaches to explain how antidepressants exert their effect, why there is a delay in the onset of their clinical effect, and how changes in emotional processing are an essential step for a clinical antidepressant effect to take place. The paper presents the model and its underpinnings in the form of research in both healthy and depressed individuals, as well as the potential for its practical use.

Short-term escitalopram treatment normalizes aberrant self-referential processing in major depressive disorder

BACKGROUND

Increased self-focus and negative self-concept play an important role in depression. Antidepressants influence self-referential processing in healthy volunteers, but their function in self-processing of depressed patients remains unknown.

METHODS

Thirty-two depressed patients were randomly allocated to receive either escitalopram 10 mg or placebo for one week. After one week, neural responses to positive and negative self-referential adjectives and neutral control stimuli were assessed with functional magnetic resonance imaging. A group of matched healthy volunteers served as a control group.

RESULTS

Escitalopram decreased responses of medial fronto-parietal regions to self-referential words relative to non-emotional control stimuli, driven by increased responses to the control condition. Escitalopram also increased responses in the pre-defined region of the medial prefrontal cortex (MPFC) and the anterior cingulate cortex (ACC) to positive relative to negative words. Importantly, the changes in neural responses occurred before any effect on depressive symptoms, implying a direct effect of escitalopram. Furthermore, the placebo group had decreased responses of the MPFC and the ACC to positive self-referential processing relative to the matched healthy controls. However, neural responses of the escitalopram group and the healthy unmedicated controls were similar.

LIMITATIONS

Differences between the groups in self-reported depression symptoms and personality traits may have influenced the results.

CONCLUSION

One-week treatment with escitalopram normalized aberrant self-referential processing in depressed patients, shifting the focus from the self to the external environment and potentiating positive self-referential processing. This may be an important factor in mechanism of action of antidepressants.

Toward a Neuroscience of Adult Cognitive Developmental Theory

Piaget's genetic epistemology has provided the constructivist approach upon which child developmental theories were founded, in that infants are thought to progress through distinct cognitive stages until they reach maturity in their early 20's. However, it is now well established that cognition continues to develop after early adulthood, and several “neo-Piagetian” theories have emerged in an attempt to better characterize adult cognitive development. For example, Kegan's Constructive Developmental Theory (CDT) argues that the thought processes used by adults to construct their reality change over time, and reaching higher stages of cognitive development entails becoming objectively aware of emotions and beliefs that were previously in the realm of the subconscious. In recent years, neuroscience has shown a growing interest in the biological substrates and neural mechanisms encompassing adult cognitive development, because psychological and psychiatric disorders can arise from deficiencies therein. In this article, we will use Kegan's CDT as a framework to discuss adult cognitive development in relation to closely correlated existing constructs underlying social processing, such as the perception of self and others. We will review the functional imaging and electrophysiologic evidence behind two key concepts relating to these posited developmental changes. These include self-related processing, a field that distinguishes between having conscious experiences (“being a self”) and being aware of oneself having conscious experiences (“being aware of being a self”); and theory of mind, which is the objective awareness of possessing mental states such as beliefs and desires (i.e., having a “mind”) and the understanding that others possess mental states that can be different from one's own. We shall see that cortical midline structures, including the medial prefrontal cortex and cingulate gyrus, as well as the temporal lobe, are associated with psychological tasks that test these models. In addition, we will review computational modeling approaches to cognitive development, and show how mathematical modeling can provide insights into how sometimes continuous changes in the neural processing substrate can give rise to relatively discrete developmental stages. Because deficiencies in adult cognitive development can result in disorders such as autism and depression, bridging the gaps between developmental psychology, neuroscience, and modeling has potential implications for clinical practice. As neuromodulation techniques such as deep brain and transcranial stimulation continue to advance, interfacing with these systems may lead to the emergence of novel investigational methods and therapeutic strategies in adults suffering from developmental disorders.

Single dose of mirtazapine modulates whole-brain functional connectivity during emotional narrative processing

The link between neurotransmitter-level effects of antidepressants and their clinical effect remain poorly understood. A single dose of mirtazapine decreases limbic responses to fearful faces in healthy subjects, but it is unknown whether this effect applies to complex emotional situations and dynamic connectivity between brain regions. Thirty healthy volunteers listened to spoken emotional narratives during functional magnetic resonance imaging (fMRI). In an open-label design, 15 subjects received 15mg of mirtazapine two hours prior to fMRI while 15 subjects served as a control group. We assessed the effects of mirtazapine on regional neural responses and dynamic functional connectivity associated with valence and arousal. Mirtazapine attenuated responses to unpleasant events in the right fronto-insular cortex, while modulating responses to arousing events in the core limbic regions and the cortical midline structures (CMS). Mirtazapine decreased responses to unpleasant and arousing events in sensorimotor areas and the anterior CMS implicated in self-referential processing and formation of subjective feelings. Mirtazapine increased functional connectivity associated with positive valence in the CMS and limbic regions. Mirtazapine triggers large-scale changes in regional responses and functional connectivity during naturalistic, emotional stimuli. These span limbic, sensorimotor, and midline brain structures, and may be relevant to the clinical effectiveness of mirtazapine.

Resting-state brain alteration after a single dose of SSRI administration predicts 8-week remission of patients with major depressive disorder

BACKGROUND

The present study investigated alteration of brain resting-state activity induced by antidepressant treatment and attempted to investigate whether treatment efficacy can be predicted at an early stage of pharmacological treatment.

METHOD

Forty-eight first-episode medication-free patients diagnosed with major depression received treatment with escitalopram. Resting-state functional magnetic resonance imaging was administered prior to treatment, 5 h after the first dose, during the course of pharmacological treatment (week 4) and at endpoint (week 8). Resting-state activity was evaluated in the course of the 8-week treatment and in relation to clinical improvement.

RESULTS

Escitalopram dynamically modified resting-state activity in depression during the treatment. After 5 h the antidepressant induced a significant decrease in the signal in the occipital cortex and an increase in the dorsolateral and dorsomedial prefrontal cortices and middle cingulate cortex. Furthermore, while remitters demonstrated more obvious changes following treatment, these were more modest in non-responders suggesting possible tonic and dynamic differences in the serotonergic system. Changes after 5 h in the caudate, occipital and temporal cortices were the best predictor of clinical remission at endpoint.

CONCLUSIONS

This study revealed the possibility of using the measurement of resting-state neural changes a few hours after acute administration of antidepressant to identify individuals likely to remit after a few weeks of treatment.