Alexander V Lebedev

Alexander V Lebedev
Karolinska Institutet | KI · Department of Clinical Neuroscience

MD, PhD

About

61
Publications
45,593
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,242
Citations
Introduction
Alexander Lebedev is an assistant professor at the Department of Clinical Neuroscience (Karolinska Institutet, Sweden). He received his MD and psychiatry training from the St. Petersburg State Medical University in 2010, and PhD from the University of Bergen, Norway in 2014. Interests: higher cognition, creativity, psychosis, psychopharmacology
Additional affiliations
October 2012 - August 2014
University of Bergen
Position
  • Computer-assisted diagnosis of dementia and its neuropsychiatric symptoms
August 2011 - November 2014
Stavanger University Hospital
Position
  • Computer-assisted diagnosis of dementia and its neuropsychiatric symptoms
September 2008 - present
St. Petersburg Military Medical Academy
Position
  • Multimodal study of depression
Description
  • Neuroimaging, fMRI, PET, DTI, depression, TRD
Education
September 2010 - July 2011
I.P. Pavlov State Medical University
Field of study
September 2008 - July 2010
I.P. Pavlov State Medical University
Field of study
August 2003 - August 2008
St. Petersburg Military Military Medical Academy
Field of study

Publications

Publications (61)
Article
Personality is known to be relatively stable throughout adulthood. Nevertheless, it has been shown that major life events with high personal significance, including experiences engendered by psychedelic drugs, can have an enduring impact on some core facets of personality. In the present, balanced-order, placebo-controlled study, we investigated bi...
Article
Ego-disturbances have been a topic in schizophrenia research since the earliest clinical descriptions of the disorder. Manifesting as a feeling that one's "self," "ego," or "I" is disintegrating or that the border between one's self and the external world is dissolving, "ego-disintegration" or "dissolution" is also an important feature of the psych...
Article
Full-text available
The aim of this study was to assess whether mild cognitive impairment (MCI) is associated with disruption in large-scale structural networks in newly diagnosed, drug-naïve patients with Parkinson's disease (PD). Graph theoretical analyses were applied to 3T MRI data from 123 PD patients and 56 controls from the Parkinson's progression markers initi...
Article
Full-text available
Cognitive impairment is a common non-motor feature of Parkinson’s disease (PD). The current study aimed to investigate resting state fMRI correlates of cognitive impairment in PD from a large-scale network perspective, and to assess the impact of dopamine deficiency on these networks. Thirty PD patients with resting state fMRI were included from th...
Article
Full-text available
Context Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB) are the most common neurodegenerative dementia types. It is important to differentiate between them because of the differences in prognosis and treatment approaches. Objective Investigate if sparse partial least squares (SPLS) classification of cortical thickness measurements coul...
Article
Full-text available
Balance dysfunction is a disabling symptom in people with Parkinson’s disease (PD). Evidence suggests that exercise can improve balance performance and induce neuroplastic effects. We hypothesised that a 10-week balance intervention (HiBalance) would improve balance, other motor and cognitive symptoms, and alter task-evoked brain activity in people...
Article
Delusional beliefs consist of strong priors characterized by resistance to change even when evidence supporting another view is overwhelming. Such bias against disconfirmatory evidence (BADE) has been experimentally demonstrated in patients with psychosis as well as in delusion proneness. In this fMRI-study, we tested for similar resistance to chan...
Article
Full-text available
Psychosis is associated with distorted perceptions and deficient bottom-up learning such as classical fear conditioning. This has been interpreted as reflecting imprecise priors in low-level predictive coding systems. Paradoxically, overly strong beliefs, such as overvalued beliefs and delusions, are also present in psychosis-associated states. In...
Article
Full-text available
The stock market is a bellwether of socio-economic changes that may directly affect individual well-being. Using large-scale UK-biobank data generated over 14 years, we applied specification curve analysis to rigorously identify significant associations between the local stock market index (FTSE100) and 479,791 UK residents’ mood, as well as their...
Article
Background Bipolar disorder (BD) is associated with cortical and subcortical structural brain abnormalities. It is unclear whether such alterations progressively change over time, and how this is related to the number of mood episodes. To address this question, we analyzed a large and diverse international sample with longitudinal magnetic resonanc...
Preprint
Full-text available
The stock market is a bellwether of socio-economic changes that may directly affect individual well-being. Using large-scale UK-biobank data generated over 14 years, we applied specification curve analysis to rigorously identify significant associations between the local stock market index (FTSE100) and 479,791 UK residents’ mood, as well as their...
Article
Full-text available
VO2max (maximal oxygen consumption), a validated measure of aerobic fitness, has been associated with better cerebral artery compliance and measures of brain morphology, such as higher cortical thickness (CT) in frontal, temporal and cingular cortices, and larger grey matter volume (GMV) of the middle temporal gyrus, hippocampus, orbitofrontal cort...
Article
Full-text available
Despite recently resurrected scientific interest in classical psychedelics, few studies have focused on potential harms associated with abuse of these substances. In particular, the link between psychedelic use and psychotic symptoms has been debated while no conclusive evidence has been presented. Here, we studied an adult population (n = 1032) wi...
Article
Full-text available
It has previously been demonstrated that short-term foreign language learning can lead to structural brain changes in younger adults. Experience-dependent brain plasticity is known to be possible also in older age, but the specific effect of foreign language learning on brain structure in language-and memory-relevant regions in the old brain remain...
Article
Full-text available
We investigated the feasibility aspects of two choice reaction time tasks designed to assess implicit sequence learning and dual task ability in individuals with mild to moderate Parkinson's disease in comparison to healthy individuals. Twelve individuals with mild to moderate Parkinson's disease and 12 healthy individuals, all ≥ 60 years of age, w...
Article
Full-text available
Genetic and hormonal factors have been suggested to influence human sexual orientation. Previous studied proposed brain differences related to sexual orientation and that these follow cross‐sex shifted patterns. However, the neurobiological correlates of sexual orientation and how genetic factors relate to brain structural variation remains largely...
Article
Full-text available
Background Regular physical activity is beneficial for cognitive performance in older age. A single bout of aerobic physical exercise can transiently improve cognitive performance. Researchers have advanced improvements in cerebral circulation as a mediator of long-term effects of aerobic physical exercise on cognition, but the immediate effects of...
Article
Full-text available
Objective Pedophilic disorder (PD) is characterized by persistent sexual interest in prepubertal children causing distress and increasing the risk for child sexual abuse. Although prior research suggests that PD has neurodevelopmental underpinnings, the evidence remains sparse. To aid the understanding of etiology and treatment development, we quan...
Article
Full-text available
Cognitive aging creates major individual and societal burden, motivating search for treatment and preventive care strategies. Behavioural interventions can improve cognitive performance in older age, but effects are small. Basic research has implicated dopaminergic signalling in plasticity. We investigated whether supplementation with the dopamine-...
Article
Full-text available
Multidomain lifestyle interventions represents a promising strategy to counteract cognitive decline in older age. Brain-derived neurotrophic factor (BDNF) is essential for experience-dependent plasticity and increases following physical exercise, suggesting that physical exercise may facilitate subsequent learning. In a randomized-controlled trial,...
Article
The dorsolateral prefrontal cortex (DLPFC) is part of a network important for emotional regulation and the possibility of modulating activity in this region with transcranial direct current stimulation (TDCS) to change mood has gained great interest, particularly for application in clinical populations. Whilst results in major depressive disorder h...
Article
Full-text available
Background: Parkinson's disease (PD) affects many physiological systems essential for balance control. Recent studies suggest that intensive and cognitively demanding physical exercise programs are capable of inducing plastic brain changes in PD. We have developed a highly challenging balance training (the HiBalance) program that emphasizes critic...
Preprint
Multidomain lifestyle interventions have been identified as a promising strategy to counteract cognitive decline in older age but mechanistic accounts for how such interventions should be designed are lacking. Brain-derived neurotrophic factor is essential for experience-dependent plasticity and increases transiently following physical exercise, su...
Preprint
The dorsolateral prefrontal cortex (DLPFC) is part of a network important for emotional regulation and the possibility of modulating activity in this region with transcranial direct current stimulation (TDCS) to change mood has gained great interest, particularly for application in clinical populations. Whilst results in major depressive disorder h...
Preprint
It has previously been demonstrated that short-term foreign language learning can trigger structural brain changes in younger adults. Experience-dependent brain plasticity is known to be possible also in older age, but the specific effect of foreign language learning on brain structure in language- and memory-relevant regions in the old brain remai...
Preprint
Full-text available
Background: Cognitive aging creates major individual and societal burden, motivating search for treatment and preventive care strategies. Behavioural interventions can improve cognitive performance in older age, but effects are small. Basic research has implicated dopaminergic signaling in plasticity. We investigated whether transient enhancement o...
Article
Researchers have proposed that solving complex reasoning problems, a key indicator of fluid intelligence, involves the same cognitive processes as solving working memory tasks. This proposal is supported by an overlap of the functional brain activations associated with the two types of tasks and by high correlations between interindividual differen...
Preprint
Full-text available
Researchers have proposed that solving complex reasoning problems, a key indicator of fluid intelligence, involves the same cognitive processes as solving working memory tasks. This proposal is supported by an overlap of the functional brain activations associated with the two types of tasks and by high correlations between inter-individual differe...
Article
The promise of transcranial direct-current stimulation (tDCS) as a modulator of cognition has appealed to researchers, media, and the general public. Researchers have suggested that tDCS may increase effects of cognitive training. In this study of 123 older adults, we examined the interactive effects of 20 sessions of anodal tDCS over the left pref...
Article
Full-text available
Transcranial direct current stimulation (tDCS) has been put forward as a non-pharmacological alternative for alleviating cognitive decline in old age. Although results have shown some promise, little is known about the optimal stimulation parameters for modulation in the cognitive domain. In this study, the effects of tDCS over the dorsolateral pre...
Article
Full-text available
Computer-aided diagnosis of Alzheimer's disease (AD) is a rapidly developing field of neuroimaging with strong potential to be used in practice. In this context, assessment of models' robustness to noise and imaging protocol differences together with post-processing and tuning strategies are key tasks to be addressed in order to move towards succes...
Article
Full-text available
The goal of the MLSP 2014 Classification Challenge was to automatically detect subjects with schizophrenia and schizoaffective disorder based on multimodal features derived from the magnetic resonance imaging (MRI) data. The patients with age range of 18-65 years were diagnosed according to DSM-IV criteria. The training data consisted of 46 patient...
Article
Cognitive impairment in Parkinson's disease (PD) is common and does directly impact patients' everyday functioning. However, the underlying mechanisms of early cognitive decline are not known. This study explored the association between striatal dopaminergic deficits and cognitive impairment within a large cohort of early, drug-naïve PD patients an...
Article
Our aim was to assess cortical thickness in a large multicenter cohort of drug-naive patients with early Parkinson disease (PD), with and without mild cognitive impairment (MCI), and explore the cognitive correlates of regional cortical thinning. One hundred twenty-three newly diagnosed patients with PD and 56 healthy controls with 3-tesla structur...
Article
Objective To examine neuroanatomical changes associated with depressive symptoms in Alzheimer's disease (AD) and the relationship between brain structure and cerebrospinal fluid (CSF) AD biomarkers in depressed and non-depressed patients. Methods Two independent cohorts were used in this study. The first cohort (KI) was collected from the Memory C...
Conference Paper
Introduction. Major depressive disorder (MDD) is associated with low frustration tolerance, which is a risk factor for suicide. Hippocampal structural and functional abnormalities have been documented to play one of the crucial roles in the pathophysiology of depression. Recent studies have revealed functional differentiation of the hippocampus. Th...
Conference Paper
Introduction. Depression is common in the elderly with a significant impact on the quality of life, and increased risk for developing dementia. However, the underlying structural brain changes are not well established. Objectives. To investigate neuroanatomical correlates of depressive symptoms in elderly people with and without mild cognitive impa...
Conference Paper
Full-text available
The paper considers a conformal prediction method for bounded regression task. A predictor was based on the Defensive Forecast algorithm and has been applied for a medical prognostic problem. These empirical results are compared and discussed. © IFIP International Federation for Information Processing 2013.
Article
Depression is common in dementia, especially in the early stages, with important clinical implications, but the etiology is unknown and most likely heterogeneous. Antidepressant use in the elderly without dementia has previously been shown to be associated with high risks of adverse events and with structural brain alterations. To investigate corti...
Conference Paper
Full-text available
Objectives: Depression is common in Alzheimer's disease (AD) with important clinical implications, but the etiology is not known. Here we investigate structural cortical changes associated with depression in AD. Methods: 30 subjects (15 with depression and 15 non-depressed matched for age, gender and cognitive impairment) with mild probable AD, def...
Article
Full-text available
Рассматриваются возможности статистического параметрического картирования для анализа структурных [анатомическая магнитно-резонансная томография (МРТ), диффузионно-тензорная визуализация] и функциональных (функциональная МРТ) нейровизуализационных данных на примере исследования депрессивных расстройств. Выпуск журнала "Биотехносфера" № 3 (9)/2010...
Article
Full-text available
Рассматриваются возможности статистического параметрического картирования для анализа структурных [анатомическая магнитно-резонансная томография (МРТ), диффузионно-тензорная визуализация] и функциональных (функциональная МРТ) нейровизуализационных данных на примере исследования депрессивных расстройств. Выпуск журнала "Биотехносфера" № 3 (9)/2010...
Conference Paper
Aims: To develop the clinical–physiological approach to the selection of therapy strategies in resistant anxious–obsessive disorders Methods: Positron emission tomography, functional MRI, magnetic resonance spectroscopy and neurosurgery Results: We summarise the literature data and our own observations from functional neuroimaging and neurosurgic...

Questions

Questions (11)
Question
Dear Colleagues,
I am about to start working with some aversive learning paradigms in humans and wanted to ask for some suggestions on measuring fear responses to threat/mild pain stimuli. 
Specifically, I wonder if you could share some tricks and tips on how to improve quality and reliability of galvanic skin response (which, I know, is inherently noisy and can be tricky to collect in some subjects) or maybe recommend some good ways/techniques to complement it (e.g. by combining with heart rate variability, etc).
Many thanks in advance!
Question
Dear Colleagues,
I wonder if anyone can recommend a specific pipeline for diffusion MRI data preprocessing with subsequent reconstruction of adjacency matrices. Preferably, with step-by-step instructions and straightforward strategy for scripting/running multiple subjects.
I would also appreciate if you could suggest an optimal tractography algorithm to do this for 70-direction, b=2200 s/mm2 diffusion data.
Thank you very much in advance!
Question
Dear Colleagues,
I have recently found a very nice "Ego Pathology Inventory" based on Karl Jaspers' domains of self-consciousness (Scharfetter, 1981).
Can anyone confirm that the correct scoring strategy is just to sum up all "yes" answers per domain (e.g., 3 "yes" and 2 "no" answers to questions 10-14 imply score 3 in the "Consistency/coherence" domain).
Or is it 1-to-4-point scoring? (i.e. "amost never" [1],  "sometimes" [2], "often" [3] "almost always" [4])
Question
I wonder if anyone has ever experienced running graph theoretical (GT) analysis for task fMRI. If so, what are the general recommendations, precautions, pitfalls?
For instance, given that for this kind of analysis long sessions are strongly recommended, do you suggest to acquire images during a particular task within one large block, or do you think it is still better to use a regular block design, then "cut" the data and reconstruct connectivity matrices for different conditions separately? What would be the recommended block length then?
Question
Dear Colleagues,
I would like to discuss the following questions pertaining to the so-called fMRI data scrubbing (http://www.humanconnectome.org/hosted/docs/Power-et-al-NeuroImage.pdf):
1. How and when do you think it is better to do scrubbing (e.g., Is it better to remove spikes before/after bandpass filtering, before independent component analysis or prior to functional connectivity analysis [for example, with mancovan]?)
2. How many volumes associated with "bad event" do you usually remove? (e.g., only 1 volume, or also neighbouring volumes)
3. How do you threshold your scrubbing? (e.g. FD-threshold=0.5mm)
4. Do you interpolate between your time-points afterwards? If so - how? (Nearest Neighbour, Linear, Cubic Spline)
5. When do you exclude a subject from the analysis completely? (e.g., how many volumes one should miss in %s?)
Any comments and suggestions are very welcomed.
Question
I am currently trying to threshold my SPM t-maps with AlphaSim (REST toolbox implementation) that employs Monte Carlo simulations for the control of types I and II errors.
I have a question pertaining to the values that I should put into viewer after the simulation is done in order to set an appropriate threshold…
My original voxel size is 3.3x3.3x.3.3. Diagonal is about 4.67 - so I set 5 as radius in AlphaSim (Cluster Connectivity criterion).
Smoothness was estimated at 7.
I run 5 000 simulations with individual threshold of 0.05 (using my t-maps and mask.img) and got these values (full report is attached):
Cl Size Frequency Cum Prop p/Voxel Max Freq Alpha
1 24096 0.100189 0.046730 0 1.000000
2 17288 0.172071 0.046606 0 1.000000
3 12540 0.224211 0.046429 0 1.000000
1060 0 0.999796 0.000314 0 0.049000
(I Assume this is a cluster size that I should use.)
So, now I should set my p-value to 0.05 and select cluster-size of 1060 voxels.. Am I right?

Network

Cited By

Projects

Project (1)
Project
1) To better understand possible implicit learning and dual task deficits in Parkinsons disease, including neural correaltes (MRI) 2) Investigating the effects of intensive physical exercise, in comparison to voice and speech exercises, on motor abilities and dual task ability in PD with both behavioral outcomes and neural correlates (MRI).