Publications by authors named "Martin Bellander"

11 Publications

  • Page 1 of 1

ACT-enhanced group behavior therapy for trichotillomania and skin-picking disorder: A feasibility study.

J Clin Psychol 2021 Jul 3;77(7):1537-1555. Epub 2021 May 3.

Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institutet, and Stockholm Health Care Services, Region Stockholm, Sweden.

Objective: To evaluate the feasibility and efficacy of ACT-enhanced Group Behavior Therapy (AEGBT) for mixed diagnosis groups including patients with trichotillomania (TTM) and skin-picking disorder (SPD) in routine psychiatric care.

Method: Adult patients (N = 40) with TTM and/or SPD received 10 weeks of AEGBT followed by five booster sessions. The primary outcome measure for TTM was the Massachusetts General Hospital Hairpulling Scale (MGH-HPS) and for SPD the Skin Picking Scale-Revised (SPS-R), assessed at posttreatment and at booster sessions.

Results: Results showed significant reductions in hair pulling and skin-picking severity from baseline to posttreatment and large effect sizes at posttreatment. Improvements remained significant at the 12-month follow-up for patients with SPD, but not for patients with TTM. Group attendance was high and few patients dropped out from treatment. The group format enabled therapists to see 25% more patients compared with an individual format.

Conclusion: The results provide initial support for the feasibility and efficacy of an adapted treatment approach for TTM and SPD.
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http://dx.doi.org/10.1002/jclp.23147DOI Listing
July 2021

A computational reward learning account of social media engagement.

Nat Commun 2021 02 26;12(1):1311. Epub 2021 Feb 26.

Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands.

Social media has become a modern arena for human life, with billions of daily users worldwide. The intense popularity of social media is often attributed to a psychological need for social rewards (likes), portraying the online world as a Skinner Box for the modern human. Yet despite such portrayals, empirical evidence for social media engagement as reward-based behavior remains scant. Here, we apply a computational approach to directly test whether reward learning mechanisms contribute to social media behavior. We analyze over one million posts from over 4000 individuals on multiple social media platforms, using computational models based on reinforcement learning theory. Our results consistently show that human behavior on social media conforms qualitatively and quantitatively to the principles of reward learning. Specifically, social media users spaced their posts to maximize the average rate of accrued social rewards, in a manner subject to both the effort cost of posting and the opportunity cost of inaction. Results further reveal meaningful individual difference profiles in social reward learning on social media. Finally, an online experiment (n = 176), mimicking key aspects of social media, verifies that social rewards causally influence behavior as posited by our computational account. Together, these findings support a reward learning account of social media engagement and offer new insights into this emergent mode of modern human behavior.
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http://dx.doi.org/10.1038/s41467-020-19607-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7910435PMC
February 2021

No Evidence for Improved Associative Memory Performance Following Process-Based Associative Memory Training in Older Adults.

Front Aging Neurosci 2016 9;8:326. Epub 2017 Jan 9.

Aging Research Center, Karolinska Institutet and Stockholm UniversityStockholm, Sweden; Otto Hahn Research Group on Associative Memory in Old Age, Max Planck Institute for Human DevelopmentBerlin, Germany.

Studies attempting to improve episodic memory performance with strategy instructions and training have had limited success in older adults: their training gains are limited in comparison to those of younger adults and do not generalize to untrained tasks and contexts. This limited success has been partly attributed to age-related impairments in associative binding of information into coherent episodes. We therefore investigated potential training and transfer effects of process-based associative memory training (i.e., repeated practice). Thirty-nine older adults ( = 68.8) underwent 6 weeks of either adaptive associative memory training or item recognition training. Both groups improved performance in item memory, spatial memory (object-context binding) and reasoning. A disproportionate effect of associative memory training was only observed for item memory, whereas no training-related performance changes were observed for associative memory. Self-reported strategies showed no signs of spontaneous development of memory-enhancing associative memory strategies. Hence, the results do not support the hypothesis that process-based associative memory training leads to higher associative memory performance in older adults.
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http://dx.doi.org/10.3389/fnagi.2016.00326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5220050PMC
January 2017

Behavioral correlates of changes in hippocampal gray matter structure during acquisition of foreign vocabulary.

Neuroimage 2016 05 23;131:205-13. Epub 2015 Oct 23.

Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden. Electronic address:

Experience can affect human gray matter volume. The behavioral correlates of individual differences in such brain changes are not well understood. In a group of Swedish individuals studying Italian as a foreign language, we investigated associations among time spent studying, acquired vocabulary, baseline performance on memory tasks, and gray matter changes. As a way of studying episodic memory training, the language learning focused on acquiring foreign vocabulary and lasted for 10weeks. T1-weighted structural magnetic resonance imaging and cognitive testing were performed before and after the studies. Learning behavior was monitored via participants' use of a smartphone application dedicated to the study of vocabulary. A whole-brain analysis showed larger changes in gray matter structure of the right hippocampus in the experimental group (N=33) compared to an active control group (N=23). A first path analyses revealed that time spent studying rather than acquired knowledge significantly predicted change in gray matter structure. However, this association was not significant when adding performance on baseline memory measures into the model, instead only the participants' performance on a short-term memory task with highly similar distractors predicted the change. This measure may tap similar individual difference factors as those involved in gray matter plasticity of the hippocampus.
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http://dx.doi.org/10.1016/j.neuroimage.2015.10.020DOI Listing
May 2016

Lower baseline performance but greater plasticity of working memory for carriers of the val allele of the COMT Val¹⁵⁸Met polymorphism.

Neuropsychology 2015 Mar 12;29(2):247-54. Epub 2014 May 12.

Aging Research Center, Karolinska Institutet.

Objective: Little is known about genetic contributions to individual differences in cognitive plasticity. Given that the neurotransmitter dopamine is critical for cognition and associated with cognitive plasticity, we investigated the effects of 3 polymorphisms of dopamine-related genes (LMX1A, DRD2, COMT) on baseline performance and plasticity of working memory (WM), perceptual speed, and reasoning.

Method: One hundred one younger and 103 older adults underwent approximately 100 days of cognitive training, and extensive testing before and after training. We analyzed the baseline and posttest data using latent change score models.

Results: For working memory, carriers of the val allele of the COMT polymorphism had lower baseline performance and larger performance gains from training than carriers of the met allele. There was no significant effect of the other genes or on other cognitive domains.

Conclusions: We relate this result to available evidence indicating that met carriers perform better than val carriers in WM tasks taxing maintenance, whereas val carriers perform better at updating tasks. We suggest that val carriers may show larger training gains because updating operations carry greater potential for plasticity than maintenance operations.
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http://dx.doi.org/10.1037/neu0000088DOI Listing
March 2015

Temporal properties of fear extinction--does time matter?

Behav Neurosci 2013 Feb 10;127(1):59-69. Epub 2012 Dec 10.

Karolinska Institutet, Department of Clinical Neuroscience, Psychology Section, 17177 Stockholm, Sweden.

Fear extinction can be defined as the weakening of the expression of a conditioned response (CR) by extended experience of nonreinforcement. Conceptually, two distinct models have been invoked to account for extinction. R. A. Rescorla and A. R. Wagner (1972, A theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement, in A. H. B. W. F. Prokasy (Ed.), Classical conditioning: II. Current research and theory, pp. 64-99, New York, NY, Appleton-Century-Crofts) postulated that the number of exposure trials is the primary determinant of CR decrement, whereas C. R. Gallistel and J. Gibbon (2000, Time, rate, and conditioning, Psychological Review, Vol. 107, pp. 289-344) proposed that the decisive event is the cumulated exposure time to the nonreinforced conditioned stimulus (CS) elapsed after the last CS reinforcement. We evaluated these two accounts in a human differential fear conditioning study in which CR was measured with the fear-potentiated startle response. Cumulated duration of nonreinforcement fails to explain our findings, whereas the number of trials appeared critical. In fact, many CS trials with a duration shorter than the acquisition CS duration facilitated within-session extinction, but this effect did not predict the recovery of fear.
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http://dx.doi.org/10.1037/a0030892DOI Listing
February 2013

Are fear memories erasable?-reconsolidation of learned fear with fear-relevant and fear-irrelevant stimuli.

Front Behav Neurosci 2012 19;6:80. Epub 2012 Nov 19.

Department of Clinical Neuroscience, Karolinska Institutet Stockholm, Sweden.

Recent advances in the field of fear learning have demonstrated that a single reminder exposure prior to extinction training can prevent the return of extinguished fear by disrupting the process of reconsolidation. These findings have however proven hard to replicate in humans. Given the significant implications of preventing the return of fear, the purpose of the present study was to further study the putative effects of disrupting reconsolidation. In two experiments, we assessed whether extinction training initiated within the reconsolidation time window could abolish the return of fear using fear-relevant (Experiment 1) or fear-irrelevant (Experiment 2) conditioned stimuli (CS). In both experiments, participants went through conditioning, extinction, and reinstatement testing on three consecutive days, with one of two reinforced CS being reactivated 10 min prior to extinction. We found that a single reminder exposure prior to extinction training did not prevent the return of extinguished fear responding using either fear-relevant or fear-irrelevant CSs. Our findings point to the need to further study the specific parameters that enable disruption of reconsolidation.
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http://dx.doi.org/10.3389/fnbeh.2012.00080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3501228PMC
November 2012

Neural correlates of training-related working-memory gains in old age.

Neuroimage 2011 Oct 2;58(4):1110-20. Epub 2011 Jul 2.

Aging Research Center, Karolinska Institute, Stockholm, Sweden.

Working memory (WM) functioning declines in old age. Due to its impact on many higher-order cognitive functions, investigating whether training can modify WM performance has recently been of great interest. We examined the relationship between behavioral performance and neural activity following five weeks of intensive WM training in 23 healthy older adults (M=63.7 years). 12 participants received adaptive training (i.e. individually adjusted task difficulty to bring individuals to their performance maximum), whereas the others served as active controls (i.e. fixed low-level practice). Brain activity was measured before and after training, using fMRI, while subjects performed a WM task under two difficulty conditions. Although there were no training-related changes in WM during scanning, neocortical brain activity decreased post training and these decreases were larger in the adaptive training group than in the controls under high WM load. This pattern suggests intervention-related increases in neural efficiency. Further, there were disproportionate gains in the adaptive training group in trained as well as in non-trained (i.e. attention, episodic memory) tasks assessed outside the scanner, indicating the efficacy of the training regimen. Critically, the degree of training-related changes in brain activity (i.e. neocortical decreases and subcortical increases) was related to the maximum gain score achieved during the intervention period. This relationship suggests that the decreased activity, but also specific activity increases, observed were functionally relevant.
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http://dx.doi.org/10.1016/j.neuroimage.2011.06.079DOI Listing
October 2011

Preliminary evidence that allelic variation in the LMX1A gene influences training-related working memory improvement.

Neuropsychologia 2011 Jun 22;49(7):1938-42. Epub 2011 Mar 22.

Aging Research Center, Karolinska Institute, Stockholm, Gävlegatan 16, SE-11330 Stockholm, Sweden.

LMX1A is a transcription factor involved in the development of dopamine (DA)-producing neurons in midbrain. Previous research has shown that allelic variations in three LMX1A single nucleotide polymorphisms (SNPs) were related to risk of Parkinson's disease (PD), suggesting that these SNPs may influence the number of mesencephalic DA neurons. Prompted by the established link between striatal DA functions and working memory (WM) performance, we examined two of these SNPs in relation to the ability to benefit from 4 weeks of WM training. One SNP (rs4657412) was strongly associated with the magnitude of training-related gains in verbal WM. The allele linked to larger gains has previously been suggested to be associated with higher dopaminergic nerve cell density. No differential gains of either SNP were observed for spatial WM, and the genotype groups were also indistinguishable in tests of attention, interference control, episodic memory, perceptual speed, and reasoning for both SNPs. This pattern of data is in agreement with previous findings from our group, suggesting that cognitive effects of DA-related genes may be more easily detected in a training context than for single-assessment performance scores.
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http://dx.doi.org/10.1016/j.neuropsychologia.2011.03.021DOI Listing
June 2011

Working memory plasticity modulated by dopamine transporter genotype.

Neurosci Lett 2009 Dec 9;467(2):117-20. Epub 2009 Oct 9.

Aging Research Center, Karolinska Institute, Stockholm, Sweden.

Dopamine (DA) is implicated in working memory (WM) functioning. Variations in the DA transporter (DAT1) gene (SLC6A3) regulate DA availability in striatum. Compared to DAT1 9/10-repeat carriers, homozygosity of the DAT1 10-repeat allele has been related to less active dopaminergic pathways. A group of younger adults received 4 weeks of computerized adaptive training on several WM tasks. All participants improved their performance as a function of training. However, DAT1 9/10-repeat carriers showed larger training-related gains than DAT1 10-repeat carriers in visuospatial WM. By contrast, the two groups were indistinguishable in baseline WM performance as well as in a variety of tasks assessing different cognitive abilities. This pattern of results provides novel evidence that WM plasticity is a more sensitive indicator of DAT1 gene-related cognitive differences than single-assessment performance scores.
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http://dx.doi.org/10.1016/j.neulet.2009.10.018DOI Listing
December 2009