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Reliability of dynamic causal modelling of resting-state magnetoencephalography.
This study assesses the reliability of resting-state dynamic causal modelling (DCM) of magnetoencephalography (MEG) under conductance-based canonical microcircuit models, in terms of both posterior parameter estimates and model evidence. We use resting-state MEG data from two sessions, acquired 2 weeks apart, from a cohort with high between-subject variance arising from Alzheimer's disease. Our focus is not on the effect of disease, but on the reliability of the methods (as within-subject between-session agreement), which is crucial for future studies of disease progression and drug intervention. To assess the reliability of first-level DCMs, we compare model evidence associated with the covariance among subject-specific free energies (i.e., the 'quality' of the models) with versus without interclass correlations. We then used parametric empirical Bayes (PEB) to investigate the differences between the inferred DCM parameter probability distributions at the between subject level. Specifically, we examined the evidence for or against parameter differences (i) within-subject, within-session, and between-epochs; (ii) within-subject between-session; and (iii) within-site between-subjects, accommodating the conditional dependency among parameter estimates. We show that for data acquired close in time, and under similar circumstances, more than 95% of inferred DCM parameters are unlikely to differ, speaking to mutual predictability over sessions. Using PEB, we show a reciprocal relationship between a conventional definition of 'reliability' and the conditional dependency among inferred model parameters. Our analyses confirm the reliability and reproducibility of the conductance-based DCMs for resting-state neurophysiological data. In this respect, the implicit generative modelling is suitable for interventional and longitudinal studies of neurological and psychiatric disorders.
A Neural Decision Signal during Internal Sampling from Working Memory in Humans.
How humans transform sensory information into decisions that steer purposeful behavior is a central question in psychology and neuroscience that is traditionally investigated during the sampling of external environmental signals. The decision-making framework of gradual information sampling toward a decision has also been proposed to apply when sampling internal sensory evidence from working memory. However, neural evidence for this proposal remains scarce. Here we show (using scalp EEG in male and female human volunteers) that sampling internal visual representations from working memory elicits a scalp EEG potential associated with gradual evidence accumulation-the central parietal positivity. Consistent with an evolving decision process, we show how this signal (1) scales with the time participants require to reach a decision about the cued memory content and (2) is amplified when having to decide among multiple contents in working memory. These results bring the electrophysiology of decision-making into the domain of working memory and suggest that variability in memory-guided behavior may be driven (at least in part) by variations in the sampling of our inner mental contents.
Multifaceted consequences of visual distraction during natural behaviour.
Visual distraction is a ubiquitous aspect of everyday life. Studying the consequences of distraction during temporally extended tasks, however, is not tractable with traditional methods. Here we developed a virtual reality approach that segments complex behaviour into cognitive subcomponents, including encoding, visual search, working memory usage, and decision-making. Participants copied a model display by selecting objects from a resource pool and placing them into a workspace. By manipulating the distractibility of objects in the resource pool, we discovered interfering effects of distraction across the different cognitive subcomponents. We successfully traced the consequences of distraction all the way from overall task performance to the decision-making processes that gate memory usage. Distraction slowed down behaviour and increased costly body movements. Critically, distraction increased encoding demands, slowed visual search, and decreased reliance on working memory. Our findings illustrate that the effects of visual distraction during natural behaviour can be rather focal but nevertheless have cascading consequences.
Goal-Dependent Use of Temporal Regularities to Orient Attention under Spatial and Action Uncertainty.
The temporal regularities in our environments support the proactive dynamic anticipation of relevant events. In visual attention, one important outstanding question is whether temporal predictions must be linked to predictions about spatial locations or motor plans to facilitate behaviour. To test this, we developed a task for manipulating temporal expectations and task relevance of visual stimuli appearing within rapidly presented streams, while stimulus location and responding hand remained uncertain. Differently coloured stimuli appeared in one of two concurrent (left and right) streams with distinct temporal probability structures. Targets were defined by colour on a trial-by-trial basis and appeared equiprobably in either stream, requiring a localisation response. Across two experiments, participants were faster and more accurate at detecting temporally predictable targets compared to temporally unpredictable targets. We conclude that temporal expectations learned incidentally from temporal regularities can be called upon flexibly in a goal-driven manner to guide behaviour. Moreover, we show that visual temporal attention can facilitate performance in the absence of concomitant spatial or motor expectations in dynamically unfolding contexts.
Parent-led cognitive behaviour therapy for child anxiety problems: overcoming challenges to increase access to effective treatment.
BACKGROUND: Anxiety problems have a particularly early age of onset and are common among children. As we celebrate the anniversary of the BABCP, it is important to recognise the huge contribution that cognitive behavioural therapy (CBT) has made to the treatment of anxiety problems in children. CBT remains the only psychological intervention for child anxiety problems with a robust evidence base, but despite this, very few children with anxiety problems access CBT. Creative solutions are urgently needed to ensure that effective treatments can be delivered at scale. Here we focus on parent-led CBT as this offers a potential solution that is brief and can be delivered by clinicians without highly specialised training. Over the last decade there has been a substantial increase in randomised controlled trials evaluating this approach with consistent evidence of effectiveness. Nonetheless clinicians, and parents, often have concerns about trying the approach and can face challenges in its delivery. METHOD: We draw on empirical evidence and our clinical experience to address some of these common concerns and challenges, with particular emphasis on the key principles of empowering parents and working with them to provide opportunities for new learning for their children. CONCLUSIONS: We conclude by highlighting some important directions for future research and practice, including further evaluation of who does and does not currently benefit from the approach, determining how it should be adapted to optimise outcomes among groups that may not currently get maximum benefits and across cultures, and capitalising on recent technological developments to increase engagement and widen access.
Relationship of subjective and objective cognition with post-stroke mood differs between early and long-term stroke.
Objective: Depression and anxiety affects approximately 1 in 3 stroke survivors. Performance on standardized objective cognitive tests and self-reported subjective cognitive symptoms are associated with concurrent depression and anxiety, but longitudinal data on whether and how objective and subjective cognition relate to emotional outcomes are lacking. Method: N = 99 stroke survivors (M age = 68.9, SD = 13.1; Median NIH Stroke Severity = 5) completed measures of depression and anxiety (Hospital Anxiety and Depression Scale; HADS), objective cognition (Oxford Cognitive Screen) and subjective cognitive symptoms (Cognitive Failures Questionnaire) at 6-months, 4.5, and 5.5 years post-stroke. The contribution of objective and subjective cognition to depression and anxiety was determined via mixed-effects models. Results: We found no evidence that age, stroke severity, years of education, and participant sex related to changes in HADS-Depression or HADS-Anxiety scores (Marginal R2=0.03 and 0.05, respectively). Objective cognitive impairments at 6-months and increases in subjective cognitive symptoms at 5.5 years significantly related to increased HADS-Depression scores (Marginal R2=0.22). Only increases in subjective cognitive symptoms at 5.5 years significantly related to increased HADS-Anxiety scores (Marginal R2=0.20). When conducting models in reverse, HADS-Depression and HADS-Anxiety scores did not reciprocally explain changes in subjective cognitive symptoms. Conclusions: Objective cognitive abilities are more strongly associated with depression at 6-months post-stroke, while subjective cognitive symptoms are more relevant to both long-term post-stroke depression and anxiety. There may be a unique unidirectional influence of subjective cognitive symptoms to post-stroke depression and anxiety.
Post-stroke fatigue severity is associated with executive dysfunction in chronic stroke.
Following stroke, fatigue is highly prevalent and managing fatigue is consistently rated a key unmet need by stroke survivors and professionals. Domain-specific cognitive impairments have been associated with greater fatigue severity in earlier stages of stroke recovery, but it is unclear whether these associations hold in chronic (>2 years) stroke. The present cross-sectional observational study evaluates the relationship between domain-specific cognitive functioning and the severity of self-reported fatigue among chronic stroke survivors. Participants (N = 105; mean age = 72.92, 41.90% female; mean years post-stroke = 4.57) were assessed in domains of attention (Hearts Cancellation test), language (Boston Naming Test), episodic memory (Logical Memory Test), working memory (Digit Span Backwards task), and executive functioning (set-shifting: Trail Making Test, Part B), as part of the OX-CHRONIC study, a longitudinal stroke cohort. Fatigue was assessed using the Fatigue Severity Scale. In a multiple linear regression analysis inclusive of above cognitive domains, only poorer executive functioning was associated with increased fatigue severity. This provides insight into the cognitive impairment profile of post-stroke fatigue long-term after stroke, with executive functioning deficits as the key hallmark.
Strongly masked content retained in memory made accessible through repetition
A growing body of evidence indicates that information can be stored even in the absence of conscious awareness. Despite these findings, unconscious memory is still poorly understood with limited evidence for unconscious iconic memory storage. Here we show that strongly masked visual data can be stored and accumulate to elicit clear perception. We used a repetition method across a wide range of conditions (Experiment 1) and a more focused follow-up experiment with enhanced masking conditions (Experiment 2). Information was stored despite being masked, demonstrating that masking did not erase or overwrite memory traces but limited perception. We examined the temporal properties and found that stored information followed a gradual but rapid decay. Extraction of meaningful information was severely impaired after 300 ms, and most data was lost after 700 ms. Our findings are congruent with theories of consciousness that are based on an integration of subliminal information and support theoretical predictions based on the global workspace theory of consciousness, especially the existence of an implicit iconic memory buffer store.
Further evidence and theoretical framework for a subliminal sensory buffer store (SSBS)
We recently provided evidence that strongly masked stimuli are not erased or overwritten but are briefly stored in a subliminal sensory buffer store (SSBS), where information can accumulate through repetition and become consciously accessible. SSBS supports a direct prediction made by the global workspace theory of consciousness (GWT) and has implications on discussions about conscious overflow and the problem of the criterion. Here we show that the presentation sequence and the time from the target presentation to evaluation does not significantly impact perception. We suggest that selected information from this subliminal sensory buffer store is transferred into a type of supraliminal short-term memory that keeps stable representations for longer durations with full conscious access. We argue that the level of conscious access of memory storage has a greater impact on subsequent reportability than initial phenomenology and needs to be included more prominently in discussions on perception and consciousness.
Amyloid-dependent and amyloid-independent effects of Tau in individuals without dementia.
OBJECTIVE: To investigate the relationship between the topography of amyloid-β plaques, tau neurofibrillary tangles, and the overlap between the two, with cognitive dysfunction in individuals without dementia. METHODS: We evaluated 154 individuals who were assessed with amyloid-β PET with [18 F]AZD4694, tau-PET with [18 F]MK6240, structural MRI, and neuropsychological testing. We also evaluated an independent cohort of 240 individuals who were assessed with amyloid-β PET with [18 F]Florbetapir, tau-PET with [18 F]Flortaucipir, structural MRI, and neuropsychological testing. Using the VoxelStats toolbox, we conducted voxel-wise linear regressions between amyloid-PET, tau-PET, and their interaction with cognitive function, correcting for age, sex, and years of education. RESULTS: In both cohorts, we observed that tau-PET standardized uptake value ratio in medial temporal lobes was associated with clinical dementia rating Sum of Boxes (CDR-SoB) scores independently of local amyloid-PET uptake (FWE corrected at p
Laterality indices consensus initiative (LICI): A Delphi expert survey report on recommendations to record, assess, and report asymmetry in human behavioural and brain research.
Laterality indices (LIs) quantify the left-right asymmetry of brain and behavioural variables and provide a measure that is statistically convenient and seemingly easy to interpret. Substantial variability in how structural and functional asymmetries are recorded, calculated, and reported, however, suggest little agreement on the conditions required for its valid assessment. The present study aimed for consensus on general aspects in this context of laterality research, and more specifically within a particular method or technique (i.e., dichotic listening, visual half-field technique, performance asymmetries, preference bias reports, electrophysiological recording, functional MRI, structural MRI, and functional transcranial Doppler sonography). Experts in laterality research were invited to participate in an online Delphi survey to evaluate consensus and stimulate discussion. In Round 0, 106 experts generated 453 statements on what they considered good practice in their field of expertise. Statements were organised into a 295-statement survey that the experts then were asked, in Round 1, to independently assess for importance and support, which further reduced the survey to 241 statements that were presented again to the experts in Round 2. Based on the Round 2 input, we present a set of critically reviewed key recommendations to record, assess, and report laterality research for various methods.
Does the autism phenotype differ when selecting groups by neurodevelopmental versus genetic diagnosis? An observational study comparing autism and sex chromosome trisomy.
Background: Autism is diagnosed on the basis of social and non-social behavioural features that are assumed to cluster together, and assumed to be distinct from other aspects of development, such as language ability. It is unclear, however, if these assumptions are valid. This study presents a novel approach to answering this question by investigating whether correlations between autism features are similar for groups selected on behavioural versus genetic diagnosis. Methods: The autism phenotype was assessed by diagnostic interview in young people aged 7 to 14 diagnosed with autism ( N=61) or sex chromosome trisomy (SCT; N=49). Data were analysed by confirmatory factor analysis and MANOVA. Results: Autism features showed a similar factor structure and were distinct from language ability in both groups. However, the SCT group was more likely to show clinically-significant difficulties in just some aspects of autism and a lower level of non-social autism features for their social-communication disabilities. Conclusions: We suggest the group differences emerged because autism diagnostic criteria do not map exactly on the autism phenotype as it manifests "naturally". Conventional diagnostic criteria for autism miss those with uneven profiles of difficulty and those with relatively low levels of restricted and repetitive behaviours and interests.
Can we shift belief in the 'Law of Small Numbers'?
'Sample size neglect' is a tendency to underestimate how the variability of mean estimates changes with sample size. We studied 100 participants, from science or social science backgrounds, to test whether a training task showing different-sized samples of data points (the 'beeswarm' task) can help overcome this bias. Ability to judge if two samples came from the same population improved with training, and 38% of participants reported that they had learned to wait for larger samples before making a response. Before and after training, participants completed a 12-item estimation quiz, including items testing sample size neglect (S-items). Bonus payments were given for correct responses. The quiz confirmed sample size neglect: 20% of participants scored zero on S-items, and only two participants achieved more than 4/6 items correct. Performance on the quiz did not improve after training, regardless of how much learning had occurred on the beeswarm task. Error patterns on the quiz were generally consistent with expectation, though there were some intriguing exceptions that could not readily be explained by sample size neglect. We suggest that training with simulated data might need to be accompanied by explicit instruction to be effective in counteracting sample size neglect more generally.
Testing the relationship between lateralization on sequence-based motor tasks and language laterality using an online battery.
ABSTRACTStudies have highlighted an association between motor laterality and speech production laterality. It is thought that common demands for sequential processing may underlie this association. However, most studies in this area have relied on relatively small samples and have infrequently explored the reliability of the tools used to assess lateralization. We, therefore, established the validity and reliability of an online battery measuring sequence-based motor laterality and language laterality before exploring the associations between laterality indices on language and motor tasks. The online battery was completed by 621 participants, 52 of whom returned to complete the battery a second time. The three motor tasks included in the battery showed good between-session reliability (r ≥ .78) and were lateralized in concordance with hand preference. The novel measure of speech production laterality was left lateralized at population level as predicted, but reliability was less satisfactory (r = .62). We found no evidence of an association between sequence-based motor laterality and language laterality. Those with a left-hand preference were more strongly lateralized on motor tasks requiring midline crossing; this effect was not observed in right-handers. We conclude that there is little evidence of the co-lateralization of language and sequence-based motor skill on this battery.
Inconsistent language lateralisation - Testing the dissociable language laterality hypothesis using behaviour and lateralised cerebral blood flow.
BACKGROUND: Most people have strong left-brain lateralisation for language, with a minority showing right- or bilateral language representation. On some receptive language tasks, however, lateralisation appears to be reduced or absent. This contrasting pattern raises the question of whether and how language laterality may fractionate within individuals. Building on our prior work, we postulated (a) that there can be dissociations in lateralisation of different components of language, and (b) these would be more common in left-handers. A subsidiary hypothesis was that laterality indices will cluster according to two underlying factors corresponding to whether they involve generation of words or sentences, versus receptive language. METHODS: We tested these predictions in two stages: At Step 1 an online laterality battery (Dichotic listening, Rhyme Decision and Word Comprehension) was given to 621 individuals (56% left-handers); At Step 2, functional transcranial Doppler ultrasound (fTCD) was used with 230 of these individuals (51% left-handers). 108 left-handers and 101 right-handers gave useable data on a battery of three language generation and three receptive language tasks. RESULTS: Neither the online nor fTCD measures supported the notion of a single language laterality factor. In general, for both online and fTCD measures, tests of language generation were left-lateralised. In contrast, the receptive tasks were at best weakly left-lateralised or, in the case of Word Comprehension, slightly right-lateralised. The online measures were only weakly correlated, if at all, with fTCD measures. Most of the fTCD measures had split-half reliabilities of at least .7, and showed a distinctive pattern of intercorrelation, supporting a modified two-factor model in which Phonological Decision (generation) and Sentence Decision (reception) loaded on both factors. The same factor structure fitted data from left- and right-handers, but mean scores on the two factors were lower (less left-lateralised) in left-handers. CONCLUSIONS: There are at least two factors influencing language lateralization in individuals, but they do not correspond neatly to language generation and comprehension. Future fMRI studies could help clarify how far they reflect activity in specific brain regions.
Approaches to Measuring Language Lateralisation: An Exploratory Study Comparing Two fMRI Methods and Functional Transcranial Doppler Ultrasound.
In this exploratory study we compare and contrast two methods for deriving a laterality index (LI) from functional magnetic resonance imaging (fMRI) data: the weighted bootstrapped mean from the LI Toolbox (toolbox method), and a novel method that uses subtraction of activations from homologous regions in left and right hemispheres to give an array of difference scores (mirror method). Data came from 31 individuals who had been selected to include a high proportion of people with atypical laterality when tested with functional transcranial Doppler ultrasound (fTCD). On two tasks, word generation and semantic matching, the mirror method generally gave better agreement with fTCD laterality than the toolbox method, both for individual regions of interest, and for a large region corresponding to the middle cerebral artery. LI estimates from this method had much smaller confidence intervals (CIs) than those from the toolbox method; with the mirror method, most participants were reliably lateralised to left or right, whereas with the toolbox method, a higher proportion were categorised as bilateral (i.e., the CI for the LI spanned zero). Reasons for discrepancies between fMRI methods are discussed: one issue is that the toolbox method averages the LI across a wide range of thresholds. Furthermore, examination of task-related t-statistic maps from the two hemispheres showed that language lateralisation is evident in regions characterised by deactivation, and so key information may be lost by ignoring voxel activations below zero, as is done with conventional estimates of the LI.