Cognitive bias induced by visuo-motor adaptation to prisms: a simulation of unilateral neglect in normal individuals?

Unilateral neglect has been recently shown to be improved following a short period of adaptation to wedge prisms. The present study investigates whether visuo-motor adaptation can generate a bias in normals on line bisection tasks classically used to assess unilateral neglect. Our results show that adaptation to left-deviating prisms induces a stronger rightward bias for the perceptual than the motor line bisection task. This bias is in the same direction as the one observed in unilateral neglect. No significant effect is produced by adaptation to right-deviating prisms. Our data confirm that the plasticity of inter-sensory and sensori-motor coordinations affects higher levels of space representation. These asymmetric results may reflect the inherent bias of the brain's structural organisation and provide an empirical explanation for the left-sided predominance of unilateral neglect.     

Is macrocephaly a neural marker of a local bias in autism?

Previous research has suggested that the local processing bias often reported in studies of Autism Spectrum Condition may only be typical of a subgroup of individuals with autism also presenting with macrocephaly. The current study examined a group of children with autism, with and without macrocephaly, on the Children's Embedded Figures Test (CEFT), a well-established measure of local processing bias. The results demonstrated that the children with autism and macrocephaly performed significantly better on the CEFT than children with autism without macrocephaly, indicative of a local bias. These results lend support to the proposal that both macrocephaly in autism and a local processing bias may arise from the same underlying neural processes and these characteristics represent an endophenotype in a subgroup of individuals with ASC worthy of further investigation.     

The overestimation of performance: a specific bias of aging?

The decline of postural abilities with age leads to increased falls. In this study, we suggest that a disturbance in the perception of postural affordances, characterized by an overestimation of performance, could be a major risk of falls specifically in the elderly. In addition, we test the possible link between the overestimation of capabilities and postural balance as we know degraded in the elderly. A group of 10 young subjects (M = 24.2 years ± 2.04) and a group of 10 elderly subjects (M = 75.9 years ± 5.7) must evaluate, without action, the maximum height of an obstacle that they can stride over. Then their postural performances are measured. The results show that, contrary to young people who correctly evaluate their performance (difference of 1.75 cm between estimated performance and real performance), older participants overestimate their maximum height of crossing over (12.5 cm difference between performance and estimated real performance). Moreover, the overestimation of performance is associated with poor postural stability. The bias of overestimation may stem from a lack of updating of motor programs caused by a functional brain change with age and/or lack of exercise who reduces updating by trial and error.     

Is there a distortion of body projection in extracorporeal space in neglect patients?

Neglect patients often present with a rightward shift of the direction straight-ahead of body midline. We investigated whether directions ahead of other body parts were similarly shifted or were differentially affected. Right brain-damaged patients, with and without neglect, and normal subjects had to indicate by manual pointings, the directions straight-ahead of the navel, the nose, the left and right shoulders. In neglect patients, constant errors varied across directions with a decrease in magnitude from left to right, suggesting a compression of body projection in extracorporeal space. Moreover, the projection of the left hemibody was smaller than the right in all subjects, with and without neglect. This unexpected finding is discussed with regard to other spatial asymmetries observed in normal subjects.     

The role of acetylcholine in negative encoding bias: Too much of a good thing?

Optimal acetylcholine (ACh) signaling is important for sustained attention and facilitates learning and memory. At the same time, human and animal studies have demonstrated increased levels of ACh in the brain during depressive episodes and increased symptoms of anxiety, depression, and reactivity to stress when ACh breakdown is impaired. While it is possible that the neuromodulatory roles of ACh in cognitive and affective processes are distinct, one possibility is that homeostatic levels of ACh signaling are necessary for appropriate learning, but overly high levels of cholinergic signaling promote encoding of stressful events, leading to the negative encoding bias that is a core symptom of depression. In this review, we outline this hypothesis and suggest potential neural pathways and underlying mechanisms that may support a role for ACh signaling in negative encoding bias.     

Chimeric faces, visual field bias, and reaction time bias: have we been missing a trick?

The chimeric faces test is a frequently used behavioural test of lateralisation for cognitive processing. Performance on this task is typically quantified in terms of bias towards selecting faces where positive facial emotion is expressed in the viewer's left visual field, indicating right hemisphere dominance for the task. This paper examines an alternative measure that may be extracted from responses to the chimeric faces test: reaction time bias. There was a strong positive correlation between the two asymmetry measures, which remained even after controlling for sex and handedness. The possible uses of reaction time bias in the measurement of cerebral lateralisation are discussed.     

Chimeric faces,visual field bias,and reaction time bias: Have we been missing a trick?

The chimeric faces test is a frequently used behavioural test of lateralisation for cognitive processing. Performance on this task is typically quantified in terms of bias towards selecting faces where positive facial emotion is expressed in the viewer's left visual field, indicating right hemisphere dominance for the task. This paper examines an alternative measure that may be extracted from responses to the chimeric faces test: reaction time bias. There was a strong positive correlation between the two asymmetry measures, which remained even after controlling for sex and handedness. The possible uses of reaction time bias in the measurement of cerebral lateralisation are discussed.     

Shifting effects in randomised controlled trials of complex interventions: a new kind of performance bias?

Gold C, Erkkilä J, Crawford MJ. Shifting effects in randomised controlled trials of complex interventions: a new kind of performance bias? Objective: Randomised controlled trials (RCTs) aim to provide unbiased estimates of treatment effects. However, the process of implementing trial procedures may have an impact on the performance of complex interventions that rely strongly on the intuition and confidence of therapists. We aimed to examine whether shifting effects over the recruitment period can be observed that might indicate such impact. Method: Three RCTs investigating music therapy vs. standard care were included. The intervention was performed by experienced therapists and based on established methods. We examined outcomes of participants graphically, analysed cumulative effects and tested for differences between first vs. later participants. We tested for potential confounding population shifts through multiple regression models. Results: Cumulative differences suggested trends over the recruitment period. Effect sizes tended to be less favourable among the first participants than later participants. In one study, effects even changed direction. Age, gender and baseline severity did not account for these shifting effects. Conclusion: Some trials of complex interventions have shifting effects over the recruitment period that cannot be explained by therapist experience or shifting demographics. Replication and further research should aim to find out which interventions and trial designs are most vulnerable to this new kind of performance bias.     

Rotation or translation of auditory space in neglect? A case study of chronic right-sided neglect

Egocentric models of neglect explain the lateralised omission of stimuli in neglect patients by an ipsilesional shift of a subjective reference frame. However, they differ in the direction of shift (rotation around the midsagittal plane versus translation in front/back space). We tested this hypothesis in a patient (AJ) with persistent right-sided neglect following a left temporo-parieto-occipital and hypoxic lesion and in six age-matched healthy subjects. AJ showed visual neglect in line bisection, size matching, reading and visual search. Auditory localization was tested by using two different psychophysical techniques based on binaurally simulated stimuli for the horizontal plane in front and back space. Eye position was continuously monitored during stimulus presentation in all subjects. AJ revealed a significant ipsilesional, leftward shift of his auditory subjective median plane (ASMP) in front space (mean: -22.6 degrees), and a rightward shift of the ASMP in back space (+14.5 degrees). This pattern of results was replicated with a different psychophysical technique in a retest 10 months later. The rotational shift of AJ's ASMP contrasted with normal performance in the healthy subjects. Monaural hearing deficits can not account for these differential findings as all subjects (including AJ) performed normally. In conclusion, a rotation of the egocentric spatial reference frame may occur in the auditory modality for right-sided neglect.     

Peer support working: a question of ontology and epistemology?

There is increasing attention to the impacts of stigma and discrimination related to mental health on quality of life and access to and quality of healthcare. Effective strategies for stigma reduction exist, but most evidence comes from high-income settings. Recent reviews of stigma research have identified gaps in the field, including limited cultural and contextual adaptation of interventions, a lack of contextual psychometric information on evaluation tools, and, most notably, a lack of multi-level strategies for stigma reduction. The Indigo Partnership research programme will address these knowledge gaps through a multi-country, multi-site collaboration for anti-stigma interventions in low- and middle-income countries (LMICs) (China, Ethiopia, India, Nepal, and Tunisia). The Indigo Partnership aims to: (1) carry out research to strengthen the understanding of mechanisms of stigma processes and reduce stigma and discrimination against people with mental health conditions in LMICs; and (2) establish a strong collaborative research consortium through the conduct of this programme. Specifically, the Indigo Partnership involves developing and pilot testing anti-stigma interventions at the community, primary care, and mental health specialist care levels, with a systematic approach to cultural and contextual adaptation across the sites. This work also involves transcultural translation and adaptation of stigma and discrimination measurement tools. The Indigo Partnership operates with the key principle of partnering with people with lived experience of mental health conditions for the development and implementation of the pilot interventions, as well as capacity building and cross-site learning to actively develop a more globally representative and equitable mental health research community. This work is envisioned to have a long-lasting impact, both in terms of the capacity building provided to participating institutions and researchers, and the foundation it provides for future research to extend the evidence base of what works to reduce and ultimately end stigma and discrimination in mental health.     

Is preattentive bias predictive of autonomic reactivity in response to a stressor?

Biased processing of threatening information may play a casual role in the development of anxiety disorders. Even though empirical evidence points to the fact that preattentive bias can predict subjectively experienced distress in response to a stressor, it is still unknown whether it could be useful in predicting the physiological reactivity in response to a stressor. In the present study, the emotional Stroop task was used to measure preattentive bias. Whereas Stroop interference for masked threat words (i.e., preattentive bias) was found to be positively associated with emotional distress (self-reported) in response to a laboratory stressor, this association was reversed when the autonomic reactivity (electrodermal activity) was used as a measure of emotional response to the very same stressor. Also, neither of these effects were a function of pre-existing anxiety levels. The negative association between preattentive bias and autonomic reactivity corresponds to the autonomic inflexibility seen in clinical anxiety (or very high scores of trait anxiety) when exposed to stressful events. Results were discussed in terms of an inability to automatically inhibit the processing of threatening cues that seems to be a vulnerability marker for anxiety.     

To be or not to be: a question of B-Raf?

A recent study has identified the B-Raf gene as essential for the survival of explanted sensory and motor neurons in culture in response to neurotrophic factors. This finding sheds new light on the control of neuronal development and poses new questions with regard to Raf-isozyme-specific functions.     

The anatomy of neglect without hemianopia: a key role for parietal-frontal disconnection?

We investigated the anatomical correlates of chronic unilateral neglect in right brain damaged patients with no visual field defects. Independently from basal ganglia or thalamus involvement, neglect patients had a subcortical area of maximal lesion overlap (maxov) in the superior longitudinal fasciculus (SLF). Neglect patients without lesion of subcortical nuclei had an additional maxov area in the rostralmost limit of the supramarginal gyrus (SmG). Patients without neglect showed a maxov area in the corticospinal tract with no involvement of the SLF or SmG. These findings call attention to the role of parietal-frontal disconnection in the pathogenesis of neglect. This disconnection can make neglect generalised and enduring also in patients suffering only partial damage of the parietal-temporal cortex, and who would otherwise show more selective attentional impairments.     

Is tau aggregation toxic or protective: a sensible question in the absence of sensitive methods?

In Alzheimer's disease brain, the microtubule-associated protein tau detaches from the microtubules, pathologically interacts with cellular proteins, and eventually forms insoluble aggregates that also bind and trap a myriad of proteins. As these proteins are depleted from the cellular pool, they are unavailable for physiological functions. Thus elevated tau levels are pathogenic, even in the absence of tau aggregation. Whereas it is reasonable to assume that tau aggregation is toxic during late stages of disease, the question arises whether early in disease it may be protective. This question can be addressed in tau transgenic animal models in which tau aggregation has been correlated with behavioral impairment. We discuss ways of how tau aggregation is monitored in these mice and what the detection limits are of these methods. We conclude that new tools are needed to measure the different stages of tau aggregation.