Attentional impairments in Huntington's disease: A specific deficit for the executive conflict

Attentional networks in co-occurring generalized anxiety disorder and major depression disorder: Towards a staging approach to the executive control deficits

INTRODUCTION

Major Depression Disorder (MDD) and Generalized Anxiety Disorder (GAD) often co-occur, but the neurocognitive mechanisms of this co-occurrence remain unknown. Prominent views have pointed to attentional processes as potent mechanisms at play in MDD and GAD, respectively. Yet uncertainty remains regarding the very nature of attentional impairments in patients with co-occurring MDD and GAD.

METHODS

Inspired by contemporary models of attentional networks, we compared the three main attentional networks, namely the orienting, alerting, and executive networks of the Attention Network Task's model, in four groups of patients with, respectively, co-occurring DSM-5 MDD and GAD (n = 30), DSM-5 MDD only (n = 30), DSM-5 GAD only (n = 30), or free from any DSM-5 diagnosis (n = 30). To capture the multivariate nature of our data, we examined between-group differences in the attentional networks through a multivariate analysis of variance.

RESULTS

Patients with co-occurring MDD and GAD exhibited more severe impairments in the executive control network than those with only one of the disorders. Although patients with MDD or GAD solely did not differ in terms of attentional impairments, both groups showed significantly more impairments in the executive control network than those free from any DSM-5 diagnosis (all Bonferonni-corrected post-hoc ps < 0.05).

CONCLUSIONS

Our findings align with a longstanding staging approach to comorbidity whereby, via synergistic effects, co-occurring disorders produce more damages than the sum of each disorder. Here, for the first time, we extended this approach to the executive network of attention in the context of the co-occurrence between MDD and GAD.

Cognitive and social cognition deficits in Huntington's disease differ between the prodromal and the manifest stages of the condition: A scoping review of recent evidence

OBJECTIVE

Huntington's disease (HD) is a dramatic neurodegenerative disorder encompassing severe motor symptoms coupled to significant cognitive and social cognition deficits. However, it is not clear whether and how patients' neuropsychological profile changes between the prodromal and the manifest stages of the condition. The aim of the present in-depth review is to consider cognitive and social cognition impairment in HD patients by differentiating deficits arising before diagnosis from those evident from the manifest phase onwards.

METHODS

Electronic databases were searched between January 1^st , 2010 and December 31^st , 2020 by using multiple combinations of keywords related to the investigation of neuropsychological profile in HD for preliminary search, and by defining strict selection criteria for studies to be included.

RESULTS

Forty-two studies were included. Evidence suggests that the neuropsychological profile in HD reflects a complex pathological spectrum of deficits. It includes impairment in the realms of executive functions, memory, attention, information processing, and social cognition. Interestingly, patients' profiles differ significantly between the manifest and the prodromal stages of their condition, not only in quantitative terms but also from a qualitative point of view.

CONCLUSIONS

Researchers and clinicians should thus include in clinical routine timely and specific neuropsychological assessments in order to monitor patients' cognitive status as time goes by, with the ultimate goal to implement effective clinical management strategies.

PRACTITIONER POINTS

The neuropsychological profile in HD encompasses a complex pathological spectrum of deficits. Patients' profiles differ significantly between the manifest and the prodromal stages of their condition. Clinicians should include in everyday practice a timely and specific neuropsychological assessment. Detecting patients' cognitive status during the early stages of the condition already can contribute significantly to implement effective clinical management strategies.

Approach to Posture and Gait in Huntington's Disease

Disturbances of gait occur in all stages of Huntington’s disease (HD) including the premanifest and prodromal stages. Individuals with HD demonstrate the slower speed of gait, shorter stride length, and increased variability of gait parameters as compared to controls; cognitive disturbances in HD often compound these differences. Abnormalities of gait and recurrent falls lead to decreased quality of life for individuals with HD throughout the disease. This scoping review aims to outline the cross-disciplinary approach to gait evaluation in HD and will highlight the utility of objective measures in defining gait abnormalities in this patient population.

Brain compensation during response inhibition in premanifest Huntington's disease

Premanifest Huntington's disease (pre-HD) individuals typically show increased task-related functional magnetic resonance imaging (fMRI), suggested to reflect compensatory strategies. Despite the evidence, no study has attempted to understand the compensatory process in light of 'formal' models of compensation. We used a quantitative model of compensation - the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH), to characterise compensation in pre-HD using fMRI. Pre-HD individuals (n = 15) and controls (n = 15) performed a modified stop-signal task that incremented in four levels of stop difficulty. Our results did not support the critical assumption of the CRUNCH model - controls did not show increased fMRI activity with increased level of stop difficulty; however, controls showed decreased fMRI activity with increased stop difficulty in right inferior frontal gyrus and right caudate nucleus. Relative to controls, pre-HD individuals showed increased fMRI activity in right inferior frontal gyrus and in right caudate nucleus at higher levels of stop difficulty, which is the opposite effect to that predicted by the model. Our findings suggest a compensatory process of the response inhibition network in pre-HD; however, the pattern of fMRI activity was not in the manner expected by CRUNCH.

β-lactolin, a whey-derived glycine-threonine-tryptophan-tyrosine lactotetrapeptide, improves prefrontal cortex-associated reversal learning in mice

Dementia and cognitive decline have become worldwide public health problems. We have previously reported that a whey-derived glycine-threonine-tryptophan-tyrosine peptide, β-lactolin, improves hippocampus-dependent memory functions in mice. The supplementation with a whey digest rich in β-lactolin improves memory retrieval and executive function in a clinical trial, but the effect of β-lactolin on prefrontal cortex (PFC)-associated cognitive function was unclear. Here we examined the effect of β-lactolin and the whey digest on PFC-associated visual discrimination (VD) and reversal discrimination (RD) learning, using a rodent touch panel-based operant system. β-Lactolin and the whey digest significantly improved the RD learning, and the whey digest enhanced the response latency during the VD task, indicating that β-lactolin and the whey digest improve PFC-associated cognitive functions. Given the translational advantages of the touch panel operant system, consumption of β-lactolin in daily life could be beneficial for improving human PFC-associated cognitive function, helping to prevent dementia.

The effects of dual-task cognitive interference on gait and turning in Huntington's disease

Huntington’s disease (HD) is characterized by motor, cognitive, and psychiatric dysfunction. HD progression causes loss of automaticity, such that previously automatic tasks require greater attentional resources. Dual-task (DT) paradigms and fast-paced gait may stress the locomotor system, revealing deficits not seen under single-task (ST). However, the impact of gait “stress tests” on HD individuals needs further investigation. Therefore, the aims of this study were to investigate whether: 1) fast-paced and dual-task walking uncover deficits in gait and turning not seen under single-task, 2) cognitive and gait outcomes relate to fall incidence, and 3) gait deficits measured with wearable inertial sensors correlate with motor symptom severity in HD as measured by the Unified Huntington’s disease Rating Scale-total motor score (UHDRS-TMS). Seventeen HD (55 ± 9.7 years) and 17 age-matched controls (56.5 ± 9.3 years) underwent quantitative gait testing via a 25m, two-minute walk test with APDM^TM inertial sensors. Gait was assessed under a 1) ST, self-selected pace, 2) fast-as-possible (FAP) pace, and 3) verbal fluency DT. The UHDRS-TMS and a cognitive test battery were administered, and a retrospective fall history was obtained. During ST, DT, and FAP conditions, HD participants demonstrated slower gait, shorter stride length, and greater lateral step and stride length variability compared to controls (p<0.00001 to 0.034). Significant dual-task costs (DTC) were observed for turns; HD participants took more time (p = 0.013) and steps (p = 0.028) to complete a turn under DT compared to controls. Higher UHDRS-TMS correlated with greater stride length variability, less double-support, and more swing-phase time under all conditions. Decreased processing speed was associated with increased gait variability under ST and FAP conditions. Unexpectedly, participant’s self-reported falls did not correlate with any gait or turn parameters. HD participants demonstrated significantly greater DTC for turning, which is less automatic than straight walking, requiring coordination of body segments, anticipatory control, and cortical regulation. Turn complexity likely makes it more susceptible to cognitive interference in HD.

Unfolding the Complex Dynamic Interplay Between Attentional Processes and Anxiety: A Commentary on Ghassemzadeh, Rothbart, and Posner

Theories about the involvement of attention in feelings of fear and anxiety have been debated in philosophical circles since long before the foundation of experimental psychology and cognitive neuroscience. In this issue, Ghassemzadeh, Rothbart, and Posner (2019) provide a much-needed historical and conceptual review of the relations between attention and anxiety disorders. Throughout their paper, they argue that insights from the study of brain networks of attention offer a particularly viable prospect for best clarifying the complex relations between attentional processes and anxiety. We fully share this view. Moreover, we believe that the computational and conceptual tools of network analysis (also known as graph theory) can enable researchers to move even closer to elucidating the complex dynamic interplay between those phenomena. In this commentary, we explain why and how to use network analysis for this purpose.

The Effects of Dual-Task Cognitive Interference and Environmental Challenges on Balance in Huntington's Disease

BACKGROUND

Huntington's disease (HD) is characterized by chorea, balance and gait impairments, and cognitive deficits, which increase fall risk. Dual task (DT) and environmentally challenging paradigms reflect balance related to everyday life. Furthermore, the impact of cognitive deficits on balance dysfunction and falls in HD is unknown.

OBJECTIVE

To determine the impact of DT interference, sensory feedback, and cognitive performance on balance and falls in HD.

METHODS

Seventeen participants with HD (55 ± 9.7 years) and 17 age-matched controls (56.5 ± 9.3 years) underwent quantitative balance testing with APDM inertial sensors. Postural sway was assessed during conditions of manipulated stance, vision, proprioception, and cognitive demand. The DT was a concurrent verbal fluency task. Neuropsychological assessments testing multiple cognitive domains were also administered.

RESULTS

HD participants exhibited significantly greater total sway area, jerk, and variability under single-task (ST) and DT conditions compared to controls (P = 0.0002 - < 0.0001). They also demonstrated greater DT interference with vision removed for total sway area (P = 0.01) and variability (P = 0.02). Significantly worse postural control was observed in HD with vision removed and reduced proprioception (P = 0.001 - 0.01). Decreased visuospatial performance correlated with greater total sway and jerk (P = 0.01; 0.009). No balance parameters correlated with retrospective falls in HD.

CONCLUSIONS

HD participants have worse postural control under DT, limited proprioception/vision, and greater DT interference with a narrowed base and no visual input. These findings may have implications for designing motor and cognitive strategies to improve balance in HD.

Does Change in Attention Control Mediate the Impact of tDCS on Attentional Bias for Threat? Limited Evidence from a Double-blind Sham-controlled Experiment in an Unselected Sample

Neurocognitive models of attentional bias for threat posit that attentional bias may result from a decreased activation of the left prefrontal cortex, and especially of its dorsolateral part (dlPFC), resulting in an impaired attention control. Consequently, a transient increase of neural activity within the left dlPFC via non-invasive brain stimulation reduces attentional bias among both anxious and nonanxious participants. Yet, it is still unclear whether the impact of dlPFC activation on attentional bias is mediated by improvement in attention control. In this experiment, we sought to test this hypothesis in an unselected sample (n = 20). Accordingly, we adopted a double-blind within-subject protocol in which we delivered a single-session of anodal versus sham transcranial Direct Current Stimulation (tDCS) over the left dlPFC during the completion of a task assessing attention control. We also assessed its subsequent impact on attentional bias. Neither attention control nor attentional bias did significantly improve following anodal tDCS. Although our results do not support our main hypothesis, we believe the present null results to be particularly useful for future meta-research in the field. We also formulated a series of methodological recommendations for future research aiming at testing the tDCS-induced modification of attentional bias.