Computer-Based Assessment: Dual-Task Outperforms Large-Screen Cancellation Task in Detecting Contralesional Omissions

Objective: Traditionally, asymmetric spatial processing (i.e., hemispatial neglect) has been assessed with paper-and-pencil tasks, but growing evidence indicates that computer-based methods are a more sensitive assessment modality. It is not known, however, whether simply converting well-established paper-and-pencil methods into a digital format is the best option. The aim of the present study was to compare sensitivity in detecting contralesional omissions of two different computer-based methods: a “digitally converted” cancellation task was compared with a computer-based Visual and Auditory dual-tasking approach, which has already proved to be very sensitive.Methods: Participants included 40 patients with chronic unilateral stroke in either the right hemisphere (RH patients, N = 20) or the left hemisphere (LH patients, N = 20) and 20 age-matched healthy controls. The cancellation task was implemented on a very large format (173 cm × 277 cm) or in a smaller (A4) paper-and-pencil version. The computer-based dual-tasks were implemented on a 15′′ monitor and required the detection of unilateral and bilateral briefly presented lateralized targets.Results: Neither version of the cancellation task was able to show spatial bias in RH patients. In contrast, in the Visual dual-task RH patients missed significantly more left-sided targets than controls in both unilateral and bilateral trials. They also missed significantly more left-sided than right-sided targets only in the bilateral trials of the Auditory dual-task.Conclusion: The dual-task setting outperforms the cancellation task approach even when the latter is implemented on a (large) screen. Attentionally demanding methods are useful for revealing mild forms of contralesional visuospatial deficits.

Stereoscopic Depth Perception and Visuospatial Dysfunction in Alzheimer’s Disease

With visuospatial dysfunction emerging as a potential marker that can detect Alzheimer’s disease (AD) even in its earliest stages and with disturbance in stereopsis suspected to be the prime contributor to visuospatial deficits in AD, we assessed stereoscopic abilities of patients with AD and mild cognitive impairment (MCI). Whereas previous research assessing patients’ stereoacuity has yielded mixed results, we assessed patients’ capacity to process coarse disparities that can convey adequate depth information about objects in the environment. We produced two virtual cubes at two different distances from the observer by manipulating disparity type (absolute vs. relative), disparity direction (crossed vs. uncrossed) and disparity magnitude, then had participants judge the object that appeared closer to them. Two patient groups performed as well as, or even better than elderly controls, suggesting that AD patients’ coarse disparity processing capacity is capable of supporting common tasks involving reaching, grasping, driving, and navigation. Results may help researchers narrow down the exact cause(s) of visuospatial deficits in AD and develop and validate measures to assess visuospatial dysfunction in clinical trials and disease diagnosis.

Differential associations of hypoxia, sleep fragmentation, and depressive symptoms with cognitive dysfunction in obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterized by recurrent episodes of partial or complete cessation of breathing during sleep and increased effort to breathe. This study examined patients who underwent overnight polysomnographic studies in a major sleep laboratory in Saudi Arabia. The study aimed to determine the extent to which intermittent hypoxia, sleep disruption, and depressive symptoms are independently associated with cognitive impairments in OSA. In the sample of 90 participants, 14 had no OSA, 30 mild OSA, 23 moderate OSA, and 23 severe OSA. The findings revealed that hypoxia and sleep fragmentation are independently associated with impairments of sustained attention and reaction time (RT). Sleep fragmentation, but not hypoxia, was independently associated with impairments in visuospatial deficits. Depressive symptoms were independently associated with impairments in the domains of sustained attention, RT, visuospatial ability, and semantic and episodic autobiographical memories. Since the depressive symptoms are independent of hypoxia and sleep fragmentation, effective reversal of cognitive impairment in OSA may require treatment interventions that target each of these factors.

Teaching Video NeuroImages: Posterior cortical atrophy presenting with Balint's syndrome

We present the case of a 68-year-old woman who developed progressive visuospatial deficits in a period of 18-month leading to the loss of her independence for activities of daily living. After examination, she showed signs of Balint's Syndrome with optic ataxia, oculomotor apraxia, and simultanagnosia without visual acuity impairment. After brain imaging showing severe bilateral parieto-occipital association cortex atrophy, a diagnosis of posterior cortical atrophy was made according to the 2017 International Consortium's criteria.

The spatiotemporal organization of episodic memory and its disruption in a neurodevelopmental disorder

Recent theories of episodic memory (EM) posit that the hippocampus provides a spatiotemporal framework necessary for representing events. If such theories hold true, then does the development of EM in children depend on the ability to first bind spatial and temporal information? And does this ability rely, at least in part, on normal hippocampal function? We investigated the development of EM in children 2–8 years of age (Study 1) and its impairment in Williams Syndrome, a genetic neurodevelopmental disorder characterized by visuospatial deficits and irregular hippocampal function, (Study 2) by implementing a nonverbal object-placement task that dissociates the what, where, and when components of EM. Consistent with the spatiotemporal-framework view of hippocampal EM, our results indicate that the binding of where and when in memory emerges earliest in development, around the age of 3, and is specifically impaired in WS. Space-time binding both preceded and was critical to full EM (what + where + when), and the successful association of objects to spatial locations seemed to mediate this developmental process.

Astrocytic Tau Deposition Is Frequent in Typical and Atypical Alzheimer Disease Presentations

Typical Alzheimer disease (AD) features an amnestic syndrome that reflects the progression of pathology through specific neural networks. However, a subset of patients exhibits atypical onset with prominent language, behavioral, or visuospatial deficits that are not explained by current neuropathological staging schemes. Astrogliopathy featuring tau inclusions with thorn-shaped and granular fuzzy morphologies is common in the aging brain and collectively known as aging-related tau astrogliopathy (ARTAG). Prior studies have identified tau-positive thorn-shaped astrocytes in the white matter that associate with a primary progressive aphasia phenotype in an AD cohort. However, a possible contribution of ARTAG copathology to AD clinical heterogeneity has yet to be systematically examined. To investigate whether ARTAG pathology contributes to atypical presentations, we mapped the presence and density of ARTAG subtypes throughout cortical and subcortical regions in a well-characterized cohort of AD cases enriched for atypical presentations. In our cohort, ARTAG pathology is frequent and correlates with older age and higher Braak stage. ARTAG subtypes exhibit distinct distribution patterns with subpial and subependymal deposition occurring in the amygdala, while white and grey matter astrocytic deposition are distributed throughout cortical regions. However, ARTAG pathology is equally prevalent in cases with typical and atypical clinical presentations.

Impairments of Visuospatial Attention in Children with Unilateral Spastic Cerebral Palsy

Aim. This observational study aimed at assessing the prevalence of visuospatial attention deficits in children with unilateral spastic cerebral palsy (USCP), taking into consideration the affected hemibody and the localization of the brain lesion. Method. Seventy-five children with USCP were assessed with four visuospatial attention tests: star cancellation, Ogden figure copy, line bisection, and proprioceptive pointing. Results. A majority (64%) of children with USCP presented a deficit in at least one test compared to the reference values. The alterations observed in children with left or right USCP were related to egocentric or allocentric neglect, respectively. Children with cortico/subcortical lesion presented more often visuospatial attention deficits than children with periventricular lesion. Visuospatial attention deficits were not associated with brain lesion locations. Interpretation. Visuospatial attention deficits are prevalent in children with USCP and should be taken into account during their rehabilitation process. The present results shed new light on the interpretation of motor impairments in children with USCP as they may be influenced by the frequent presence of visuospatial deficits.

Atypical presentations of Alzheimer’s disease

Alzheimer’s disease usually presents in older age with progressive episodic memory loss. Atypical presentations of Alzheimer’s disease occur and involve non-amnestic and early-onset forms of the disease. Posterior cortical atrophy (PCA) and logopenic progressive aphasia (lvPPA) are two well-described syndromes that are most commonly due to atypical presentations of Alzheimer’s disease. PCA is a higher-order disturbance of vision whilst lvPPA is characterized by hesitant speech with word-finding difficulties and problems with repetition of words and phrases. Early-onset Alzheimer’s disease presents before the age of 65 and typically consists of a constellation of progressive cortical deficits including language disturbance, apraxia, visuospatial deficits, and poor working memory. Alzheimer’s disease may rarely be inherited because of an autosomal dominant mutation in one of three genes (PSEN1, PSEN2, and APP). Recognition and accurate diagnosis of these atypical forms is vital to ensure patients receive the most appropriate care and treatment.