Visuospatial Processing Research Articles

Visuospatial processing can be disrupted in healthcare workers during the COVID-19 pandemic

Visuospatial processing can be disrupted in healthcare workers during the COVID-19 pandemic

Demographic, clinical, biomarker, and neuropathological correlates of posterior cortical atrophy: an international cohort study and individual participant data meta-analysis

Posterior cortical atrophy is a rare syndrome characterised by early, prominent, and progressive impairment in visuoperceptual and visuospatial processing. The disorder has been associated with underlying neuropathological features of Alzheimer's disease, but large-scale biomarker and neuropathological studies are scarce. We aimed to describe demographic, clinical, biomarker, and neuropathological correlates of posterior cortical atrophy in a large international cohort. We searched PubMed between database inception and Aug 1, 2021, for all published research studies on posterior cortical atrophy and related terms. We identified research centres from these studies and requested deidentified, individual participant data (published and unpublished) that had been obtained at the first diagnostic visit from the corresponding authors of the studies or heads of the research centres. Inclusion criteria were a clinical diagnosis of posterior cortical atrophy as defined by the local centre and availability of Alzheimer's disease biomarkers (PET or CSF), or a diagnosis made at autopsy. Not all individuals with posterior cortical atrophy fulfilled consensus criteria, being diagnosed using centre-specific procedures or before development of consensus criteria. We obtained demographic, clinical, biofluid, neuroimaging, and neuropathological data. Mean values for continuous variables were combined using the inverse variance meta-analysis method; only research centres with more than one participant for a variable were included. Pooled proportions were calculated for binary variables using a restricted maximum likelihood model. Heterogeneity was quantified using I2. We identified 55 research centres from 1353 papers, with 29 centres responding to our request. An additional seven centres were recruited by advertising via the Alzheimer's Association. We obtained data for 1092 individuals who were evaluated at 36 research centres in 16 countries, the other sites having not responded to our initial invitation to participate to the study. Mean age at symptom onset was 59·4 years (95% CI 58·9-59·8; I2=77%), 60% (56-64; I2=35%) were women, and 80% (72-89; I2=98%) presented with posterior cortical atrophy pure syndrome. Amyloid β in CSF (536 participants from 28 centres) was positive in 81% (95% CI 75-87; I2=78%), whereas phosphorylated tau in CSF (503 participants from 29 centres) was positive in 65% (56-75; I2=87%). Amyloid-PET (299 participants from 24 centres) was positive in 94% (95% CI 90-97; I2=15%), whereas tau-PET (170 participants from 13 centres) was positive in 97% (93-100; I2=12%). At autopsy (145 participants from 13 centres), the most frequent neuropathological diagnosis was Alzheimer's disease (94%, 95% CI 90-97; I2=0%), with common co-pathologies of cerebral amyloid angiopathy (71%, 54-88; I2=89%), Lewy body disease (44%, 25-62; I2=77%), and cerebrovascular injury (42%, 24-60; I2=88%). These data indicate that posterior cortical atrophy typically presents as a pure, young-onset dementia syndrome that is highly specific for underlying Alzheimer's disease pathology. Further work is needed to understand what drives cognitive vulnerability and progression rates by investigating the contribution of sex, genetics, premorbid cognitive strengths and weaknesses, and brain network integrity. None.

Simulating Local Biases in Visual Attention in Neurocognitive Performance.

Typical visual perception includes an attention bias toward right hemisphere mediated global, holistic cortical processing. An atypically local, detail-oriented focus of attention is characteristic of left hemisphere processing and is often observed in patients whose field of attention is restricted by certain types of neurocognitive impairment. We designed the present pair of studies to induce a local attentional focus to observe its consequences on neurocognitive measures of visuospatial processing. In Experiment I, participants wore glasses mimicking simultanagnosia, a disorder of visual attention, to induce a narrowed, atypical attentional style while they completed visual neuropsychological tasks. This simulation impaired participants' capacities to visually synthesize and efficiently reproduce Complex Figure stimuli as measured with the Boston Qualitative Scoring System (BQSS), and it induced an atypical attentional style on Rorschach Performance Assessment System (R-PAS) responses. In Experiment II, participants wore glasses designed to provoke differential hemispheric activation, also hypothesized to influence style of visual attention; but this manipulation did not influence neurocognitive task performance. We discuss implications for the interpretation of BQSS and R-PAS scores and offer directions for future research.

Resources for reasoning of chemistry concepts: multimodal molecular geometry

Central to conceptual understanding of STEM disciplines is visuospatial processing. Despite its acknowledged role in assuring learners’ success, less is known about the underlying reasoning students must employ when solving 3-D problems and the ways in which gaining an understanding of this can inform formative assessment and learning in STEM education. Chemists must utilise their spatial understanding when visualising 3-D structures and processes from 2-D representations and so this exploratory practitioner-researcher study sought to identify the ways in which secondary school chemistry students reason when explaining their predictions about molecular geometry, and how the use of certain modalities was linked to assessed accuracy. Coding of students’ verbal and written responses to the research task revealed that students employed multiple reasoning strategies and conceptual resources to facilitate use of analytical heuristics and imagistic reasoning. Analysis of students’ verbal responses and spontaneous gestures provided insight into the extent of imagistic vs. analytical reasoning and the finer-grained conditions which promoted their use. Importantly, it was observed that despite being instructed on the use of VSEPR theory to find analytical solutions, some students exhibited preference for alternative reasoning strategies drawing upon imagistic reasoning; showing more nuanced and varying degrees of accuracy through their verbal responses and representations gestured in 3D space. This work has pedagogical implications as use of specific reasoning strategies and the identification of key conceptual resources is not readily promoted as classroom practice for learning or assessment. This study therefore raises questions and contributes to the evidence base for attending to learners’ visuospatial thinking, as revealed through the multiple modalities they may use to assist and communicate their understanding, and highlights the significance of this to formative assessment in Chemistry and STEM Education.

"Picture this from there": spatial perspective-taking in developmental visuospatial disorder and developmental coordination disorder.

Either Developmental Visuospatial Disorder (DVSD) and Developmental Coordination Disorder (DCD) present with difficulties in visuospatial processing, even though entailing different degrees of impairment. Among the visuospatial domain, spatial perspective taking is essential to interact with the environment and is significantly involved in many daily activities (e.g., environment navigation and spatial orienting). Notwithstanding, no previous studies have investigated this spatial domain in children with DVSD and limited evidence is available regarding DCD. Consistent with a transdiagnostic approach, the first goal of the present study was to compare spatial perspective taking abilities of these groups, also including a control group of not diagnosed peers (ND). Secondly, the role of different fine-motor and visuo-spatial predictors on the spatial perspective taking performance was considered. A total of 85 participants (DVSD = 26; DCD = 26; ND = 33), aged between 8 and 16 years old, were included in the study. Tasks assessing spatial perspective taking, fine-motor, visual imagery, and mental rotation skills, as well as visuo-spatial working memory were administered. Overall, our results confirmed weaknesses in spatial perspective taking in both clinical groups, with the DVSD obtaining the lowest scores. Similarities and differences in the predictors accounting for the performance in the spatial perspective taking task emerged, suggesting the possible employment of different fine-motor or visuospatial strategies by group. Findings are discussed considering the potential impact they may have both in research and clinical practice.

Computational thinking in university students: The role of fluid intelligence and visuospatial ability.

Computational thinking (CT) is a set of problem-solving skills with high relevance in education and work contexts. The present paper explores the role of key cognitive factors underlying CT performance in non-programming university students. We collected data from 97 non-programming adults in higher education in a supervised setting. Fluid intelligence, crystallized intelligence, and visuospatial ability were assessed using computerized adaptive tests; CT was measured using the Computational Thinking test. The direct and indirect effects of gender and visuospatial ability through fluid intelligence on CT were tested in a serial multiple mediator model. Fluid intelligence predicted CT when controlling for the effects of gender, age, and visuospatial ability, while crystallized intelligence did not predict CT. Men had a small advantage in CT performance when holding the effects of cognitive abilities constant. Despite its large correlation with gender and CT, visuospatial ability did not directly influence CT performance. Overall, we found that programming-naive computational thinkers draw on their reasoning ability that does not rely on previously acquired knowledge to solve CT problems. Visuospatial ability and CT were spuriously associated. Drawing on the process overlap theory we propose that tests of fluid intelligence and CT sample an overlapping set of underlying visuospatial processes.

The effects of a therapeutic program based on motor learning in the recovery of apraxia of speech in children

The purpose of the present study is to analyze comparatively the effects of some therapeutic interventions to improve the symptoms of apraxia of speech in children (CAS). In this sense, three different therapeutic programs were implemented, each lasting 12 months, in three groups of children. Two measurements were made, before and after the children's participation in the programs. P1 included therapy based on augmentative and alternative communication, P2 included therapy based on the classic speech therapy model and therapeutic speech massage, P3 included therapy based on verbal motor learning, VML. 106 children diagnosed with CAS participated in the study, aged between 5 and 7 years, M = 5.75, SD = .75, of which 81 boys (76%) and 25 girls (24%), were randomly divided into three groups. CAS severity was measured using a grid from the Dynamic Assessment of Motor Speech Skills, measuring articulatory accuracy, vowel scoring, and prosody. Visuomotor accuracy, visuospatial processing, phonemic hearing, narrative memory, and attention were measured with a series of tests from the PEDb and PEDa packages (Cognitrom, 2012). Although all three therapeutic programs registered significant effects on the improvement of CAS symptomatology, the most notable effects were obtained by the VML method. The practical implications of the study are discussed, as well as future research directions.

Acute hypoxia alters visuospatial attention orienting: an electrical neuroimaging study

Our study investigated the effects of hypoxia on visuospatial attention processing during preparation for a single/double-choice motor response. ERPs were recorded in two sessions in which participants breathed either ambient-air or oxygen-impoverished air. During each session, participants performed four cue-target attention orienting and/or alerting tasks. Replicating the classic findings of valid visuospatial attentional orienting modulation, ERPs to pre-target cues elicited both an Anterior directing attention negativity (ADAN)/CNV and a posterior Late directing attention positivity (LDAP)/TP, which in ambient air were larger for attention orienting than for alerting. Hypoxia increased the amplitude of both these potentials in the spatial orienting conditions for the upper visual hemifield, while, for the lower hemifield, it increased ADAN/CNV, but decreased LDAP/TP for the same attention conditions. To these ERP changes corresponded compensatory enhanced activation of right anterior cingulate cortex, left superior parietal lobule and frontal gyrus, as well as detrimental effects of hypoxia on behavioral overt performance. Together, these findings reveal for the first time, to our knowledge, that (1) these reversed alterations of the activation patterns during the time between cue and target occur at a larger extent in hypoxia than in air, and (2) acute normobaric hypoxia alters visuospatial attention orienting shifting in space.

Subcortical functional connectivity and its association with walking performance following deployment related mild TBI.

The relation between traumatic brain injury (TBI), its acute and chronic symptoms, and the potential for remote neurodegenerative disease is a priority for military research. Structural and functional connectivity (FC) of the basal ganglia, involved in motor tasks such as walking, are altered in some samples of Service Members and Veterans with TBI, but any behavioral implications are unclear and could further depend on the context in which the TBI occurred. In this study, FC from caudate and pallidum seeds was measured in Service Members and Veterans with a history of mild TBI that occurred during combat deployment, Service Members and Veterans whose mild TBI occurred outside of deployment, and Service Members and Veterans who had no lifetime history of TBI. FC patterns differed for the two contextual types of mild TBI. Service Members and Veterans with deployment-related mild TBI demonstrated increased FC between the right caudate and lateral occipital regions relative to both the non-deployment mild TBI and TBI-negative groups. When evaluating the association between FC from the caudate and gait, the non-deployment mild TBI group showed a significant positive relationship between walking time and FC with the frontal pole, implicated in navigational planning, whereas the deployment-related mild TBI group trended towards a greater negative association between walking time and FC within the occipital lobes, associated with visuo-spatial processing during navigation. These findings have implications for elucidating subtle motor disruption in Service Members and Veterans with deployment-related mild TBI. Possible implications for future walking performance are discussed.

Brain Active Areas Associated with a Mental Arithmetic Task: An eLORETA Study.

The neural underpinnings of mental calculation, the fundamentals of arithmetic representations and processes, and the development of arithmetic abilities have been explored by researchers over the years. In the present work, we report a study that analyzes the brain-activated areas of a group of 35 healthy subjects (9 males, 26 females, mean age ± SD = 18.23 ± 2.20 years) who performed a serial subtraction arithmetic task. In contrast to most of the studies in the literature based on fMRI, we performed the brain active source reconstruction starting from EEG signals by means of the eLORETA method. In particular, the subjects were classified as bad counters or good counters, according to the results of the task, and the brain activity of the two groups was compared. The results were statistically significant only in the beta band, revealing that the left limbic lobe was found to be more active in people showing better performance. The limbic lobe is involved in visuospatial processing, memory, arithmetic fact retrieval, and emotions. However, the role of the limbic lobe in mental arithmetic has been barely explored, so these interesting findings could represent a starting point for future in-depth analyses. Since there is evidence in the literature that the motor system is affected by the execution of arithmetic tasks, a more extensive knowledge of the brain activation associated with arithmetic tasks could be exploited not only for the assessment of mathematical skills but also in the evaluation of motor impairments and, consequently, in rehabilitation for motor disorders.

Relationship between Walking and Driving, and Cognitive Functioning Common to Both Modes of Mobility, in Healthy Older Adults

Introduction: Driving and walking, the two main modes of mobility, require numerous common skills in the motor, sensory, and cognitive domains that deteriorate with age. The objective of this study was to investigate the relationship between walking and driving in healthy older drivers and to determine whether certain cognitive processes are involved in both modes of mobility. Method: Seventy-six older drivers from the Safe Move cohort were assessed in the following three domains: (1) cognition, using parts A and B of the Trail Making Test (TMT), the digit symbol substitution test (DSST), the Stroop test, and the Digit span; (2) gait, using a dual-task (DT) paradigm with a counting task; and (3) driving, assessed via a 40–50 min on-road test. Analyses were also performed on 2 subgroups: young-old (70–74 years old; n = 43) and old-old (≥75 years; n = 33). Results: Four significant correlations were found across the whole sample between gait performance under DT conditions and driving scores. One correlation was also found in old-old adults. None were found in young-old adults. Furthermore, several cognitive measures were significantly correlated to both modes of mobility: TMT-A and B completion time in the whole sample, and DSST performance in the whole sample and old-old adults. Discussion/Conclusion: Walking in complex conditions and on-road driving performance are closely related in healthy older drivers. Visuospatial attention, processing speed, and executive function are crucial and common cognitive processes to both modes of mobility in this population. Impairment in these cognitive functions should thus alert health professionals as it can quickly lead to mobility disorders, loss of autonomy and social isolation. Developing specific preventive programs and mobility support systems for healthy older adults is also crucial.

A lateralized alpha-band marker of the interference of exogenous attention over endogenous attention.

Scientists differentiate top-down from bottom-up visuospatial attention processes. While bottom-up attention is rapidly engaged by emerging demands from the environment, top-down attention in contrast reflects slow voluntary shifts of spatial attention. Several lines of research substantiate the idea that top-down and bottom-up attentional processes involve distinct functional systems. An increasing number of studies, however, argue that both attention systems share brain processing resources. The current study examines how salient visual events that engage bottom-up processes interfere with top-down attentional processes. Using neurophysiological recordings and multivariate pattern classification techniques, the authors show that these patterns of interference occur within the alpha-band of neural activity (8-12Hz), which implies that bottom-up and top-down attention processes share this narrow-band frequency brain resource. The results further demonstrate that patterns of alpha-band activity explains, in part, the interference between top-down and bottom-up attention at the behavioral level.

Amyloid and Tau Predominance Subtyping Identifies CI Patients With Different Clinical Phenotypes

AbstractBackgroundThe ATN classification system assumes a sequential model of disease progression. However, there are groups of individuals in the same ATN category that exhibit a predominance of abnormality (higher burden) of one of the biomarkers, creating heterogeneous ATN groups regarding pathological predominance. Thus, we tested the hypothesis that individuals clustered by ATN biomarker abnormality predominance may offer an alternative to groups defined using biomarkers cut‐offs.MethodWe assessed 103 cognitively impaired individuals(CDR> = 0.5) from the TRIAD cohort with available measures of plasma phosphorylated tau‐181, brain MRI, amyloid PET, and tau PET. We used the K‐means algorithm to stratify participants into three clusters. We compared the clusters on composite measures of memory, executive functioning, language, and visuospatial processing. To examine the utility of the discovered clusters, we compared them to traditional ATN categories in the prediction of neuropsychological measures. We did so by creating three categories: patients positive on all three ATN biomarkers, patients positive on two of the three biomarkers, and patients positive on either one or none. Additionally, we created an inflammation, amyloid and tau deposition probabilistic map anchored on young controls(n = 51, mean age = 23.74).ResultsWe uncovered 3 clusters: an amyloid predominant (AP) cluster, a tau/phosphor‐tau predominant cluster (TP), and a cluster showing no predominance with low levels on all biomarkers (CN)(figure 1). Notably, levels of neurodegeneration and inflammation were similar between the AP and TP clusters. The AP cluster significantly differed from the CN cluster in memory only. Participants in the TP cluster had significantly lower scores in memory, executive functioning, language, and visuospatial processing than the other two clusters. In comparison, using threshold‐based ATN groups showed milder differences in memory and executive functioning, and no differences in language and visuospatial processing(figure 2). Furthermore, cluster membership moderated the relationship between various biomarkers, to the point of reversing the direction of correlation(figure 3).ConclusionOur results highlight the biological heterogeneity present within the Alzheimer’s disease continuum and that the pathological predominance of amyloid and tau is associated with different disease phenotypes. Approaching dementia patients with an eye on the predominance of pathology rather than cutoffs for abnormality may provide a better understanding of AD pathological subtypes.

Amyloid and Tau Predominance Subtyping Identifies CI Patients With Different Clinical Phenotypes

AbstractBackgroundThe ATN classification system assumes a sequential model of disease progression. However, there are groups of individuals in the same ATN category that exhibit a predominance of abnormality (higher burden) of one of the biomarkers, creating heterogeneous ATN groups regarding pathological predominance. Thus, we tested the hypothesis that individuals clustered by ATN biomarker abnormality predominance may offer an alternative to groups defined using biomarkers cut‐offs.MethodWe assessed 103 cognitively impaired individuals(CDR> = 0.5) from the TRIAD cohort with available measures of plasma phosphorylated tau‐181, brain MRI, amyloid PET, and tau PET. We used the K‐means algorithm to stratify participants into three clusters. We compared the clusters on composite measures of memory, executive functioning, language, and visuospatial processing. To examine the utility of the discovered clusters, we compared them to traditional ATN categories in the prediction of neuropsychological measures. We did so by creating three categories: patients positive on all three ATN biomarkers, patients positive on two of the three biomarkers, and patients positive on either one or none. Additionally, we created an inflammation, amyloid and tau deposition probabilistic map anchored on young controls(n = 51, mean age = 23.74).ResultWe uncovered 3 clusters: an amyloid predominant (AP) cluster, a tau/phosphor‐tau predominant cluster (TP), and a cluster showing no predominance with low levels on all biomarkers (CN)(figure 1). Notably, levels of neurodegeneration and inflammation were similar between the AP and TP clusters. The AP cluster significantly differed from the CN cluster in memory only. Participants in the TP cluster had significantly lower scores in memory, executive functioning, language, and visuospatial processing than the other two clusters. In comparison, using threshold‐based ATN groups showed milder differences in memory and executive functioning, and no differences in language and visuospatial processing(figure 2). Furthermore, cluster membership moderated the relationship between various biomarkers, to the point of reversing the direction of correlation(figure 3).ConclusionOur results highlight the biological heterogeneity present within the Alzheimer’s disease continuum and that the pathological predominance of amyloid and tau is associated with different disease phenotypes. Approaching dementia patients with an eye on the predominance of pathology rather than cutoffs for abnormality may provide a better understanding of AD pathological subtypes.

Tau epicenter identification and connectivity in clinically heterogeneous Alzheimer’s disease variants

AbstractBackgroundWhile the spread of tau throughout the brain is well‐characterized in amnestic Alzheimer’s disease (AD), tau staging remains less clear for those suffering from clinically heterogeneous variants including logopenic variant primary progressive aphasia (lvPPA) and posterior cortical atrophy (PCA). We created a method to identify local maxima of tau SUVR (“epicenters”) in participants with early‐stage clinically heterogeneous AD with the goal of classifying participant subtypes based on the functional connectivity of these epicenters.MethodWe obtained 18F‐MK‐6240 tau PET scans from 10 participants with diagnoses of early‐stage clinically heterogeneous AD (5 lvPPA, 5 PCA, Clinical Dementia Rating 0.5‐1.0). We identified three local maxima of tau SUVR with a minimum specified distance of 20mm between them for each participant (Fig. 1). We then derived each epicenter’s functional connectivity in 1000 healthy controls using Neurosynth and sorted participants into subtypes based on the overlap of these functional connectivity maps.ResultParticipants with lvPPA showed highest tau burden in the posterior temporoparietal and temporoocciptal regions, left side predominant, and participants with PCA displayed highest tau burden in the bilateral parietooccipital cortex, frontal eye fields, and fusiform gyrus. We identified nine distinct subtypes of functional connectivity and most participants’ epicenters participated in more than one subtype. All subtypes highlight functional connectivity networks that have been associated with language and, or visuospatial processing. The most common subtype (seen in 7 of the 10 participants and 11 of the 30 epicenters) features connectivity within the bilateral occipital lobule, fusiform gyrus, and superior parietal lobule (Fig. 2).ConclusionWe used a novel method to identify tau “epicenters” in the brains of participants with early‐stage clinically heterogeneous AD. Using these epicenters, we derived functional connectivity maps, which we then grouped into nine subtypes across participants. We will shortly begin collecting longitudinal tau PET in these clinically heterogeneous individuals with AD, allowing us to assess the extent to which tau spreads along the functional connectivity maps predicted by each participant’s epicenters and whether individually tailored epicenters outperform subtype classification. This work could serve as the basis for patient‐specific biomarkers of expected disease spread in clinically heterogeneous AD.

Similarities and differences in cognition as a function of sex: A longitudinal study of healthy control participants from the Parkinson Progression Markers Initiative

AbstractBackgroundAs the global population of older adults continues to rise, there is an urgent need to understand the expected cognitive changes in healthy aging. Despite sex‐based differences in life expectancy and age‐related diseases such as Alzheimer’s disease, limited research has explicitly examined sex differences in aging. The objective of the current study was to answer three primary questions using longitudinal data for sample of healthy adults: 1) How does cognition change over time? 2) What are the sex differences in cognition? and 3) What are the sex differences in rates of cognitive change over time?MethodLongitudinal data from the healthy control group of the Parkinson’s Progression Markers Initiative was used to examine cognitive changes in healthy adult males (n = 125, mean age = 61.61, SD = 10.97) and females (n = 68, mean age = 59.44, SD = 11.56). Participants underwent annual neuropsychological testing for up to five years. A series of 2‐level linear mixed models estimated within‐person change in cognition over time (i.e., level‐1) and between‐group differences in longitudinal change trajectories as predicted by sex (i.e., level 2). Each neuropsychological measure was modeled separately as a single outcome variable, for a total of seven models.ResultStability in neuropsychological scores was seen over five years. At baseline, males scored higher on the Benton Judgement of Line Orientation Test, while females scored higher on the Symbol Digit Modalities Test, the Semantic Fluency Test, and the Hopkins Verbal Learning Test‐Revised. Rates of cognitive change over time did not significantly differ by sex. Higher age and lower education at baseline predicted lower neuropsychological scores.ConclusionStability in cognition was found across five years in a sample healthy control participants from a large multi‐site longitudinal study. Sex differences in cognition were found in several domains, including visuospatial ability, processing speed, verbal fluency, and verbal memory. However, rates of cognitive change over time did not significantly differ by sex. Higher age and lower education were predictive of lower cognitive functioning. Great intraindividual variability in cognitive trajectories was observed. Future research should continue to examine factors that predict individual trajectories of aging in healthy individuals.

Abnormality of the pulvinar in posterior cortical atrophy: A multimodal MRI study

AbstractBackgroundAlthough the pulvinar is known for its extensive connections with both ventral and dorsal visual streams, details of pulvinar functional connectivity in the setting of posterior cortical atrophy (PCA) remain unclearTo study pulvinar functional connectivity and relevant associations with higher visual dysfunction in PCA.MethodA total of 29 patients with PCA and 30 normal controls were recruited. Each participant underwent comprehensive neuropsychological assessment and both structural and resting‐state functional MRI scanning. Voxel‐based morphometry (VBM) and seed‐based functional connectivity analyses were conducted to assess pulvinar gray matter volume as well as connectivity between the pulvinar and whole brain regions. A partial correlation analysis was performed to analyze neuropsychological test and pulvinar imaging data.ResultCognitive and visual functions including visuospatial processing, visual perception, episodic memory, and naming were impaired among PCA patients. Marked pulvinar atrophy was noted in PCA patients. Furthermore, functional connectivity between the pulvinar and precuneus was significantly decreased in PCA patients as compared to normal controls (FWE corrected; P<0.001). Left pulvinar gray matter volume was found to associate with object agnosia (r = 0.42, P<0.05) and right–left disorientation (r = 0.29, P<0.05) among PCA patients. The bilateral pulvinar region was found to associate with Boston Naming Test (left, r = 0.51, P = 0.015; right, r = 0.46, P = 0.03) and Activities of Daily Living (left, r = ‐0.46, P = 0.019; right, r = ‐0.53, P = 0.006) scores. Correlation analyses did not reveal significant findings concerning functional connectivity.ConclusionOur findings confirm pulvinar degeneration and its contributions in the setting of PCA.

Visual imagery deficits in posterior cortical atrophy

ABSTRACT Visual imagery has a close overlapping relationship with visual perception. Posterior cortical atrophy (PCA) is a neurodegenerative syndrome marked by early impairments in visuospatial processing and visual object recognition. We asked whether PCA would therefore also be marked by deficits in visual imagery, tested using objective forced-choice questionnaires, and whether imagery deficits would be selective for certain properties. We recruited four patients with PCA and a patient with integrative visual agnosia due to bilateral occipitotemporal strokes for comparison. We administered a test battery probing imagery for object shape, size, colour lightness, hue, upper-case letters, lower-case letters, word shape, letter construction, and faces. All subjects showed significant impairments in visual imagery, with imagery for lower-case letters most likely to be spared. We conclude that PCA subjects can show severe deficits in visual imagery. Further work is needed to establish how frequently this occurs and how early it can be found.

Enhancement and contextual modulation of visuospatial processing by thalamocollicular projections from ventral lateral geniculate nucleus

In the mammalian visual system, the ventral lateral geniculate nucleus (vLGN) of the thalamus receives salient visual input from the retina and sends prominent GABAergic axons to the superior colliculus (SC). However, whether and how vLGN contributes to fundamental visual information processing remains largely unclear. Here, we report in mice that vLGN facilitates visually-guided approaching behavior mediated by the lateral SC and enhances the sensitivity of visual object detection. This can be attributed to the extremely broad spatial integration of vLGN neurons, as reflected in their much lower preferred spatial frequencies and broader spatial receptive fields than SC neurons. Through GABAergic thalamocollicular projections, vLGN specifically exerts prominent surround suppression of visuospatial processing in SC, leading to a fine tuning of SC preferences to higher spatial frequencies and smaller objects in a context-dependent manner. Thus, as an essential component of the central visual processing pathway, vLGN serves to refine and contextually modulate visuospatial processing in SC-mediated visuomotor behaviors via visually-driven long-range feedforward inhibition.

26 To 'Proxy’ or Not to 'Proxy’: The Differential Effects of Cognitive Reserve on Late-Life Neuropsychological Functioning

Objective:As the population continues to age at a rapid pace, an important question that has been raised by clinicians and researchers alike, is “how can we preserve our cognitive abilities as older adults?” Cognitive reserve (CR) is thought to account for inter-individual differences in the cognitive trajectories of older people experiencing similar levels of brain pathology. Being a hypothetical construct, CR cannot be measured directly and therefore, must be operationalized through a combination of demographic and lifestyle variables. While there is sufficient empirical evidence supporting the relationship between individual CR proxies and cognitive functioning, few studies to date have explored which CR proxy is most important in predicting aspects of late-life cognitive functioning and whether composite measure of CR accurately predict cognitive functioning, above and beyond variables traditionally associated with late-life cognitive ability (e.g., age, gender, cardiovascular risk, depression). The present cross-sectional study sought to examine the relationship between three well-established CR proxies—educational attainment, mental workplace demands, crystallized intelligence—and baseline neuropsychological functioning in a clinical sample of older adults without dementia.Participants and Methods:Using archival data from 248 older adult patients seen at geriatric specialist hospital in Ontario, Canada, we examined the cumulative and independent effects of educational attainment (years of formal education), mental workplace demands (mean analyst rating for 10 O*NET variables measuring cognitively complex work activities), and crystallized intelligence (score on WASI-I Vocabulary subtest) on performance across several neuropsychological tests assessing i.) verbal memory, ii.) visual memory, iii.) attention, concentration, and working memory, iv.) executive functioning, v.) visuospatial processing, and vi.) language. Composite scores for all six cognitive domains were calculated by averaging converted z-scores on domain-specific tests of neuropsychological functioning. A series of regression models were then constructed to evaluate the relationship between CR and late-life cognitive functioning. To determine the relative importance of each CR proxy, a follow-up relative weight analysis (RWA) was performed for each regression model.Results:After controlling for age, gender, cardiovascular risk, and depression, our composite measure of CR (average z-score of educational attainment, mental workplace demands, crystallized intelligence) proved to be a significant predictor across all domains of cognitive functioning. Of the six cognitive domains assessed, CR was the most important in predicting higher-order cognitive functions, such as working memory and executive functioning. Out of the three CR proxies, crystallized intelligence was the only CR proxy that significantly predicted performance across all six cognitive domains. RWA revealed that crystallized intelligence was the most important in predicting neuropsychological functioning, followed by educational attainment, and mental workplace demands.Conclusions:Despite being closely related, all three CR proxies demonstrated differential effects on late-life cognitive functioning. Overall, our findings suggest that the effects of CR are not generalizable across all cognitive domains and appears to be somewhat dependent on the CR proxy used. This study supports the existing literature in demonstrating the robustness of crystallized intelligence as a CR proxy and provides preliminary evidence supporting the idea that tasks that require higher levels of cognitive processing are the most influenced by CR.