Amelia M. Carton

Prominent effects and neural correlates of visual crowding in a neurodegenerative disease population.

Visual crowding is a perceptual phenomenon whereby recognition of a stimulus is disrupted by the presence of flanker stimuli. Yong et al. observe excessive crowding in individuals with a neurodegenerative condition (posterior cortical atrophy) and identify associations between prominent crowding and lower grey matter volume in the right collateral sulcus.

ApoE influences regional white-matter axonal density loss in Alzheimer's disease

Mechanisms underlying phenotypic heterogeneity in young onset Alzheimer disease (YOAD) are poorly understood. We used diffusion tensor imaging and neurite orientation dispersion and density imaging (NODDI) with tract-based spatial statistics to investigate apolipoprotein (APOE) ε4 modulation of white-matter damage in 37 patients with YOAD (22, 59% APOE ε4 positive) and 23 age-matched controls. Correlation between neurite density index (NDI) and neuropsychological performance was assessed in 4 white-matter regions of interest. White-matter disruption was more widespread in ε4+ individuals but more focal (posterior predominant) in the absence of an ε4 allele. NODDI metrics indicate fractional anisotropy changes are underpinned by combinations of axonal loss and morphological change. Regional NDI in parieto-occipital white matter correlated with visual object and spatial perception battery performance (right and left, both p = 0.02), and performance (nonverbal) intelligence (WASI matrices, right, p = 0.04). NODDI provides tissue-specific microstructural metrics of white-matter tract damage in YOAD, including NDI which correlates with focal cognitive deficits, and APOEε4 status is associated with different patterns of white-matter neurodegeneration.

Eyetracking Metrics in Young Onset Alzheimer’s Disease: A Window into Cognitive Visual Functions

Young onset Alzheimer’s disease (YOAD) is defined as symptom onset before the age of 65 years and is particularly associated with phenotypic heterogeneity. Atypical presentations, such as the clinic-radiological visual syndrome posterior cortical atrophy (PCA), often lead to delays in accurate diagnosis. Eyetracking has been used to demonstrate basic oculomotor impairments in individuals with dementia. In the present study, we aim to explore the relationship between eyetracking metrics and standard tests of visual cognition in individuals with YOAD. Fifty-seven participants were included: 36 individuals with YOAD (n = 26 typical AD; n = 10 PCA) and 21 age-matched healthy controls. Participants completed three eyetracking experiments: fixation, pro-saccade, and smooth pursuit tasks. Summary metrics were used as outcome measures and their predictive value explored looking at correlations with visuoperceptual and visuospatial metrics. Significant correlations between eyetracking metrics and standard visual cognitive estimates are reported. A machine-learning approach using a classification method based on the smooth pursuit raw eyetracking data discriminates with approximately 95% accuracy patients and controls in cross-validation tests. Results suggest that the eyetracking paradigms of a relatively simple and specific nature provide measures not only reflecting basic oculomotor characteristics but also predicting higher order visuospatial and visuoperceptual impairments. Eyetracking measures can represent extremely useful markers during the diagnostic phase and may be exploited as potential outcome measures for clinical trials.

Profiles in paint: contrasting responses to a common artistic exercise by people with different dementias

Abstract Paintings could offer insight into the varied experiences of people with different dementias. In this project, a single exercise – the painting of a group of objects in still-life – was used to capture artistic production in four artists with different diagnoses of dementia and four healthy artists. Whilst quantitative studies provide important insights into the neuroanatomical supports for artistic actions, autonomous art exercises may yield deeper understanding of the individual creative experience in the context of neurodegenerative disease.

Navigational cue effects in Alzheimer's disease and posterior cortical atrophy

Deficits in spatial navigation are characteristic and disabling features of typical Alzheimers disease (tAD) and posterior cortical atrophy (PCA). Visual cues have been proposed to mitigate such deficits; however, there is currently little empirical evidence for their use.

CAN EYETRACKING METRICS RELATE TO PERFORMANCE ON VISUAL COGNITIVE TESTS OF INDIVIDUALS WITH YOUNG-ONSET ALZHEIMER’S DISEASE?

compare AD patients with and without confabulations. Methods: 37 healthy control (HC) and 35 individuals with mild to moderate AD were recruited at the Piti e-Salpêtri ere University Hospital. All participants were evaluated on Dalla Barba’s Confabulation Battery to determine their tendency to produce provoked confabulations. Thus, among AD patients, we distinguish between those who produced episodic confabulations, and those who didn’t. Accordingly 27 AD patients were considered free of confabulations (ADC-), and 8 as confabulators (ADC+) (none HC met the criteria). Then, all participants were assessed on a comprehensive neuropsychological battery which evaluate notably episodic memory, language, executive functioning and working memory. Participants also went through a structural MRI to determine whether ADCand ADC+ are similar. Results:Statistical analyses showed a significant difference between HC participants and the two groups of AD patients, in almost all cognitive domains assessed in our battery. However when comparing the two AD groups, they didn’t demonstrate distinct profiles. Regarding the neuroimaging data, and particularly hippocampal subfields volumes, the results showed the same pattern. Conclusions: In demonstrating that there is no cognitive differences between patients with and without confabulations, our results put in doubt some confabulation models supposing a unique and sufficient cognitive (e.g. executive) process underlying the onset of confabulations.

MODELLING EYE-TRACKING DATA TO DISCRIMINATE BETWEEN ALZHEIMER'S PATIENTS AND HEALTHY CONTROLS

DET in-clinic 41 2.62 0.14 48 2.63 0.13 0.76 -0.06 unsupervised 33 2.62 0.11 36 2.65 0.13 0.45 -0.18 IDN in-clinic 41 2.78 0.10 48 2.79 0.10 0.64 -0.1 unsupervised 33 2.75 0.07 35 2.79 0.07 0.033 -0.12 OCL in-clinic 41 0.96 0.12 46 0.89 0.10 0.005 0.62 unsupervised 33 0.96 0.11 36 0.91 0.10 0.063 0.45 ONB in-clinic 41 2.96 0.10 47 3.01 0.11 0.052 -0.42 unsupervised 33 2.95 0.09 35 2.99 0.08 0.037 -0.51 Podium Presentations: Monday, July 17, 2017 P597

LONGITUDINAL EVALUATION OF NEUROPSYCHOLOGICAL AND NEUROIMAGING PROGRESSION IN POSTERIOR CORTICAL ATROPHY

Background: fNIRS is expected as a non-invasive and unconstrained neuroimaging modality used to measure activationinduced changes in cerebral hemoglobin concentration. By this technique, changes in the optical absorption of light over the region of interest on the brain during the task are measured to estimate the local cerebral vascular and oxygen metabolic effects so that the task design is most important factor for successful evaluation of brain functions. The objective of this study is to establish the most suitable fNIRS task which is easily to be executed in elderly subjects and indicates significant oxygenated Hb (Oxy-Hb) changes in Alzheimer’s disease (AD) patients with less cognitive ability. Methods:We designed eight kinds of tasks for fNIRS measurement for the elderly. The task is related to detect memory and sensate function, such as touching, hearing, and smelling. We investigated the adaptable task for AD subject that is easily to execute, to understand, and to obtain enough Oxy-Hb changes during task duration. fNIRS measurement was performed employing 54 channels that covered bilaterally over the frontal and parietal area from 22 healthy control subjects (between ages of 60 to 82) and 17 AD subjects (between ages of 60 to 78). A five trials of block design was applied for data acquisition. Results: Among eight tasks, cold stimulation and calculation tasks were simple and understandable tasks and most suitable for fNIRS measurement in AD. From the fNIRS recording data, while, in healthy elder subjects, the typical oxy-Hb concentration change patterns showing significant increase in the local area of the left prefrontal cortex during cold stimulation task in the right hand, AD patients showed significant decrease compared to the healthy control. Conclusions: We have investigated most suitable fNIRS tasks which is easily to be executed for eldered AD subjects, and differences in OxyHb changes by task activation between normal control and AD. fNIRS might have the potential to become either a disease or syndrome-specific diagnostic tool in the future.

Locomotion and eye behaviour under controlled environment in individuals with Alzheimer's disease

This study aimed to examine simple locomotion and eye behaviour of individuals with Posterior Cortical Atrophy (PCA) and typical Alzheimers disease (tAD) within a simulated real-world environment. Posterior cortical atrophy (PCA) is a neurodegenerative condition characterised by parietal, occipital and occipito-temporal tissue loss and progressive impairment of higher-order visual function in contrast to relatively spared memory and language. Targeted types of locomotion were walking in a series of corridors, up or down stairs, and across an open room with or without the presence of an obstacle. Eye tracking measures and inertial moment units (IMU) were used in this experiment, and resultant acceleration of left foot and fixation duration were extracted. Findings from three participants are presented as a case series: one control, one PCA and one tAD patient. The averaged resultant acceleration of PCA patient was the slowest in all types of locomotion, especially in stairs. The averaged resultant accelerations of PCA and tAD participants were slower than the control participant. The PCA participant had longer mean fixation durations than the tAD and control participants, however, mean fixation duration was similar between tAD and control participants. Results may help characterise locomotion and eye behaviour in PCA and tAD and may suggest ways to support effective diagnosis and assessment of disease progression.