The neuropathology of the occipital cortex and its significance in the visual problems of patients with variant Creutzfeldt-Jakob Disease (vCJD)

The occipital lobe is one of the cortical areas most affected by the pathology of variant Creutzfeldt-Jakob disease (vCJD). To understand the visual problems of vCJD patients, neuropathological changes were studied in striate (B17, V1) and extrastriate (B18, V2) regions of the occipital cortex in eleven cases of vCJD. No differences in the density of vacuoles or surviving neurons were observed in B17 and B18 but densities of glial cell nuclei and deposits of the protease resistant form of prion protein (PrPsc) were greater in B18. The density of PrPsc deposits in B17 was positively correlated with their density in B18. The density of the diffuse PrPsc deposits in B17 was negatively correlated with the density of the surviving neurons in B18. In B17 and B18, the vacuoles either exhibited density peaks in laminae II/III and V/VI or were more uniformly distributed across the laminae. Diffuse PrPsc deposits were most frequent in laminae II/III and florid PrPsc deposits more generally distributed. In B18, the surviving neurons were more consistently bimodally distributed and the glial cell nuclei most abundant in laminae V/VI compared with B17. Hence, both striate and extrastriate areas of the occipital cortex are affected by the pathology of vCJD, the pathological changes being most severe in B18. Neuronal degeneration in B18 may be associated with the development of diffuse PrPsc deposits in B17. These data suggest that the short cortico-cortical connections between B17 and B18 and the pathways to subcortical visual areas are compromised in vCJD. Pathological changes in striate and extrastriate regions of the occipital cortex may contribute to several of the visual problems identified in patients with vCJD including oculomotor and visuo-spatial function. © 2012 Nova Science Publishers, Inc. All rights reserved.

Oculo-visual dysfunction in Parkinson's disease

This review describes the oculo-visual problems likely to be encountered in Parkinson's disease (PD) with special reference to three questions: (1) are there visual symptoms characteristic of the prodromal phase of PD, (2) is PD dementia associated with specific visual changes, and (3) can visual symptoms help in the differential diagnosis of the parkinsonian syndromes, viz. PD, progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and corticobasal degeneration (CBD)? Oculo-visual dysfunction in PD can involve visual acuity, dynamic contrast sensitivity, colour discrimination, pupil reactivity, eye movement, motion perception, and visual processing speeds. In addition, disturbance of visuo-spatial orientation, facial recognition problems, and chronic visual hallucinations may be present. Prodromal features of PD may include autonomic system dysfunction potentially affecting pupil reactivity, abnormal colour vision, abnormal stereopsis associated with postural instability, defects in smooth pursuit eye movements, and deficits in visuo-motor adaptation, especially when accompanied by idiopathic rapid eye movement (REM) sleep behaviour disorder. PD dementia is associated with the exacerbation of many oculo-visual problems but those involving eye movements, visuo-spatial function, and visual hallucinations are most characteristic. Useful diagnostic features in differentiating the parkinsonian symptoms are the presence of visual hallucinations, visuo-spatial problems, and variation in saccadic eye movement dysfunction.

Spatial perspective taking is an embodied process, but not for everyone in the same way:differences predicted by sex and social skills score

We re-analysed visuo-spatial perspective taking data from Kessler and Thomson (2010) plus a previously unpublished pilot with respect to individual- and sex differences in embodied processing (defined as body-posture congruence effects). We found that so-called 'systemisers' (males/low-social-skills) showed weaker embodiment than so-called 'embodiers' (females/high-social-skills). We conclude that 'systemisers' either have difficulties with embodied processing or, alternatively, they have a strategic advantage in selecting different mechanisms or the appropriate level of embodiment. In contrast, 'embodiers' have an advantageous strategy of "deep" embodied processing reflecting their urge to empathise or, alternatively, less flexibility in fine-tuning the involvement of bodily representations. © 2012 Copyright Taylor and Francis Group, LLC.

A cross-culture, cross-gender comparison of perspective taking mechanisms

Being able to judge another person's visuo-spatial perspective is an essential social skill, hence we investigated the generalizability of the involved mechanisms across cultures and genders. Developmental, cross-species, and our own previous research suggest that two different forms of perspective taking can be distinguished, which are subserved by two distinct mechanisms. The simpler form relies on inferring another's line-of-sight, whereas the more complex form depends on embodied transformation into the other's orientation in form of a simulated body rotation. Our current results suggest that, in principle, the same basic mechanisms are employed by males and females in both, East-Asian (EA; Chinese) and Western culture. However, we also confirmed the hypothesis that Westerners show an egocentric bias, whereas EAs reveal an other-oriented bias. Furthermore, Westerners were slower overall than EAs and showed stronger gender differences in speed and depth of embodied processing. Our findings substantiate differences and communalities in social cognition mechanisms across genders and two cultures and suggest that cultural evolution or transmission should take gender as a modulating variable into account.

Weight loss strategies, stress, and cognitive function:supervised versus unsupervised dieting

The early stages of dieting to lose weight have been associated with neuro-psychological impairments. Previous work has not elucidated whether these impairments are a function solely of unsupported or supported dieting. Raised cortico-steroid levels have been implicated as a possible causal mechanism. Healthy, overweight, pre-menopausal women were randomised to one of three conditions in which they dieted either as part of a commercially available weight loss group, dieted without any group support or acted as non-dieting controls for 8 weeks. Testing occurred at baseline and at 1, 4 and 8 weeks post baseline. During each session, participants completed measures of simple reaction time, motor speed, vigilance, immediate verbal recall, visuo-spatial processing and (at Week 1 only) executive function. Cortisol levels were gathered at the beginning and 30 min into each test session, via saliva samples. Also, food intake was self-recorded prior to each session and fasting body weight and percentage body fat were measured at each session. Participants in the unsupported diet condition displayed poorer vigilance performance (p=0.001) and impaired executive planning function (p=0.013) (along with a marginally significant trend for poorer visual recall (p=0.089)) after 1 week of dieting. No such impairments were observed in the other two groups. In addition, the unsupported dieters experienced a significant rise in salivary cortisol levels after 1 week of dieting (p<0.001). Both dieting groups lost roughly the same amount of body mass (p=0.011) over the course of the 8 weeks of dieting, although only the unsupported dieters experienced a significant drop in percentage body fat over the course of dieting (p=0.016). The precise causal nature of the relationship between stress, cortisol, unsupported dieting and cognitive function is, however, uncertain and should be the focus of further research. © 2005 Elsevier Ltd. All rights reserved.

Where do bright ideas occur in our brain? Meta-analytic evidence from neuroimaging studies of domain-specific creativity

Many studies have assessed the neural underpinnings of creativity, failing to find a clear anatomical localization. We aimed to provide evidence for a multi-componential neural system for creativity. We applied a general activation likelihood estimation (ALE) meta-analysis to 45 fMRI studies. Three individual ALE analyses were performed to assess creativity in different cognitive domains (Musical, Verbal, and Visuo-spatial). The general ALE revealed that creativity relies on clusters of activations in the bilateral occipital, parietal, frontal, and temporal lobes. The individual ALE revealed different maximal activation in different domains. Musical creativity yields activations in the bilateral medial frontal gyrus, in the left cingulate gyrus, middle frontal gyrus, and inferior parietal lobule and in the right postcentral and fusiform gyri. Verbal creativity yields activations mainly located in the left hemisphere, in the prefrontal cortex, middle and superior temporal gyri, inferior parietal lobule, postcentral and supramarginal gyri, middle occipital gyrus, and insula. The right inferior frontal gyrus and the lingual gyrus were also activated. Visuo-spatial creativity activates the right middle and inferior frontal gyri, the bilateral thalamus and the left precentral gyrus. This evidence suggests that creativity relies on multi-componential neural networks and that different creativity domains depend on different brain regions.

Body representation alterations in personal but not in extrapersonal neglect patients

There is still a matter of debate around the nature of personal neglect. Is it an attention disorder or a body representation disorder? Here we investigate the presence of body representation deficits (i.e., the visuo-spatial body map) in right and left brain-damaged patients and in particular in those affected by personal neglect. 23 unilateral brain-damaged patients (5 left-brain-damaged and 18 right-brain-damaged patients) and 15 healthy controls took part in the study. The visuo-spatial body map was assessed by means of the “Frontal body-evocation subtest (FBE),” in which participants have to put tiles representing body parts on a small wooden board where only the head is depicted as a reference point. In order to compare performance on the FBE with performance on an inanimate object that had well-defined right and left sides, participants also performed the “Car test.” Group statistical analysis shows that the performance of patients with personal neglect is significantly worse than that of the controls and patients without personal neglect in the FBE but not in the Car test. Single case analyses of the five patients with pure personal neglect confirm the results of group analysis. Our data supports the hypothesis that personal neglect is a pervasive body representation disorder.

Cognitive-behavioural phenotype in a group of girls from 1.2 to 12 years old with the Incontinentia Pigmenti syndrome:recommendations for clinical management

Incontinentia Pigmenti (IP, OMIM#308300) is a rare X-linked genomic disorder (about 1,400 cases) that affects the neuroectodermal tissue and Central Nervous System (CNS). The objective of this study was to describe the cognitive-behavioural profile in children in order to plan a clinical intervention to improve their quality of life. A total of 14 girls (age range: from 1 year and 2 months to 12 years and 10 months) with IP and the IKBKG/NEMO gene deletion were submitted to a cognitive assessment including intelligence scales, language and visuo-spatial competence tests, learning ability tests, and a behavioural assessment. Five girls had severe to mild intellectual deficiencies and the remaining nine had a normal neurodevelopment. Four girls were of school age and two of these showed no intellectual disability, but had specific disabilities in calculation and arithmetic reasoning. This is the first description of the cognitive-behavioural profile in relation to developmental age. We stress the importance of an early assessment of learning abilities in individuals with IP without intellectual deficiencies to prevent the onset of any such deficit.

Le profil alimentaire des enfants présentant un trouble envahissant du développement : un lien avec l'âge et le diagnostic

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Les relations entre les facteurs mentaux en entraînement, l'expérimentation du "flow" en compétition et la performance sportive lors d'une phase préparatoire et compétitive d'un même cycle annuel

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Mécanismes de contrôle du mouvement humain lors du port de verres à foyer progressif

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Deliberate and spontaneous sensations of disembodiment:capacity or flaw?

Introduction: Hallucinations that involve shifts in the subjectively experienced location of the self, have been termed “out-of-body experiences” (OBEs). Early psychiatric accounts cast OBEs as a specific instance of depersonalisation and derealisation disorder (DPD-DR). However, during feelings of alienation and lack of body realism in DPD-DR the self is experienced within the physical body. Deliberate forms of “disembodiment” enable humans to imagine another’s visuo-spatial perspective taking (VPT), thus, if a strong relationship between deliberate and spontaneous forms of disembodiment could be revealed, then uncontrolled OBEs could be “the other side of the coin” of a uniquely human capacity. Methods: We present a narrative review of behavioural and neuroimaging work emphasising methodological and theoretical aspects of OBE and VPT research and a potential relationship. Results: Results regarding a direct behavioural relationship between VPT and OBE are mixed and we discuss reasons by pointing out the importance of using realistic tasks and recruiting genuine OBEers instead of general DPD-DR patients. Furthermore, we review neuroimaging evidence showing overlapping neural substrates between VPT and OBE, providing a strong argument for a relationship between the two processes. Conclusions: We conclude that OBE should be regarded as a necessary implication of VPT ability in humans, or even as a necessary and potentially sufficient condition for the evolution of VPT.

Visual signs and symptoms of corticobasal degeneration

Corticobasal degeneration is a rare, progressive neurodegenerative disease and a member of the 'parkinsonian' group of disorders, which also includes Parkinson's disease, progressive supranuclear palsy, dementia with Lewy bodies and multiple system atrophy. The most common initial symptom is limb clumsiness, usually affecting one side of the body, with or without accompanying rigidity or tremor. Subsequently, the disease affects gait and there is a slow progression to influence ipsilateral arms and legs. Apraxia and dementia are the most common cortical signs. Corticobasal degeneration can be difficult to distinguish from other parkinsonian syndromes but if ocular signs and symptoms are present, they may aid clinical diagnosis. Typical ocular features include increased latency of saccadic eye movements ipsilateral to the side exhibiting apraxia, impaired smooth pursuit movements and visuo-spatial dysfunction, especially involving spatial rather than object-based tasks. Less typical features include reduction in saccadic velocity, vertical gaze palsy, visual hallucinations, sleep disturbance and an impaired electroretinogram. Aspects of primary vision such as visual acuity and colour vision are usually unaffected. Management of the condition to deal with problems of walking, movement, daily tasks and speech problems is an important aspect of the disease.

Exploitation du potentiel sismique des étoiles naines blanches

Le but de cette thèse est d’explorer le potentiel sismique des étoiles naines blanches pulsantes, et en particulier celles à atmosphères riches en hydrogène, les étoiles ZZ Ceti. La technique d’astérosismologie exploite l’information contenue dans les modes normaux de vibration qui peuvent être excités lors de phases particulières de l’évolution d’une étoile. Ces modes modulent le flux émergent de l’étoile pulsante et se manifestent principalement en termes de variations lumineuses multi-périodiques. L’astérosismologie consiste donc à examiner la luminosité d’étoiles pulsantes en fonction du temps, afin d’en extraire les périodes, les amplitudes apparentes, ainsi que les phases relatives des modes de pulsation détectés, en utilisant des méthodes standards de traitement de signal, telles que des techniques de Fourier. L’étape suivante consiste à comparer les périodes de pulsation observées avec des périodes générées par un modèle stellaire en cherchant l’accord optimal avec un modèle physique reconstituant le plus fidèlement possible l’étoile pulsante. Afin d’assurer une recherche optimale dans l’espace des paramètres, il est nécessaire d’avoir de bons modèles physiques, un algorithme d’optimisation de comparaison de périodes efficace, et une puissance de calcul considérable. Les périodes des modes de pulsation de modèles stellaires de naines blanches peuvent être généralement calculées de manière précise et fiable sur la base de la théorie linéaire des pulsations stellaires dans sa version adiabatique. Afin de définir dans son ensemble un modèle statique de naine blanche propre à l’analyse astérosismologique, il est nécessaire de spécifier la gravité de surface, la température effective, ainsi que différents paramètres décrivant la disposition en couche de l’enveloppe. En utilisant parallèlement les informations obtenues de manière indépendante (température effective et gravité de surface) par la méthode spectroscopique, il devient possible de vérifier la validité de la solution obtenue et de restreindre de manière remarquable l’espace des paramètres. L’exercice astérosismologique, s’il est réussi, mène donc à la détermination précise des paramètres de la structure globale de l’étoile pulsante et fournit de l’information unique sur sa structure interne et l’état de sa phase évolutive. On présente dans cette thèse l’analyse complète réussie, de l’extraction des fréquences à la solution sismique, de quatre étoiles naines blanches pulsantes. Il a été possible de déterminer les paramètres structuraux de ces étoiles et de les comparer remarquablement à toutes les contraintes indépendantes disponibles dans la littérature, mais aussi d’inférer sur la dynamique interne et de reconstruire le profil de rotation interne. Dans un premier temps, on analyse le duo d’étoiles ZZ Ceti, GD 165 et Ross 548, afin de comprendre les différences entre leurs propriétés de pulsation, malgré le fait qu’elles soient des étoiles similaires en tout point, spectroscopiquement parlant. L’analyse sismique révèle des structures internes différentes, et dévoile la sensibilité de certains modes de pulsation à la composition interne du noyau de l’étoile. Afin de palier à cette sensibilité, nouvellement découverte, et de rivaliser avec les données de qualité exceptionnelle que nous fournissent les missions spatiales Kepler et Kepler2, on développe une nouvelle paramétrisation des profils chimiques dans le coeur, et on valide la robustesse de notre technique et de nos modèles par de nombreux tests. Avec en main la nouvelle paramétrisation du noyau, on décroche enfin le ”Saint Graal” de l’astérosismologie, en étant capable de reproduire pour la première fois les périodes observées à la précision des observations, dans le cas de l’étude sismique des étoiles KIC 08626021 et de GD 1212.

Le profil alimentaire des enfants présentant un trouble envahissant du développement : un lien avec l'âge et le diagnostic

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.