Research suggests that the cerebellum is involved in cognition, but its exact role is unclear. The efficiency theory posits that the cerebellum supports processing speed. Other researchers argue that the cerebellum is functionally heterogeneous, and damage to lobes of the cerebellum causes selective loss of cognitive functions. This study sought to determine whether selective impairment in motor, verbal fluency, or processing speed occurred depending on the lobe of the cerebellum that was lesioned. Lesion mapping was used to measure lesion size and volumetric methods were used to measure atrophy in 25 adult survivors of cerebellar tumors. Participants had too a high degree of heterogeneous cerebellar lesions and accompanying atrophy to explore specialization. However, total cerebellar atrophy negatively impacted written and oral processing speed to a greater degree than total cerebellar lesion size. Younger ages at diagnosis and radiation therapy were associated with greater cerebellar atrophy.

The Finite Element Method of stress analysis is employed in axisymmetric, two and three-dimensional forms, to investigate the mechanical behaviour of dental structures under simulated oral loading conditions. Stress distributions which are examined, include those occuring in the crowns of normal teeth due to masticatory loading and in restored teeth as a consequence of the restoration's setting and thermal expansions. The force distributions occuring on roots of individual teeth and on teeth used as abutments for various bridge constructions are also investigated for both axial and non-axial loading and various alveolar bone support conditions. The instantaneous centres of rotation of teeth when subjected to orthodontic loading are also determined. The Finite Element Method is employed to examine various published hypotheses which attempt to correlate the mechanical behaviour of bone structures with that tissue's biological response characteristics. The cases examined include the remodelling of the alveolar process subsequent to orthodontic treatment and the remodelling or so-called straightening of the malaligned long bone. Utilising published experimental data, the Finite Element Method is also employed in a reverse mode to enable some hitherto unknown mechanical properties of the periodontal membrane and cortical bone tissues to be determined. Indeed, due to the flexibility of the method, it was possible to represent these tissues as orthotropic materials. The work is presented in two volumes. While the first volume contains all the results of the analyses, the second contains an outline of the relevant finite element theory. Nevertheless, where the theory has been extended, in particular in the area of non-isotropic material analysis, it is developed in greater depth. The second volume also contains both a thorough description and a listing of all the computer programs developed.

Hip fracture has been identified as one of the main health problems in the elderly. To improve the accuracy in assessing subject-specific hip fracture risk, this study proposed normalized cortical bone thickness (NCBT) estimated from patient’s hip DXA as an alternative predictor of hip fracture risk. Hip fracture risk index (HFRI) derived from DXA-based finite element model was utilized as a baseline for evaluating the effectiveness of NCBT in predicting hip fracture risk. It was found that NCBT at the lateral side of the narrowest femoral neck had the strongest correlation with femoral neck HFRI among the six locations of the proximal femur. This study suggests that it is possible to use NCBT as a surrogate for a quick evaluation of hip fracture risk. Yet its clinical performances such as sensitivity to therapy effectiveness and the ability to discriminate clinical fracture cases will be investigated in a future study.

Depuis les années 50 sont apparues, comme domaine d'étude, ce que l'on appelle les sciences cognitives, qui ont fédéré des disciplines telles que, entre autres, la neurobiologie, la psychologie, la philosophie, la linguistique... et bien entendu l'informatique. Sans revenir sur l'historique de la constitution des sciences cognitives, nous en retiendrons qu'elles sont apparues à partir du moment o'u les sciences sont devenues capables d'aborder la question de la conscience, en décortiquant et objectivant les phénomènes de mémoire, de perception, de langage et d'émotions. Objectiver le sujet, qui est au cœur des sciences cognitives, est l'expression d'un paradoxe dont nous parlerons dans ce chapitre, et la science informatique y a pris toute sa part. L'Intelligence Artificielle (IA) a été le versant en informatique des sciences cognitives. Parler d'intelligence artificielle fait d'ailleurs toujours l'objet de polémiques, la question de savoir jusqu'où l'on peut dire qu'une machine est capable d'intelligence n'étant pas tranchée aujourd'hui. Face à cette indétermination, nous soutiendrons l'hypothèse dite de l'IA forte, qui propose de considérer que l'ensemble de ce que l'on peut observer chez l'homme en termes de langage, pensée, conscience, est strictement le fruit de son métabolisme, neuronal en particulier. Nous ne demanderons pas au lecteur d'adhérer à cette hypothèse, mais soulignons ici qu'elle motive les travaux et les orientations de recherches que nous présentons dans ce mémoire. L'hypothèse d'IA forte trouve un écho particulier en informatique pour les raisons suivantes. L'informatique est une discipline qui dès l'origine [Turing, 1936; Church, 1936] a su abstraire la mécanique du traitement de l'information de son support. En effet, les machines de Turing ont existé bien avant d'être instanciées sur support physique. Selon cette perspective, qu'un traitement soit effectué sur silicium, au sein d'une clepsydre améliorée, ou sur un support neuronal ne change rien à l'affaire. La métaphore de la chambre chinoise de John Searle [Searle, 1980] illustre cette indépendance au support. Elle compare l'ordinateur à une personne enfermée dans une salle qui manipule des symboles chinois auxquels elle ne comprend rien, suivant pour ce faire un système de règles. Si l'on adhère à l'hypothèse d'IA forte, ce que ne fait pas Searle, le système de règles pourrait décrire une intelligence, équivalente à celle de l'Homme, dont l'opérateur est le moteur. Ce qui motive notre recherche informatique est l'hypothèse de l'existence de ces règles, autrement dit, d'un programme qui conduise 'a ce qu'une intelligence de même nature que celle de l'Homme puisse être instanciée par une machine de Turing. Faire cette hypothèse, toutefois, ne permet pas de guider la conception du programme, ou plutôt d'un programme, qui puisse doter une machine d'intelligence. Il est alors nécessaire de trouver ailleurs les arguments permettant de concevoir ces programmes. Là encore, l'hypothèse d'IA forte joue un rôle central. Si on admet que l'intelligence dont l'Homme fait preuve n'est que le résultat de la mécanique de ses neurones, il devient pertinent de s'inspirer des neurones 1Chapitre 1. Préambule pour concevoir un programme intelligent. L'argument ici n'est pas de dire que la voie neuromimétique est la seule qui puisse permettre de concevoir des machines intelligentes, mais plutôt de souligner que, sous l'hypothèse d'IA forte, cette voie permettra d'aboutir. En plus de cette garantie de succès, toute théorique car rien ne dit que la technologie permettra d'instancier ces machines, l'inspiration des neurones a un autre avantage pour l'informatique, qui se défend sans recourir à l'hypothèse d'IA forte. En effet, qu'ils suffisent ou non à rendre compte de l'intelligence, les mécanismes neuronaux qui s'expriment au sein du système nerveux sont un exemple de traitement de l'information de nature foncièrement différente de ceux conçus par les approches classiques de génie logiciel. L'étude de ces systèmes est alors susceptible d'apporter à l'informatique des paradigmes nouveaux, et c'est ce que nous défendons le plus ardemment dans nos travaux de recherche. L'ensemble de ce chapitre consiste 'a préciser ces quelques lignes d'introduction, en abordant le talon d'Achille des sciences cognitives, 'a savoir la question de la définition de l'intelligence. Nous abordons ensuite la question de la pluridisciplinarité, saisie du point de vue de l'informatique, pour défendre l'apport des sciences dites " molles " à notre discipline. Nous nous trouvons en effet dans la situation où un recours aux sciences humaines et sociales peut être défendu comme une aide pour débloquer les difficultés que rencontrent des sciences pourtant " dures " lorsqu'elles abordent la question de l'intelligence.

Neuro-engineering is an emerging multi-disciplinary domain which investigates the electrophysiological activities of the nervous system. It provides procedures and techniques to explore, analyze and characterize the functions of the different components comprising the nervous system. Neuro-engineering is not limited to research applications; it is employed in developing unconventional therapeutic techniques for treating different neurological disorders and restoring lost sensory or motor functions. Microelectrodes are principal elements in functional electric stimulation (FES) systems used in electrophysiological procedures. They are used in establishing an interface with the individual neurons or in clusters to record activities and communications, as well as modulate neuron behaviour through stimulation. Microelectrode technologies progressed through several modifications and innovations to improve their functionality and usability. However, conventional electrode technologies are open to further development, and advancement in microelectrodes technology will progressively meliorate the neuro-interfacing and electrotherapeutic techniques. This research introduced design methodology and fabrication processes for intra-cortical microelectrodes capable of befitting a wide range of design requirements and applications. The design process was employed in developing and implementing an ensemble of intra-cortical microelectrodes customized for different neuro-interfacing applications. The proposed designs presented several innovations and novelties. The research addressed practical considerations including assembly and interconnection to external circuitry. The research was concluded by exhibiting the Waterloo Array which is a high channel count flexible 3-D neuro-interfacing array. Finally, the dissertation was concluded by demonstrating the characterization, in vitro and acute in vivo testing results of the Waterloo Array. The implemented electrodes were tested and benchmarked against commercial equivalents and the results manifested improvement in the electrode performance compared to conventional electrodes. Electrode testing and evaluation were conducted in the Krembil Neuroscience Centre Research Lab (Toronto Western Hospital), and the Neurosciences & Mental Health Research Institute (the Sick Kids hospital). The research results and outcomes are currently being employed in developing chronic intra-cortical and electrocorticography (ECoG) electrode arrays for the epilepsy research and rodents nervous system investigations. The introduced electrode technologies will be used to develop customized designs for the clinical research labs collaborating with CIRFE Lab.

Traumatic brain injury (TBI) is an injury of the brain most often caused by blunt force trauma to the head and typically characterized by an increase in reactive oxygen species (ROS), inflammation, and hemorrhaging. Heme oxygenase (HO) catalyzes the breakdown of heme into carbon monoxide (CO), biliverdin which is further reduced to bilirubin, and ferrous iron. There are two active isoforms: HO-1 which is inducible and found predominantly in liver and spleen tissue; and HO-2 which is constitutive and found predominantly in the brain and testis. The metabolites of heme possess cytoprotective properties that can limit damage resulting from TBI. Our laboratory has found a selective HO-2 activator known as menadione (MD) that has been found to increase HO-2 activity by 4-fold while not affecting HO-1 in vitro. Given the higher amounts of HO-2 found in the brain and the cytoprotective properties of heme metabolites, we postulate that activation of HO-2 using menadione would mitigate further damage after TBI. The rat controlled cortical impact (CCI) model was used to simulate TBI with spontaneous locomotor activity (SLA), spontaneous alternation behaviour (SAB), and beam balance (BB) as the behavioural tasks to assess cognitive and motor function. A dose-response study (25, 50, 100, 200 μmol/kg) was performed to ascertain the effect of MD treatment on injured animals comparing to uninjured controls and injured animals treated with the vehicle (saline). We found that BB performance improved to control levels after MD treatment at 25 μmol/kg and 50 μmol/kg whereas animals treated with saline did not improve. SLA and SAB performance did not improve after treatment with MD. The findings suggest that HO-2 activation may be a viable method in mitigating further injury after TBI. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2014-06-27 19:33:45.645

No description available.

This study examined the effects of bilateral and unilateral deafness by measuring cortical auditory evoked potential (CAEP) responses in children at initial stages of bilateral cochlear implant (CI) use. We recorded cortical responses evoked by right and left CI stimulation in 127 children with early onset (< 12 months) deafness, with 72 children receiving the two devices in the same surgery (simultaneously implanted) and 55 children receiving the devices in separate procedures (sequentially implanted). Three different types of responses were identified in children with bilateral CIs. No significant effects of duration of deafness, age at implantation, or duration of unilateral CI use were found on response latencies and amplitudes within each type of cortical response, but there were clear differences in responses types between groups and ears. In the context of these findings, the effects of bilateral and unilateral deafness to the auditory pathways were discussed.

Deafness in early development can alter how the brain responds to sound, compromising the restoration of hearing with cochlear implants. We asked how the naïve brain responds to initial cochlear implant stimulation in children who are deaf. Results indicated large variability in initial responses. Deafness associated with GJB-2 mutations led to more uniformity in cortical responses than other etiologies. Responses associated with GJB-2 mutations were characterized by a response peak with large contributions from temporal and frontal regions of the brain. This response may reflect an early stage of auditory development. By contrast, another response type, typical of normal hearing children, received less contribution from frontal regions. Through consistent cochlear implant use, frontal regions of the brain may not be as strongly recruited. Effects of deafness in early development are heterogeneous, which may reflect differences in etiology of deafness and different stages of auditory development.

This study examined the effects of bilateral and unilateral deafness by measuring cortical auditory evoked potential (CAEP) responses in children at initial stages of bilateral cochlear implant (CI) use. We recorded cortical responses evoked by right and left CI stimulation in 127 children with early onset (< 12 months) deafness, with 72 children receiving the two devices in the same surgery (simultaneously implanted) and 55 children receiving the devices in separate procedures (sequentially implanted). Three different types of responses were identified in children with bilateral CIs. No significant effects of duration of deafness, age at implantation, or duration of unilateral CI use were found on response latencies and amplitudes within each type of cortical response, but there were clear differences in responses types between groups and ears. In the context of these findings, the effects of bilateral and unilateral deafness to the auditory pathways were discussed.