This thesis derives a new learning system which is presented as both an improved cerebellar model and as a general purpose learning machine. It is based on a summary of recent publications concerning the operating characteristics and structure of the mammalian cerebellum and on standard interpolating and surface fitting techniques for functions of one and several variables. The system approximates functions as weighted sums of continuous basis functions. Learning, which takes place in an iterative manner, is accomplished by presenting the system with arbitrary training points (function input variables) and associated function values. The system is shown to be capable of minimizing the estimation error in the mean-square-error sense. The system is also shown to minimize the expectation of the interference, which results from learning at a single point, on all other points in the input space. In this sense, the system maximizes the rate at which arbitrary functions are learned. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Unknown

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

No description available.

No description available.

Mutations of the α1A subunit of CaV 2.1 voltage gated calcium (VGCC) channels are responsible for several inherited disorders affecting humans, including familial hemiplegic migraine, episodic ataxia type and spinocerebellar ataxia type. The leaner mouse also carries an autosomal recessive mutation in the α1A subunit of CaV 2.1 VGCCs, which, in the homozygous condition, results in a severe cerebellar atrophy and ataxia. The leaner mutation results in reduced calcium influx through CaV 2.1 VGCCs. To better understand cerebellar neurodegeneration and cerebellar dysfunction we focused our research on elucidating the relationship between mitochondrial function/dysfunction and calcium channel mutations. The aims of this dissertation were: 1) to estimate the extent of neuronal cell death, basal intracellular calcium and mitochondrial (dys)function in cerebellar granule cells (CGC) of adult leaner mice; 2) to analyze the role of the leaner calcium channel mutation on postnatal development of CGCs; and 3) to test whether inducing increased calcium influx by exposing cultured granule cells to potassium chloride can eliminate or reduce the CGC death. By using mechanism independent Fluoro-Jade staining and apoptosis specific TUNEL staining, we demonstrated that leaner CGC death continues into adulthood and the spatial pattern of granule cell death observed during postnatal development also continues into adulthood. The present investigation showed a reduced resting intracellular calcium in CGC from leaner mice as compared to age matched wild type mice, and tottering mice. The tottering mouse is another mutant mouse that carries a mutation in the α1A subunit of CaV 2.1 VGCCs like leaner mouse. However, these mice do not show any neurodegeneration and therefore they were used as a second control. Our results also showed that even though CGC of leaner mice have dysfunctional CaV2.1 channels, there is no change in depolarization induced Ca2+ influx, which suggests a functional compensation for CaV2.1 calcium channels by other VGCCs. Our results showed reduced mitochondrial membrane potential at the time of peak CGC death in leaner mice as compared to wild type CGCs and tottering CGCs. The results of this investigation suggest mitochondrial mediated but reactive oxygen species independent cell death in CGCs of leaner mice.

The cerebellum is a region of the brain responsible for an organism’s ability to perform precise, coordinated movements. An abundance of research has characterized the anatomy of the cerebellum, and provides the foundation of current theories regarding the circuitry that supports motor learning. Delay eyelid conditioning is a form of motor learning. It is the learned association of a neutral stimulus and the reflexive response of an eyelid closure resulting in a well-timed eyelid closure in anticipation of the reflexive response. Two aspects of this learning are: different-conditioned stimulus savings and savings of timing. Different-CS savings is a rapid re-learning to a new, different neutral stimulus that occurs more quickly than learning to the original stimulus. Savings of timing is a phenomenon in which the timing of a response is preserved from a prior training experience. This dissertation presents evidence that forebrain input to the cerebellum is required for these aspects of delay eyelid conditioning. We trained animals with electrical stimulation as our neutral stimulus and thereby engaged a specific input pathway to the cerebellum, limiting forebrain inputs. In Chapter 2 we implement this technique and eliminate different-CS savings. These data suggest that forebrain input mediates this phenomenon. We then proceeded to investigate if the prefrontal cortex (PFC) is the forebrain region involved in supporting this aspect of delay eyelid conditioning. We administered electrolytic lesions to the PFC of animals and found their ability to express different-CS savings was impaired. Evidence from these two chapters suggests the PFC provides input to the cerebellum necessary for different-CS savings. Finally, in Chapter 4 we examine savings of timing. We again limit forebrain input to the cerebellum and implement electrical stimulation as our neutral training stimulus. With stimulation as the neutral stimulus, animals do not exhibit savings of timing. The data suggest that a forebrain region is necessary to sustain this phenomenon as well. This dissertation provides two lines of evidence strongly supporting forebrain involvement in these modifications of delay eyelid conditioning - savings and savings of timing. These results convey the importance of accommodating forebrain-cerebellum interactions when developing theories of cerebellar function. / text

About 400 million years ago sharks developed a separate co-processor in their brains that not only made them faster but also more precisely coordinated. This co-processor, which is nowadays called cerebellum, allowed sharks to outperform their peers and survive as one of the fittest. For the last 40 years or so, researchers have been attempting to provide robots and other machines with this type of capability. This thesis discusses currently used methods to create artificial cerebellums and points out two main shortcomings: 1) framework usability issues and 2) building blocks incompatibility issues. This research argues that the framework usability issues hinder the production of good quality artificial cerebellums for a large number of applications. Furthermore, this study argues that the building blocks incompatibility issues make artificial cerebellums less efficient that they could be, given our current technology. To tackle the framework usability issues, this thesis research proposes the use of a new framework, which formalizes the task of creating artificial cerebellums and offers a list of simple steps to accomplish this task. Furthermore, to tackle the building blocks incompatibility issues, this research proposes thinking of artificial cerebellums as a set of cooperating q-learning agents, which utilize a new technique called Moving Prototypes to make better use of the available memory and computational resources. Furthermore, this work describes a set of general guidelines that can be applied to accelerate the training of this type of system. Simulation is used to show examples of the performance improvements resulting from the use of these guidelines. To illustrate the theory developed in this dissertation, this paper implements a cerebellum for a real life application, namely, a cerebellum capable of controlling a type of mining equipment called front-end loader. Finally, this thesis proposes the creation of a development tool based on this formalization. This research argues that such a development tool would allow engineers, scientists and technicians to quickly build customized cerebellums for a wide range of applications without the need of becoming experts on the area of Artificial Intelligence, Neuroscience or Machine Learning.

Over two decades of patient and neuroimaging data have provided increasing support for a role of the posterior cerebellum in cognition, particularly attention. Contralateral connections between the prefrontal cortex and the cerebellum are a probable basis for this effect. It is the purpose of this thesis to understand the contribution of the fronto-cerebellar system to cognitive and attentional processes. The first aim of this thesis was to localize areas of the cerebellum that participate in non-motor behaviour. After transient disruption of cerebellar activity using continuous theta burst stimulation (cTBS), a form of transcranial magnetic stimulation, Study 1 and 2 identified the right posterior-lateral cerebellum as a contributor to a network involved in two non-motor tasks; word generation and the attentional blink. The aim of Study 3 was to investigate if manipulating task demands increased fronto-cerebellar recruitment. The final study of this thesis employed electroencephalography (EEG) and cTBS to probe the neural events disrupted during the attentional blink task when the left frontal- right cerebellar system was transiently disrupted. Understanding the manner in which these neural events are affected by transient perturbation is integral to the understanding of the fronto-cerebellar contribution to cognitive and attentional processes. Together these studies help elucidate the role of the fronto-cerebellar system in non-motor functions.

Over two decades of patient and neuroimaging data have provided increasing support for a role of the posterior cerebellum in cognition, particularly attention. Contralateral connections between the prefrontal cortex and the cerebellum are a probable basis for this effect. It is the purpose of this thesis to understand the contribution of the fronto-cerebellar system to cognitive and attentional processes. The first aim of this thesis was to localize areas of the cerebellum that participate in non-motor behaviour. After transient disruption of cerebellar activity using continuous theta burst stimulation (cTBS), a form of transcranial magnetic stimulation, Study 1 and 2 identified the right posterior-lateral cerebellum as a contributor to a network involved in two non-motor tasks; word generation and the attentional blink. The aim of Study 3 was to investigate if manipulating task demands increased fronto-cerebellar recruitment. The final study of this thesis employed electroencephalography (EEG) and cTBS to probe the neural events disrupted during the attentional blink task when the left frontal- right cerebellar system was transiently disrupted. Understanding the manner in which these neural events are affected by transient perturbation is integral to the understanding of the fronto-cerebellar contribution to cognitive and attentional processes. Together these studies help elucidate the role of the fronto-cerebellar system in non-motor functions.