The role of the dentate gyrus and adult neurogenesis in hippocampal-basal ganglia associated behaviour

The ability of the brain to continually generate new neurons throughout life is one of the most intensely researched areas of modern neuroscience. While great advancements in understanding the biochemical mechanisms of adult neurogenesis have been made, there remain significant obstacles and gaps in connecting neurogenesis with behavioural and cognitive processes such as learning and memory. The purpose of the thesis was to examine by review and laboratory experimentation the role of the dentate gyrus and of adult neurogenesis within the hippocampus in the performance of cognitive tasks dependent on the hippocampal formation and hippocampal-basal ganglia interactions. Advancement in understanding the role of neurogenesis in these processes may assist in improving treatments for common brain injury and cognitive diseases that affect this region of the brain. Mild chronic stress reduced the acquisition rate of a stimulus-response task (p=0.043), but facilitated the acquisition of a discrimination between a small and a large reward (p=0.027). In locomotor activity assays, chronic stress did not shift the dose-response to methamphetamine. Analysis of 2,5-bromodeoxyuridine incorporation showed that, overall, chronic mild stress did not effect survival of neuronal progenitors . However, learning of the tasks had a positive influence on cell survival in stressed animals (p=0.038). Microinjections of colchicine produced significant lesions of the dentate gyrus and surrounding CA1-CA3 and neocortex. Damage to these regions impaired hippocampal-dependent reference memory (p=0.054) while preserving hippocampal independent simple discrimination learning. In a delay discounting procedure, the lesions did not induce impulsive-like behaviour when delay associated with a large reward was introduced. The experiments uphold a current theory that learning acts as a buffer to mitigate the negative effects of stress on neurogenesis

Complex double-binary-offset-carrier modulation for a unitary characterisation of Galileo and GPS signals

In this paper we introduce a new class of modulations, the Complex Double Binary-Carrier-Offset (CDBOC) modulation class, which covers most of the modulation types proposed so far for Galileo and GPS signals, namely the binary and quaternary phase shift keying (BPSK/QPSK), sine BOC (SinBOC), cosine BOC (CosBOC) and alternate BOC (AltBOC) modulations. At the same time, CDBOC class provides a more general framework, with potential for new applications of wide-band CDMA systems and/or future satellite navigation systems. We introduce the theoretical derivations of the Power Spectral Density (PSD) and the Auto-Correlation Function (ACF) of the CDBOC-modulated signals, and we compare the theoretical analysis with the results obtained via simulations. The advantage of our method in the context of Galileo and GPS signals is its simplicity and the fact that it provides unified analytical formulas for most of the existent GPS/Galileo signals.Peer reviewe

Subchip Multipath Delay Estimation for Downlink WCDMA System Based on Teager-Kaiser Operator

Accurate detection and estimation of overlapping fading multipath components is vital for many communication systems, particularly for positioning technologies. Traditional approaches used for channel estimation generally fail in estimating closely-spaced multipath components in CDMA systems. Here, we present a highly efficient technique for asynchronous downlink WCDMA multipath delay estimation with subchip resolution capability based on nonlinear Teager-Kaiser operator concept. The behaviour of this technique is influenced considerably by the pulse shape waveform. Both rectangular and root raised cosine pulse shaping filters are considered.Peer reviewe