Regulation of hippocampal synaptic function by the metabolic hormone, leptin:Implications for health and neurodegenerative disease

The role of the endocrine hormone leptin in controlling energy homeostasis in the hypothalamus are well documented. However the CNS targets for leptin are not restricted to the hypothalamus as a high density of leptin receptors are also expressed in several parts of the brain involved in higher cognitive functions including the hippocampus. Numerous studies have identified that in the hippocampus, leptin has cognitive enhancing actions as exogenous application of this hormone facilitates hippocampal-dependent learning and memory, whereas lack or insensitivity to leptin results in significant memory deficits. Leptin also markedly influences some of the main cellular changes that are involved in learning and memory including NMDA-receptor dependent synaptic plasticity and glutamate receptor trafficking. Like other metabolic hormones, there is a significant decline in neuronal sensitivity to leptin during the ageing process. Indeed, the capacity of leptin to modulate the functioning of hippocampal synapses is substantially reduced in aged compared to adult tissue. Clinical studies have also identified an association between circulating leptin levels and the risk of certain neurodegenerative disorders such as Alzheimer’s disease (AD). In view of this, targeting leptin and/or its receptor/signaling mechanisms may be an innovative approach for developing therapies to treat AD. In support of this, accumulating evidence indicates that leptin has cognitive enhancing and neuroprotective actions in various models of AD. Here we assess recent evidence that supports an important regulatory role for leptin at hippocampal CA1 synapses, and we discuss how age-related alterations in this hormonal system influences neurodegenerative disease

Right-lateralised lane keeping in young and older British drivers

Young adults demonstrate a small, but consistent, asymmetry of spatial attention favouring the left side of space (“pseudoneglect”) in laboratory-based tests of perception. Conversely, in more naturalistic environments, behavioural errors towards the right side of space are often observed. In the older population, spatial attention asymmetries are generally diminished, or even reversed to favour the right side of space, but much of this evidence has been gained from lab-based and/or psychophysical testing. In this study we assessed whether spatial biases can be elicited during a simulated driving task, and secondly whether these biases also shift with age, in line with standard lab-based measures. Data from 77 right-handed adults with full UK driving licences (i.e. prior experience of left-lane driving) were analysed: 38 young (mean age = 21.53) and 39 older adults (mean age = 70.38). Each participant undertook 3 tests of visuospatial attention: the landmark task, line bisection task, and a simulated lane-keeping task. We found leftward biases in young adults for the landmark and line bisection tasks, indicative of pseudoneglect, and a mean lane position towards the right of centre. In young adults the leftward landmark task biases were negatively correlated with rightward lane-keeping biases, hinting that a common property of the spatial attention networks may have influenced both tasks. As predicted, older adults showed no group-level spatial asymmetry on the landmark nor the line bisection task, but they maintained a mean rightward lane position, similar to young adults. The 3 tasks were not inter-correlated in the older group. These results suggest that spatial biases in older adults may be elicited more effectively in experiments involving complex behaviour rather than abstract, lab-based measures. More broadly, these results confirm that lateral biases of spatial attention are linked to driving behaviour, and this could prove informative in the development of future vehicle safety and driving technology

Animating evaluation: A multimodal appraisal analysis of story-time animation

This dissertation presents the multimodal appraisal analysis of story-time animation videos; a form of computer-mediated motion picture entertainment that are conventionally uploaded to the social media platform YouTube. By means of the multimodal appraisal analysis, this dissertation aims to elucidate the potential of story-time animation to construe emotions and opinions. To achieve this goal, the dissertation establishes a multimodal appraisal methodology which facilitates the identification, description and analysis of emotions and opinions in texts which implement several communicative modes. The dissertation first outlines several linguistic frameworks constructed to identify emotions and opinions - such as Martin and White’s Appraisal Framework (2005) - and proceeds to explore how such frameworks have been adapted to identify emotions and opinions in multimodal texts. It then establishes the multimodal appraisal methodology established in this dissertation, designed specifically with animated media in mind. The dissertation then applies this multimodal appraisal framework to various scenes of three story-time animation videos produced by the YouTube content creator ‘Jaiden Animations’ in order to elucidate the evaluative potential of story-time animations. The multimodal appraisal analysis of this dissertation ascertained that story-time animations possess great potential to construe emotion and opinions however each of the communicative modes that it utilises commits to these emotions and opinions to varying degrees. It also observed that these communicative modes would complement and contradict one another in order to upscale and downscale emotions and opinions and to construe a wide range of emotion hybrids

Characterising physical habitat at the reach scale: River Tern, Shropshire

Characterisation of the complex geomorphological and ecological structure of river channels into workable units of instream habitat is a key step in enabling the assessment of habitat for river management purposes. The research presented in this thesis uses a range of methodological approaches at a variety of spatial scales in order to improve the conceptual basis of habitat characterisation at the reach and sub-reach scale. An appraisal of published works is used in conjunction with an extensive analysis of habitat features for sites across the UK, and intensive field studies on the River Tern, Shropshire, to improve the conceptual basis and ecological validity of the 'physical biotope' as the basic unit of instream habitat. Physical biotopes demonstrate correlations with biologically functional habitat units at relatively broad scales, suggesting that assemblages of habitat units may provide the most appropriate level of simplification of aquatic habitat structure. A simplified, but more transferable classification using biotope assemblages is suggested, with potential application to a range of instream assessment and river design needs. Reach-scale field surveys reveal complex and dynamic relationships between channel hydraulics and morphology and highlight the influence of sampling design and hydrological context on the outcomes of rapid field surveys. A microscale research component addresses within-biotope variation at small scales by focusing on high frequency flow behaviour and sediment transport mechanisms which have, to date, been largely overlooked in biotope studies. This provides both detailed descriptions of hydraulic behaviour, and an indication of differences in internal spatial and temporal heterogeneity between biotopes, with implications for instream biota

Intra- and inter-task reliability of spatial attention measures in healthy older adults

At present, there is a lack of systematic investigation into intra- and inter-task consistency effects in older adults, when investigating lateralised spatial attention. In young adults, spatial attention typically manifests itself in a processing advantage for the left side of space (“pseudoneglect”), whereas older adults have been reported to display no strongly lateralised bias, or a preference towards the right side. Building on our earlier study in young adults, we investigated older adults, aged between 60 to 86 years, on five commonly used spatial attention tasks (line bisection, landmark, grey and grating scales and lateralised visual detection). Results confirmed a stable test-retest reliability for each of the five spatial tasks across two testing days. However, contrary to our expectations of a consistent lack in bias or a rightward bias, two tasks elicited significant left spatial biases in our sample of older participants, in accordance with pseudoneglect (namely the line bisection and greyscales tasks), while the other three tasks (landmark, grating scales, and lateralised visual detection tasks) showed no significant biases to either side of space. This lack of inter-task correlations replicates recent findings in young adults. Comparing the two age groups revealed that only the landmark task was age sensitive, with a leftward bias in young adults and an eliminated bias in older adults. In view of these findings of no significant inter-task correlations, as well as the inconsistent directions of the observed spatial biases for the older adults across the five tested tasks, we argue that pseudoneglect is a multi-component phenomenon and highly task sensitive. Each task may engage slightly distinct neural mechanisms, likely to be impacted differently by age. This complicates generalisation and comparability of pseudoneglect effects across different tasks, age-groups and hence studies

Characterising physical habitat at the reach scale: River Tern, Shropshire

Characterisation of the complex geomorphological and ecological structure of river channels into workable units of instream habitat is a key step in enabling the assessment of habitat for river management purposes. The research presented in this thesis uses a range of methodological approaches at a variety of spatial scales in order to improve the conceptual basis of habitat characterisation at the reach and sub-reach scale. An appraisal of published works is used in conjunction with an extensive analysis of habitat features for sites across the UK, and intensive field studies on the River Tern, Shropshire, to improve the conceptual basis and ecological validity of the 'physical biotope' as the basic unit of instream habitat. Physical biotopes demonstrate correlations with biologically functional habitat units at relatively broad scales, suggesting that assemblages of habitat units may provide the most appropriate level of simplification of aquatic habitat structure. A simplified, but more transferable classification using biotope assemblages is suggested, with potential application to a range of instream assessment and river design needs. Reach-scale field surveys reveal complex and dynamic relationships between channel hydraulics and morphology and highlight the influence of sampling design and hydrological context on the outcomes of rapid field surveys. A microscale research component addresses within-biotope variation at small scales by focusing on high frequency flow behaviour and sediment transport mechanisms which have, to date, been largely overlooked in biotope studies. This provides both detailed descriptions of hydraulic behaviour, and an indication of differences in internal spatial and temporal heterogeneity between biotopes, with implications for instream biota

Correction: Intra- and inter-task reliability of spatial attention measures in pseudoneglect

No abstract available

Re-introduction of structurally complex wood jams promotes channel and habitat recovery from overwidening: Implications for river conservation

Copyright © 2017 John Wiley & Sons, Ltd. Large wood is a powerful geomorphic agent in rivers, providing important habitat functions for a range of aquatic organisms, but has been subject to a long history of removal. Internationally, approaches to river restoration are increasingly incorporating large wood features, but generally favour simple flow deflectors (e.g. single logs, stripped of branches and anchored in place) over more complex structures that more accurately mimic natural wood jams. This paper explores channel response to wood-based restoration of an overwidened lowland chalk stream that incorporated whole felled trees. Hydraulics, sediment, topography and vegetation data were assessed for a 3year period for two restored reaches: an upstream reach where pre-restoration baseline data were obtained, and a downstream reach restored before data collection. Where pre-restoration data were available, the introduction of wood jams generated sediment deposition within jams leading to the development of vegetated marginal ‘benches’ and bed scour in adjacent areas of flow convergence. Patterns were less clear in the downstream reach, where restoration design was less ambitious and outcomes may have been affected by subsequent restoration work upstream. The results indicate that reintroduction of large wood (whole trees), can promote channel and habitat recovery from overwidening in lowland rivers, creating important ecological benefits through the provision of structurally complex marginal habitat and associated food resources. Longer-term assessments are required to establish whether the trajectories of change are persistent. The work emphasizes the effectiveness of restoration approaches that aim to ‘work with nature’. The ambitious design, incorporating structurally complex wood jams, was also low-cost, using materials available from the river corridor (existing riparian trees). Furthermore, ecosystem engineering effects were amplified by the colonization of wood jams by aquatic vegetation. The approach should, therefore, be transferable to other lowland rivers, subject to wider catchment constraints