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Biomedical subjects

Barbara Webb

Publications and source records attributed to Barbara Webb.

10 recordsLinked to original sources
PubMed2006

Directional hearing in a silicon cricket.

Phonotaxis is the ability to orient towards or away from sound sources. Crickets can locate conspecifics by phonotaxis to the calling (mating) song they produce, and can evade bats by negative phonotaxis from echolocation calls. The behaviour and underlying physiology have been studied in some depth, and the auditory system solves this complex problem in a unique manner. Experiments conducted on a simulation model of the system indicated that the mechanism output a directional signal to sounds ahead at calling song frequency and to sounds behind at echolocation frequencies. We suggest that this combination of responses helps simplify later processing in the cricket. To further explore this result, an analogue, very large scale integrated (aVLSI) circuit model of the mechanism was designed and built; results from testing this agreed with the simulation. The aVLSI circuit was used to test a further hypothesis about the potential advantages of the positioning of the acoustic inputs for sound localisation during walking. There was no clear advantage to the directionality of the system in their location. The aVLSI circuitry is now being extended to use on a robot along with previously modelled neural circuitry to better understand the complete sensorimotor pathway.

Animals↗
PubMed2006

Validating biorobotic models.

Some issues in neuroscience can be addressed by building robot models of biological sensorimotor systems. What we can conclude from building models or simulations, however, is determined by a number of factors in addition to the central hypothesis we intend to test. These include the way in which the hypothesis is represented and implemented in simulation, how the simulation output is interpreted, how it is compared to the behaviour of the biological system, and the conditions under which it is tested. These issues will be illustrated by discussing a series of robot models of cricket phonotaxis behaviour.

Animals↗
PubMed2006

A cadaveric investigation into the links between macroscopic and microscopic osteoarthritic changes at the hip.

Our objective was to investigate the frequency and distribution of osteoarthritic changes at the hip, including the relationship between osteoarthritic lesions on the femoral head surface and histological changes in articular cartilage, in 12 cadavers. Twelve embalmed cadavers (five males and seven females) were dissected, and the femoral head was removed from both sides (24 femoral heads). Any gross osteoarthritic changes were noted and graded (on a scale of 1-3). A circular disc was then removed from the equator of the femoral head and divided into nine regions. Out of 192 segments, 54 underwent sectioning and staining with haematoxylin and eosin to assess histological changes in cartilage. Osteoarthritis of the hip was present in all cadavers, with all males having bilateral OA and 50% having grade 2 or higher lesions (50% were grade 1), and four of the seven female specimens having bilateral OA and only 7% with grade 2 lesions (with 71% grade 1 and 21% normal). Chondrocyte clustering was most commonly observed in the deep layer of cartilage followed by the intermediate and superficial layers respectively, as the grade of the macroscopic lesion increased. Cartilage injury at the histological level precedes any visible denudation of the femoral head articular cartilage. This study supports the hypothesis that early osteoarthritic changes occur in the deep layer of cartilage near the tide mark and progress superficially concomitant with an overall increase in the osteoarthritic lesion size on the femoral head surface.

Aged↗
PubMed2004

Neural mechanisms for prediction: do insects have forward models?

'Forward models' are increasingly recognized as a crucial explanatory concept in vertebrate motor control. The essential idea is that an important function implemented by nervous systems is prediction of the sensory consequences of action. This is often associated with higher cognitive capabilities; however, many of the purposes forward models are thought to have analogues in insect behaviour, and the concept is closely connected to those of 'efference copy' and 'corollary discharge'. This article considers recent evidence from invertebrates that demonstrates the predictive modulation of sensory processes by motor output, and discusses to what extent this supports the conclusion that insect nervous systems also implement forward models. Several promising directions for further research are outlined.

Animals↗
PubMed2003

Nerve growth factor and chronic ethanol treatment alter calcium homeostasis in developing rat septal neurons.

Chronic ethanol treatment (CET) during development produces cellular adaptations resulting in tolerance to the acute effects of ethanol (EtOH). The objectives of this study were to determine whether CET during the prenatal period (PCET) followed by a period of in vitro CET (PCET-CET) altered intracellular calcium [Ca(2+)](i) and produced tolerance to acute EtOH treatment (AET), and whether nerve growth factor (NGF) modulated the effects of PCET-CET in cultured developing rat septal neurons. Fetuses were obtained from EtOH-fed and sucrose-fed (diet-control) female rats. Neurons from PCET fetuses were cultured in the presence of NGF (+NGF) and 200 mg/dl (mg %) EtOH and diet-control cultures received NGF and no EtOH. PCET and diet-control cultures were then divided into two groups, +NGF and -NGF (withdrawn from NGF), and exposed acutely to one of five doses of EtOH during stimulation with potassium (K(+)) chloride. [Ca(2+)](i) was measured using fura-2. PCET-CET did not affect resting [Ca(2+)](i). PCET-CET decreased and acute EtOH withdrawal increased overall K(+)-stimulated changes in [Ca(2+)](i), but only in +NGF PCET neurons. Reducing the level of EtOH from 200 to 100 mg % decreased overall K(+)-stimulated [Ca(2+)](i) in -NGF PCET neurons. The effects of PCET-CET or PCET-CET combined with NGF on overall K(+)-stimulated changes in [Ca(2+)](i) occurred mostly in the early and middle phases of the K(+)-response. NGF reduced overall K(+)-stimulated changes in [Ca(2+)](i) in PCET neurons during EtOH withdrawal and during AET with 200 mg % EtOH and increased overall K(+)-stimulated changes in [Ca(2+)](i) during AET with 400 and 800 mg % EtOH. There was no effect of NGF on overall K(+)-stimulated changes in [Ca(2+)](i) in diet-control neurons with the exception that NGF-treatment decreased overall K(+)-stimulated changes in [Ca(2+)](i) during AET with 400 mg % EtOH. The effects of AET on overall K(+)-stimulated changes in [Ca(2+)](i) mostly occurred in +NGF PCET neurons. In conclusion, CET during development of the brain could adversely affect Ca(2+)-dependent functions such as neuronal migration, neurite outgrowth, and synaptogenesis in neurons even in the presence of neurotrophin support.

Animals↗
PubMed2002

Robots in invertebrate neuroscience.

Can we now build artificial animals? A combination of robot technology and neuroethological knowledge is enabling the development of realistic physical models of biological systems. And such systems are not only of interest to engineers. By exploring identified neural control circuits in the appropriate functional and environmental context, new insights are also provided to biologists.

Animals↗
PubMed2002

Using focus groups as a research method: a personal experience.

AIM: The personal experience and systematic process of using focus groups as a research method to assist change within an NHS Trust are described. BACKGROUND: Focus groups have recently emerged as a popular qualitative research method in health research and were used in a qualitative research study to explore, from an Enrolled Nurse perspective, what it was that prevented them coming forward for conversion to the First Level of the UKCC Nursing Register. METHOD: The author facilitated the five focus groups with Enrolled Nurse membership within the local organizational context. Data were recorded on audio-tapes and transcribed in preparation for analysis. RESULTS: The use of focus groups in health care research has key benefits for involving people in the research process and the subsequent changes that may occur as a result. The use of focus groups presented real challenges in the area of recruiting Enrolled Nurses to engage in such a process. CONCLUSIONS: Focus groups have a valuable role to play in both research and the involvement of people in organizational change and development. However, to persuade traditionally disempowered groups to engage in the process will be a challenge to the leaders of such projects.

Female↗
PubMed2002

Sex differences in ethanol-induced hypnosis and hypothermia in young Long-Evans rats.

INTRODUCTION: Females experience greater liver damage, have reduced brain size, and have greater memory deficits than do males with a similar history of alcoholism. Females have higher peak alcohol levels and faster elimination rates than males. Our goal was to study sex differences in the response of young ethanol-naïve outbred Long-Evans rats to acute ethanol exposure so that we may better understand why females are more sensitive to alcohol toxicity than males. METHODS: Females aged 49 days and males aged 43 days, weighing 153.6 and 177.5 g, respectively, were tested for their initial response to ethanol. Fasted (12 hr) females (in diestrous) and males were given an intraperitoneal injection of 3.0 g/kg of ethanol (v/v in 0.9% sterile saline). Body temperature, loss of the righting reflex (LORR), return of the righting reflex, and tail blood alcohol concentration (BAC) were monitored. RESULTS: LORR occurred at the same time in females and males. The return of the righting reflex occurred later in males than in females. BACs were the same in the males and females except at LORR, when BAC was lower in the males. Acute ethanol tolerance developed in more males than females. Females demonstrated a slower recovery from peak ethanol-induced hypothermia than males. The proportions of lean body mass, ethanol elimination, and ethanol metabolism were similar in the females and males. CONCLUSIONS: Ethanol-naïve young male and female Long-Evans rats demonstrated sex differences in their initial responses to ethanol. Males were more sensitive than females to the hypnotic effect of ethanol, whereas females were more sensitive than males to ethanol-induced hypothermia. In addition, more males than females developed acute ethanol tolerance. Investigating the mechanisms underlying these differences may help us to understand why females experience more of the adverse effects of alcohol consumption than males.

Aging↗
PubMed1998

Robots, crickets and ants: models of neural control of chemotaxis and phonotaxis.

Neural control in animals can be investigated using robot models. Two simple behaviours are focused on: pheromone trail following in ants and sound source localization in crickets. Our models address the real sensorimotor constraints and physiological underpinnings of these behaviours. Using alcohol gas sensors on a robot it is shown that a simple neural architecture can reproduce a range of trail-following behaviours that qualitatively resemble the results reported for ants. Building a more detailed auditory sensor based on the cricket ear it is shown that preference for song frequency and pattern does not require a recognition mechanism, using real cricket song as stimuli. Finally the spiking neuron models that enable us to examine exactly how these robust forms of motor control can emerge from small networks of neurons are introduced.

Journal Article↗