title: Native bird abundance after Australian magpie (Gymnorhina tibicen) removal from localised areas of high resource availability

authors: Morgan, Dai K.J.

subjects: bird monitoring

abstract: Many reports exist of Australian magpies (Gymnorhina tibicen) attacking and sometimes killing other birds. One study concluded that magpies had little impact on the abundance of other birds at landscape scales, but another found that birds (mainly exotic species) avoided flying or landing close to them. We assessed whether continuously removing magpies for 6 weeks from localised areas of high resource availability (e.g. bush remnants or private gardens with fruit- or nectar-producing trees) in rural areas increased visitations by native birds compared with similar sites where magpies were not removed. Three count methods were used to estimate bird abundance: five-minute bird counts and ‘slow-walk’ transects in bush remnants, and five-minute bird counts and ‘snapshot’ counts in gardens. Generally, the abundance of native birds did not increase in treatment areas after magpie removal. In bush remnants, transect counts were typically better at detecting the presence of most species compared with five-minute bird counts. In gardens, snapshot counts were better at detecting tui (Prosthemadera novaeseelandiae) while five-minute bird counts were better at detecting magpies. Despite these differences, the different bird counting methods were generally in agreement and revealed that magpies had little impact on native birds at the scale we examined.

text: Native bird abundance after Australian magpie (Gymnorhina tibicen) removal from localised areas of high resource availability Many reports exist of Australian magpies (Gymnorhina tibicen) attacking and sometimes killing other birds. One study concluded that magpies had little impact on the abundance of other birds at landscape scales, but another found that birds (mainly exotic species) avoided flying or landing close to them. We assessed whether continuously removing magpies for 6 weeks from localised areas of high resource availability (e.g. bush remnants or private gardens with fruit- or nectar-producing trees) in rural areas increased visitations by native birds compared with similar sites where magpies were not removed. Three count methods were used to estimate bird abundance: five-minute bird counts and ‘slow-walk’ transects in bush remnants, and five-minute bird counts and ‘snapshot’ counts in gardens. Generally, the abundance of native birds did not increase in treatment areas after magpie removal. In bush remnants, transect counts were typically better at detecting the presence of most species compared with five-minute bird counts. In gardens, snapshot counts were better at detecting tui (Prosthemadera novaeseelandiae) while five-minute bird counts were better at detecting magpies. Despite these differences, the different bird counting methods were generally in agreement and revealed that magpies had little impact on native birds at the scale we examined.

year: 2012

title: Theoretical and experimental investigation of anaesthetic effects in the brain

authors: Noroozbabaee, Leyla

abstract: The main motivation of this study is to develop a better understanding of anaesthetic drug effects on brain dynamics including the paradoxical enhancement of seizure activity by some anaesthetic drugs. This thesis investigates two mean-field descriptions for the effect of general anaesthetic agents on brain activity: the extended Waikato cortical model (WM) and the Hindriks and van Putten (HvP) thalamocortical model. In the standard Waikato model, the population-average neuron voltage is determined by incoming activity at both electrical (gap-junction) and chemical synapses, the latter mediated by AMPA (excitatory) and GABAA (inhibitory) receptors. Here we extend the standard WM by including NMDA (excitatory) and GABAB (inhibitory) synapses. GABAergic anaesthetics, such as propofol, boost cortical inhibition by prolonging the tail of the unitary IPSP (inhibitory postsynaptic potential) at GABAA receptors, while increasing the synaptic gain at the slower-acting GABAB receptors. Dissociative anaesthetics act on NMDA receptors to give a voltage-dependent alteration of excitatory synaptic gain. We find that increasing GABAB or NMDA effect can alter the spatiotemporal dynamics of the standard WM, tending to suppress spatial (Turing) patterns in favour of temporal (Hopf) oscillations. The extended WM predicts increased susceptibility to seizure when GABAB effect is increased, particularly if the GABAergic agent reduces gap-junction diffusion. 
We tested these WM predictions with two biological experiments. We found that potentiation of GABAB receptors in slices of mouse cortical tissue tended to enhance seizure-like activity. However, our in vivo investigation of the effect of closure of gap junctions did not reveal any seizure patterns in mouse EEG signals. 
In the second part of this thesis, we present a detailed analysis of the HvP thalamocortical mean-field model for propofol anaesthesia. While we were able to confirm the Hindriks and van Putten predictions of increases in delta and alpha power at low levels of anaesthetic sedation, we find that for deeper anaesthetic effect, the model jumps from the low-firing state to an extremely high-firing stable state (~250 spikes/s), and remains stuck there even at GABAA prolongations as high as 300% which would be expected to induce full comatose suppression of all firing activity. To overcome this pathological behaviour, we tested two possible modifications: first, eliminating the population-dependent anaesthetic sensitivity (efficacy) of the HvP model; second, incorporating reversal potentials and tuning the excitatory sigmoid parameters defining the mapping from voltage to firing rate. The first modification removes the pathological state, but predicts de-creasing alpha and delta power as drug concentration increases. The second modification predicts induction-emergence hysteresis (drug concentration is higher at induction than at emergence), but the alpha rhythm is lost, being replaced by a dominant delta-band oscillation.

text: Theoretical and experimental investigation of anaesthetic effects in the brain The main motivation of this study is to develop a better understanding of anaesthetic drug effects on brain dynamics including the paradoxical enhancement of seizure activity by some anaesthetic drugs. This thesis investigates two mean-field descriptions for the effect of general anaesthetic agents on brain activity: the extended Waikato cortical model (WM) and the Hindriks and van Putten (HvP) thalamocortical model. In the standard Waikato model, the population-average neuron voltage is determined by incoming activity at both electrical (gap-junction) and chemical synapses, the latter mediated by AMPA (excitatory) and GABAA (inhibitory) receptors. Here we extend the standard WM by including NMDA (excitatory) and GABAB (inhibitory) synapses. GABAergic anaesthetics, such as propofol, boost cortical inhibition by prolonging the tail of the unitary IPSP (inhibitory postsynaptic potential) at GABAA receptors, while increasing the synaptic gain at the slower-acting GABAB receptors. Dissociative anaesthetics act on NMDA receptors to give a voltage-dependent alteration of excitatory synaptic gain. We find that increasing GABAB or NMDA effect can alter the spatiotemporal dynamics of the standard WM, tending to suppress spatial (Turing) patterns in favour of temporal (Hopf) oscillations. The extended WM predicts increased susceptibility to seizure when GABAB effect is increased, particularly if the GABAergic agent reduces gap-junction diffusion. 
We tested these WM predictions with two biological experiments. We found that potentiation of GABAB receptors in slices of mouse cortical tissue tended to enhance seizure-like activity. However, our in vivo investigation of the effect of closure of gap junctions did not reveal any seizure patterns in mouse EEG signals. 
In the second part of this thesis, we present a detailed analysis of the HvP thalamocortical mean-field model for propofol anaesthesia. While we were able to confirm the Hindriks and van Putten predictions of increases in delta and alpha power at low levels of anaesthetic sedation, we find that for deeper anaesthetic effect, the model jumps from the low-firing state to an extremely high-firing stable state (~250 spikes/s), and remains stuck there even at GABAA prolongations as high as 300% which would be expected to induce full comatose suppression of all firing activity. To overcome this pathological behaviour, we tested two possible modifications: first, eliminating the population-dependent anaesthetic sensitivity (efficacy) of the HvP model; second, incorporating reversal potentials and tuning the excitatory sigmoid parameters defining the mapping from voltage to firing rate. The first modification removes the pathological state, but predicts de-creasing alpha and delta power as drug concentration increases. The second modification predicts induction-emergence hysteresis (drug concentration is higher at induction than at emergence), but the alpha rhythm is lost, being replaced by a dominant delta-band oscillation.

year: 2016

title: Romeo and Tusi: An eclectically musical Samoan/Māori Romeo and Juliet from Aotearoa/New Zealand

authors: Houlahan, Mark

subjects: Romeo and Tusi

abstract: Is there a distinctive New Zealand Shakespeare? What ‘new’ approaches to Shakespeare have originated from New Zealand? This article explores the issue by contextualising a version of Romeo and Juliet staged successfully throughout New Zealand in the late 1990s. The production is set against the background of the history of Shakespeare in New Zealand, which goes back to the arrival of Captain Cook on the Endeavour in 1769.

Pacific Underground's Romeo and Tusi sought a looser and more populist kind of Shakespeare performance. They used the conceit of rehearsing the play at high school, where a Māori Romeo and a Samoan Juliet cross community boundaries. Drawing on several music genres, and performing outdoors, they generated a Shakespeare that audiences from a diverse range of ethnic and cultural communities could enjoy.

text: Romeo and Tusi: An eclectically musical Samoan/Māori Romeo and Juliet from Aotearoa/New Zealand Is there a distinctive New Zealand Shakespeare? What ‘new’ approaches to Shakespeare have originated from New Zealand? This article explores the issue by contextualising a version of Romeo and Juliet staged successfully throughout New Zealand in the late 1990s. The production is set against the background of the history of Shakespeare in New Zealand, which goes back to the arrival of Captain Cook on the Endeavour in 1769.

Pacific Underground's Romeo and Tusi sought a looser and more populist kind of Shakespeare performance. They used the conceit of rehearsing the play at high school, where a Māori Romeo and a Samoan Juliet cross community boundaries. Drawing on several music genres, and performing outdoors, they generated a Shakespeare that audiences from a diverse range of ethnic and cultural communities could enjoy.

year: 2009