title: A Population Model of the Thalamus and its Wave Interactions with the Cortex

authors: Müller, Eli Justin

subjects: Thalamus

abstract: In this thesis we construct a population model of the thalamus based on the mean-field cortex developed by Steyn-Ross et al. and Liley et al. We allow interactions between the thalamus and cortex via damped wave equations and show spindle-like oscillations (10-15 Hz)  propagating from the thalamic reticular population into the cortical populations.
We first consider a mean-field model of a cortex that is isolated from time-dependent sub-cortical inputs. The model is a continuum theory based on the electrical activity of a neural mass called the macrocolumn, containing groups of excitatory and inhibitory neurons. We demonstrate induction of 'unconsciousness' in the macrocoulmn under propofol-like general anaesthetic, and show there is a hysteretic separation between points of 'loss of consciousness' and 'recovery of consciousness'.
The thalamus, a sub-cortical structure important to the relay of sensory input into the cortex, is described using a revised set of equations based on the mean-field cortical model. We define two neuron types within the thalamus: the specific group, assumed to be excitatory, and the reticular group, assumed to be inhibitory. A new bimodal mapping function is developed to relate mean membrane potentials to mean firing rates within the thalamic macrocolumn. This bimodal function is generated by combining two sigmoidal functions, and is a representation of the observed increase in the firing rates of reticular neurons at hyperpolarized membrane potentials. In contrast, the mapping function for specific population is modelled by a standard sigmoid. We investigate the isolated dynamics of the mean-field thalamus, using parameters from Robinson et al., and find spindle-like oscillations emerge following a transition from unstable equilibrium states to stable states consistent with the linear stability analysis.
A coupling of the isolated cortical and thalamic systems is accomplished using four damped wave equations. We investigate the stationary states of the thalamo-cortical model and find the spindle-like oscillations present in the thalamus propagate into the cortical populations.

text: A Population Model of the Thalamus and its Wave Interactions with the Cortex In this thesis we construct a population model of the thalamus based on the mean-field cortex developed by Steyn-Ross et al. and Liley et al. We allow interactions between the thalamus and cortex via damped wave equations and show spindle-like oscillations (10-15 Hz)  propagating from the thalamic reticular population into the cortical populations.
We first consider a mean-field model of a cortex that is isolated from time-dependent sub-cortical inputs. The model is a continuum theory based on the electrical activity of a neural mass called the macrocolumn, containing groups of excitatory and inhibitory neurons. We demonstrate induction of 'unconsciousness' in the macrocoulmn under propofol-like general anaesthetic, and show there is a hysteretic separation between points of 'loss of consciousness' and 'recovery of consciousness'.
The thalamus, a sub-cortical structure important to the relay of sensory input into the cortex, is described using a revised set of equations based on the mean-field cortical model. We define two neuron types within the thalamus: the specific group, assumed to be excitatory, and the reticular group, assumed to be inhibitory. A new bimodal mapping function is developed to relate mean membrane potentials to mean firing rates within the thalamic macrocolumn. This bimodal function is generated by combining two sigmoidal functions, and is a representation of the observed increase in the firing rates of reticular neurons at hyperpolarized membrane potentials. In contrast, the mapping function for specific population is modelled by a standard sigmoid. We investigate the isolated dynamics of the mean-field thalamus, using parameters from Robinson et al., and find spindle-like oscillations emerge following a transition from unstable equilibrium states to stable states consistent with the linear stability analysis.
A coupling of the isolated cortical and thalamic systems is accomplished using four damped wave equations. We investigate the stationary states of the thalamo-cortical model and find the spindle-like oscillations present in the thalamus propagate into the cortical populations.

year: 2014

title: Exploring the effects of vicarious trauma in New Zealand practitioners

authors: Rakei, Nina Roera Maheaiterangi

subjects: Vicarious trauma

abstract: Vicarious trauma is an occupational stress reaction that affects health professionals on different levels. This is caused from empathic engagements with clients and being exposed to traumatic material on a regular basis. In this study it was clear that practitioner’s experience negative as well as positive shifts in their world views and sense of self. Eleven health practitioners were interviewed to explore what led them into their desired helping profession and how they have managed to practice effectively. Related concepts of psychological impacts are discussed describing the relationship between posttraumatic stress type features and vicarious trauma that are experienced by health professionals. Information collected from interviews explored the themes between the shared stories and the literature on vicarious trauma effects. Four sections explore: motives for helping, personal experiences of vicarious trauma, identifying it in others and various ways of coping with effects. Various sub-themes are explored from each major theme using the constructivist self-development theory. In conclusion with the findings from the data collected and previous research, this study shares lived experiences of the effects of vicarious trauma.

text: Exploring the effects of vicarious trauma in New Zealand practitioners Vicarious trauma is an occupational stress reaction that affects health professionals on different levels. This is caused from empathic engagements with clients and being exposed to traumatic material on a regular basis. In this study it was clear that practitioner’s experience negative as well as positive shifts in their world views and sense of self. Eleven health practitioners were interviewed to explore what led them into their desired helping profession and how they have managed to practice effectively. Related concepts of psychological impacts are discussed describing the relationship between posttraumatic stress type features and vicarious trauma that are experienced by health professionals. Information collected from interviews explored the themes between the shared stories and the literature on vicarious trauma effects. Four sections explore: motives for helping, personal experiences of vicarious trauma, identifying it in others and various ways of coping with effects. Various sub-themes are explored from each major theme using the constructivist self-development theory. In conclusion with the findings from the data collected and previous research, this study shares lived experiences of the effects of vicarious trauma.

year: 2016

title: Developing a kaupapa Māori evaluation model – one size fits all?

authors: Masters-Awatere, Bridgette

subjects: Maori health

abstract: Health statistics in Aotearoa (New Zealand) highlight that Māori, the indigenous people Aotearoa have poorer health than non- Māori. In response to the statistics a number of Māori health providers have established services that address specific areas of need in their regions. Initially there were minimal accountability requirements of providers. However, changes in the health system now mean that groups wanting to establish a new service must provide accountability measures before, during and after the funding has been allocated. As a result providers need to develop a rationale behind their decisions and assess the measure of change that has taken place as a result of the service or programme to ensure continued funding. The requirements reflect the dominant Western paradigm in which health promotion is understood to be about producing specific quantifiable behaviour changes in individuals. Māori health providers on the other hand have tended to take a holistic approach to health. Thus they have found themselves in the position of trying to show change within a paradigm where measurements are not easily taken. This has created frustration amongst Māori providers who face losing their funding because of an inability to report measurable outcomes using a framework that does not apply to their culture.

text: Developing a kaupapa Māori evaluation model – one size fits all? Health statistics in Aotearoa (New Zealand) highlight that Māori, the indigenous people Aotearoa have poorer health than non- Māori. In response to the statistics a number of Māori health providers have established services that address specific areas of need in their regions. Initially there were minimal accountability requirements of providers. However, changes in the health system now mean that groups wanting to establish a new service must provide accountability measures before, during and after the funding has been allocated. As a result providers need to develop a rationale behind their decisions and assess the measure of change that has taken place as a result of the service or programme to ensure continued funding. The requirements reflect the dominant Western paradigm in which health promotion is understood to be about producing specific quantifiable behaviour changes in individuals. Māori health providers on the other hand have tended to take a holistic approach to health. Thus they have found themselves in the position of trying to show change within a paradigm where measurements are not easily taken. This has created frustration amongst Māori providers who face losing their funding because of an inability to report measurable outcomes using a framework that does not apply to their culture.

year: 2002