title: Subthreshold dynamics of a single neuron from a Hamiltonian perspective

authors: Wilson, Marcus T.

subjects: brain models

abstract: We use Hamilton's equations of classical mechanics to investigate the behavior of a cortical neuron on the approach to an action potential. We use a two-component dynamic model of a single neuron, due to Wilson, with added noise inputs. We derive a Lagrangian for the system, from which we construct Hamilton's equations. The conjugate momenta are found to be linear combinations of the noise input to the system. We use this approach to consider theoretically and computationally the most likely manner in which such a modeled neuron approaches a firing event. We find that the firing of a neuron is a result of a drop in inhibition, due to a temporary increase in negative bias of the mean noise input to the inhibitory control equation. Moreover, we demonstrate through theory and simulation that, on average, the bias in the noise increases in an exponential manner on the approach to an action potential. In the Hamiltonian description, an action potential can therefore be considered a result of the exponential growth of the conjugate momenta variables pulling the system away from its equilibrium state, into a nonlinear regime.

text: Subthreshold dynamics of a single neuron from a Hamiltonian perspective We use Hamilton's equations of classical mechanics to investigate the behavior of a cortical neuron on the approach to an action potential. We use a two-component dynamic model of a single neuron, due to Wilson, with added noise inputs. We derive a Lagrangian for the system, from which we construct Hamilton's equations. The conjugate momenta are found to be linear combinations of the noise input to the system. We use this approach to consider theoretically and computationally the most likely manner in which such a modeled neuron approaches a firing event. We find that the firing of a neuron is a result of a drop in inhibition, due to a temporary increase in negative bias of the mean noise input to the inhibitory control equation. Moreover, we demonstrate through theory and simulation that, on average, the bias in the noise increases in an exponential manner on the approach to an action potential. In the Hamiltonian description, an action potential can therefore be considered a result of the exponential growth of the conjugate momenta variables pulling the system away from its equilibrium state, into a nonlinear regime.

year: 2008

title: “Not another patient through the revolving door”: A case study analysis of six women’s experiences with pregnancy terminations in New Zealand.

authors: Lee, Katherine Louise

subjects: Pregnancy termination

abstract: This thesis investigates an under-researched and largely ignored area in New Zealand, specifically six young women’s experiences of pregnancy termination in a New Zealand context. The aim of this research is twofold: to investigate the interconnection between intimate relationships and pregnancy terminations, and to describe and analyse the experiences of quality of care provided in New Zealand pregnancy termination settings. 

This research is conducted using a narrative methodology that allows each participant to have their own unique ‘voice’ and to offer valuable and rich insights into their personal experiences of pregnancy termination. Six participants were selected who met the criteria of being under 25 years of age at the time of their terminations. These participants were interviewed individually on three separate occasions using a qualitative semi-structured interview schedule with themes that included life before falling pregnant, culture and religion, intimate relationship pre- and post-termination, intimate relationship education (if any) provided at school, interaction with health professionals, accessibility, experiences on the day of the procedure, and participants’ advice for young women contemplating a termination. 

The findings from this thesis demonstrate a plethora of consequences for intimate relationships and the delivery of quality of care throughout the termination process. In terms of intimate relationships, the dissolution of the ‘honeymoon period’ exacerbated issues for women undergoing terminations. The quality of the relationship was found to be an important contributor to decision-making, particularly when the intimate partner was invited to share this responsibility. Problems arose in those relationships where there were incongruent experiences concerning the termination — for example, when one individual in the relationship was coping but the other was not. Irrespective of the quality of the relationship one key finding is that terminations appear to have a significant negative impact on future relationships. Interestingly, some participants chose to conceal their terminations from future intimate partners when then knew their partners were opposed to pregnancy terminations on ethical grounds. 

This thesis also highlights the considerable barriers to accessing termination clinics because they are located in the main centres and required most participants to travel to these clinics. Many participants struggled to ‘get a foot in the door’ and this often resulted in delayed entry to the service. Participants were aware of the role of the health professionals as the legal gatekeepers to the termination process and this led some to conceal their emotions, further heightening their stress on the day of the termination. The participants’ experiences of simply being a ‘number’ and part of the ‘revolving door’ process contributed towards their negative perceptions about, and experiences of, quality of care. The combination of their desire for but absence of tangibility, coupled with the non-alignment of participants’ expectations with the quality of care service they received, led some participants to have negative experiences of the termination process. 

The narratives that have been offered by the six young women who have had a termination provide valuable insights into, and reflections about, their personal experiences with a legal process that for many New Zealanders still remains ‘behind closed doors’.

text: “Not another patient through the revolving door”: A case study analysis of six women’s experiences with pregnancy terminations in New Zealand. This thesis investigates an under-researched and largely ignored area in New Zealand, specifically six young women’s experiences of pregnancy termination in a New Zealand context. The aim of this research is twofold: to investigate the interconnection between intimate relationships and pregnancy terminations, and to describe and analyse the experiences of quality of care provided in New Zealand pregnancy termination settings. 

This research is conducted using a narrative methodology that allows each participant to have their own unique ‘voice’ and to offer valuable and rich insights into their personal experiences of pregnancy termination. Six participants were selected who met the criteria of being under 25 years of age at the time of their terminations. These participants were interviewed individually on three separate occasions using a qualitative semi-structured interview schedule with themes that included life before falling pregnant, culture and religion, intimate relationship pre- and post-termination, intimate relationship education (if any) provided at school, interaction with health professionals, accessibility, experiences on the day of the procedure, and participants’ advice for young women contemplating a termination. 

The findings from this thesis demonstrate a plethora of consequences for intimate relationships and the delivery of quality of care throughout the termination process. In terms of intimate relationships, the dissolution of the ‘honeymoon period’ exacerbated issues for women undergoing terminations. The quality of the relationship was found to be an important contributor to decision-making, particularly when the intimate partner was invited to share this responsibility. Problems arose in those relationships where there were incongruent experiences concerning the termination — for example, when one individual in the relationship was coping but the other was not. Irrespective of the quality of the relationship one key finding is that terminations appear to have a significant negative impact on future relationships. Interestingly, some participants chose to conceal their terminations from future intimate partners when then knew their partners were opposed to pregnancy terminations on ethical grounds. 

This thesis also highlights the considerable barriers to accessing termination clinics because they are located in the main centres and required most participants to travel to these clinics. Many participants struggled to ‘get a foot in the door’ and this often resulted in delayed entry to the service. Participants were aware of the role of the health professionals as the legal gatekeepers to the termination process and this led some to conceal their emotions, further heightening their stress on the day of the termination. The participants’ experiences of simply being a ‘number’ and part of the ‘revolving door’ process contributed towards their negative perceptions about, and experiences of, quality of care. The combination of their desire for but absence of tangibility, coupled with the non-alignment of participants’ expectations with the quality of care service they received, led some participants to have negative experiences of the termination process. 

The narratives that have been offered by the six young women who have had a termination provide valuable insights into, and reflections about, their personal experiences with a legal process that for many New Zealanders still remains ‘behind closed doors’.

year: 2016

title: Different coloured tears: Dual cultural identity and Tangihanga – A directed study

authors: Edge, Kiri

subjects: bereavement

abstract: Although whānau/family that are configured by both Pākehā and Māori identities number significantly within New Zealand, there has been little or no attention paid to the ways in which these identities influence the bereavement processes that will inevitably impact upon the lives of these whānau/family. The present study explored the experiences of an individual, whose whānau/family included two life ways; Māori and Pākehā. Of specific focus was the ways in which these identities influenced his bereavement subsequent to the death of his beloved wife, who was of Māori descent. One elderly male Pākehā participant was interviewed, using an open-ended narrative approach. The interview was semi structured around five broad themes, but the focus was upon the participant’s experiences and his preference in expressing these. The data analysis utilised a thematic process, which allowed the participant’s experiences to determine the emergent themes. The results depicted the diversity of issues that may be raised for dual cultural whānau/family within bereavement processes. Two central themes are discussed in relation to intercultural conflict and the eventual resolution that was created. Decision making processes, cultural and language differences played significant roles within the conflict and exclusion experienced by the participant. Communication and compromise provided resolution to the prior conflicts experienced. This created positive and unexpected outcomes which resulted in increased understandings and the strengthening of links between the participant, his whānau/family and his wife’s marae.

text: Different coloured tears: Dual cultural identity and Tangihanga – A directed study Although whānau/family that are configured by both Pākehā and Māori identities number significantly within New Zealand, there has been little or no attention paid to the ways in which these identities influence the bereavement processes that will inevitably impact upon the lives of these whānau/family. The present study explored the experiences of an individual, whose whānau/family included two life ways; Māori and Pākehā. Of specific focus was the ways in which these identities influenced his bereavement subsequent to the death of his beloved wife, who was of Māori descent. One elderly male Pākehā participant was interviewed, using an open-ended narrative approach. The interview was semi structured around five broad themes, but the focus was upon the participant’s experiences and his preference in expressing these. The data analysis utilised a thematic process, which allowed the participant’s experiences to determine the emergent themes. The results depicted the diversity of issues that may be raised for dual cultural whānau/family within bereavement processes. Two central themes are discussed in relation to intercultural conflict and the eventual resolution that was created. Decision making processes, cultural and language differences played significant roles within the conflict and exclusion experienced by the participant. Communication and compromise provided resolution to the prior conflicts experienced. This created positive and unexpected outcomes which resulted in increased understandings and the strengthening of links between the participant, his whānau/family and his wife’s marae.

year: 2010-01