title: The time machine. Norman Taylor Memorial Lecture 2002

authors: Lowe, David J.

abstract: I've chosen to talk about five topics dealing with longstanding pedological or paleoenvironmental problems involving tephrostratigraphy. I'll begin with the oldest tephras and work 'stratigraphically upwards' to the youngest. Along the way I'll mention or show a few of the people I've worked with, or who were involved historically in the research areas. I've allowed around five or six minutes for each topic (but I'd be grateful if you didn't set your stopwatches!). As promised, the second part of the talk will begin when we reach the year 1952. Among a range of personal observations relating to the birth of the society and to Norman Taylor, I will attempt to explain how I came to be giving this lecture today.

text: The time machine. Norman Taylor Memorial Lecture 2002 I've chosen to talk about five topics dealing with longstanding pedological or paleoenvironmental problems involving tephrostratigraphy. I'll begin with the oldest tephras and work 'stratigraphically upwards' to the youngest. Along the way I'll mention or show a few of the people I've worked with, or who were involved historically in the research areas. I've allowed around five or six minutes for each topic (but I'd be grateful if you didn't set your stopwatches!). As promised, the second part of the talk will begin when we reach the year 1952. Among a range of personal observations relating to the birth of the society and to Norman Taylor, I will attempt to explain how I came to be giving this lecture today.

year: 2002

title: Investigating the dynamics of a population of spiking neurons across spatial scales

authors: Malluwawadu, Sanduni Chavinka

subjects: Neural populations

abstract: Mean-field models describe bulk neural activity in terms of population-average action potential (spike) rates, but do not attempt to address the variations in the firing activity of individual neurons and the interactions among them. In 2016, Waikato Cortical Modelling group published a purely theoretical model [Steyn-Ross et al, Phys. Rev. E 93.2 (2016): 022402] that provides a more accurate mapping of spiking dynamics, scaling from single neuron to the macroscopic level by regridding the system using a spatial blocking: a bottom-up neural regridding referred to as True-field. A 2D continuum of identical neurons is constructed from a lattice of spiking neurons that are coupled both synaptically (via chemical synapses) and diffusively (via electrical synapses). The spiking behaviour at the single-neuron level is modelled using the Wilson point neuron equations, steered by incoming electrical impulses from adjacent neurons. These equations are then reblocked to form a coarser-spatial resolution by eliminating the high-frequency spatial modes. The existence of diffusive terms in voltage and recovery equations is crucial for this spatial coarse-graining procedure.

The purpose of this thesis is to conduct a preliminary analysis of the True-field model, which has never been tested in simulations before. The coarse-graining procedure employed in this framework results in a set of nonlinear corrections in the model equations. My first challenge is to recover those corrections and conduct numerical investigations to identify the most significant ones. My next challenge is to tune parameters of the True-field model via a comprehensive series of simulations, looking for “realistic” cortical behaviours. Two approaches are used: point simulations of the homogeneous two-neuron cortex, and full 2D grid simulations of a sheet of cortical tissue. Point simulations are straightforward and time efficient but do not provide any information about spatial variations in firing activity; grid simulations allow examination of spatial patterns, but can be challenging to set up, and are computationally expensive in terms of run times and memory requirements. I demonstrate that True-field can reproduce spiking behaviour of a normal brain across multiple levels using a range of blocking ratios: intracellular spiking for low blocking; agglomerated population events (EEG patterns) when blocking is increased. I also show that the model can produce the seizure-like events (SLE) seen in a slice of mouse brain sustained in a bath of artificial cerebro-spinal fluid (aCSF). My grid simulations confirm the generation and propagation of firing activity across the reblocked cortical grid. In conclusion, this new paradigm provides insights about the spiking dynamics of neurons from microscopic to macroscopic levels in a way that neither single-neuron nor mean-field approaches can do.

text: Investigating the dynamics of a population of spiking neurons across spatial scales Mean-field models describe bulk neural activity in terms of population-average action potential (spike) rates, but do not attempt to address the variations in the firing activity of individual neurons and the interactions among them. In 2016, Waikato Cortical Modelling group published a purely theoretical model [Steyn-Ross et al, Phys. Rev. E 93.2 (2016): 022402] that provides a more accurate mapping of spiking dynamics, scaling from single neuron to the macroscopic level by regridding the system using a spatial blocking: a bottom-up neural regridding referred to as True-field. A 2D continuum of identical neurons is constructed from a lattice of spiking neurons that are coupled both synaptically (via chemical synapses) and diffusively (via electrical synapses). The spiking behaviour at the single-neuron level is modelled using the Wilson point neuron equations, steered by incoming electrical impulses from adjacent neurons. These equations are then reblocked to form a coarser-spatial resolution by eliminating the high-frequency spatial modes. The existence of diffusive terms in voltage and recovery equations is crucial for this spatial coarse-graining procedure.

The purpose of this thesis is to conduct a preliminary analysis of the True-field model, which has never been tested in simulations before. The coarse-graining procedure employed in this framework results in a set of nonlinear corrections in the model equations. My first challenge is to recover those corrections and conduct numerical investigations to identify the most significant ones. My next challenge is to tune parameters of the True-field model via a comprehensive series of simulations, looking for “realistic” cortical behaviours. Two approaches are used: point simulations of the homogeneous two-neuron cortex, and full 2D grid simulations of a sheet of cortical tissue. Point simulations are straightforward and time efficient but do not provide any information about spatial variations in firing activity; grid simulations allow examination of spatial patterns, but can be challenging to set up, and are computationally expensive in terms of run times and memory requirements. I demonstrate that True-field can reproduce spiking behaviour of a normal brain across multiple levels using a range of blocking ratios: intracellular spiking for low blocking; agglomerated population events (EEG patterns) when blocking is increased. I also show that the model can produce the seizure-like events (SLE) seen in a slice of mouse brain sustained in a bath of artificial cerebro-spinal fluid (aCSF). My grid simulations confirm the generation and propagation of firing activity across the reblocked cortical grid. In conclusion, this new paradigm provides insights about the spiking dynamics of neurons from microscopic to macroscopic levels in a way that neither single-neuron nor mean-field approaches can do.

year: 2021

title: Mental health and wellbeing for young people from intersectional identity groups: Inequity for Māori, Pacific, Rainbow young people, and those with a disabling condition

authors: Roy, Rituparna

subjects: Māori

abstract: ‘Intersectionality’ describes the converging effects of ethnicity, gender, sexuality, disability, and other social group characteristics that influence life experiences. We draw on a representative study of year 9-13 students in Tai Tokerau, Tāmaki Makaurau, and Waikato (Youth19) to explore differences in mental health and wellbeing outcomes for young people from a selection of intersectional identities (Māori, Pasifika, Rainbow, and young people with a Disabling Condition). We found a pervasive pattern of inequity for young people who have intersectional identities compared to those from the majority groups (i.e. Pākehā, non-disabled, cis-heterosexual youth). Intersectional youth had higher levels of inequity and faced a greater array of inequities. There was evidence of an additive effect for some indicators. Thematic analysis of open-text survey responses found the need for positive inclusive environments, and support for all young people, including those at the intersections of identity. Drawing on the findings, we offered several systemslevel policy recommendations, including strategies to improve inclusiveness and reduce discrimination.

text: Mental health and wellbeing for young people from intersectional identity groups: Inequity for Māori, Pacific, Rainbow young people, and those with a disabling condition ‘Intersectionality’ describes the converging effects of ethnicity, gender, sexuality, disability, and other social group characteristics that influence life experiences. We draw on a representative study of year 9-13 students in Tai Tokerau, Tāmaki Makaurau, and Waikato (Youth19) to explore differences in mental health and wellbeing outcomes for young people from a selection of intersectional identities (Māori, Pasifika, Rainbow, and young people with a Disabling Condition). We found a pervasive pattern of inequity for young people who have intersectional identities compared to those from the majority groups (i.e. Pākehā, non-disabled, cis-heterosexual youth). Intersectional youth had higher levels of inequity and faced a greater array of inequities. There was evidence of an additive effect for some indicators. Thematic analysis of open-text survey responses found the need for positive inclusive environments, and support for all young people, including those at the intersections of identity. Drawing on the findings, we offered several systemslevel policy recommendations, including strategies to improve inclusiveness and reduce discrimination.

year: 2023