title: Using neural fields to model motor evoked potentials due to transcranial magnetic stimulation

authors: Wilson, Marcus T.

abstract: Neural field models, in which populations of neurons are described through ensemble-averaged properties such as firing rate and axonal flux, have been well-used to describe electroencephalogram (EEG) effects in natural sleep, anaesthesia and epilepsy. Changes in EEG due to stimulation by electromagnetic fields have also been studied. However, experimental data concerning transcranial magnetic stimulation (TMS) is dominated by measurements of motor-evoked potentials (MEPs). To use neural fields for TMS, a model of the MEP is required. In this work, an existing model has been augmented by addition of populations of cells describing stages of the MEP pathway previously neglected by neural field models. The model includes coupled populations of excitatory and inhibitory layer 2/3 cortical neurons, stimulated by an external field. These populations feed an additional population of layer 5 neurons, which also couples weakly to the external field. The layer 5 neurons feed motoneurons, from which a measure of the motor-evoked potential is constructed. After some tuning of parameters, the extra populations have resulted in a better model of the MEP than previously present in neural field models. The model reproduces the non-linear response to an increase in stimulation amplitude. With a paired-pulse protocol it reproduces the experimental effects of intracortical facilitation and long-interval intracortical inhibition, though it shows only weak short-interval intracortical inhibition. The experimental direct and indirect waves of activation from the layer 5 neurons are not adequately reproduced. Small changes in synaptic weight can give much greater changes in MEP response. In conclusion, the model is promising but it raises questions about whether neural field models are really appropriate for the study of many TMS effects.

text: Using neural fields to model motor evoked potentials due to transcranial magnetic stimulation Neural field models, in which populations of neurons are described through ensemble-averaged properties such as firing rate and axonal flux, have been well-used to describe electroencephalogram (EEG) effects in natural sleep, anaesthesia and epilepsy. Changes in EEG due to stimulation by electromagnetic fields have also been studied. However, experimental data concerning transcranial magnetic stimulation (TMS) is dominated by measurements of motor-evoked potentials (MEPs). To use neural fields for TMS, a model of the MEP is required. In this work, an existing model has been augmented by addition of populations of cells describing stages of the MEP pathway previously neglected by neural field models. The model includes coupled populations of excitatory and inhibitory layer 2/3 cortical neurons, stimulated by an external field. These populations feed an additional population of layer 5 neurons, which also couples weakly to the external field. The layer 5 neurons feed motoneurons, from which a measure of the motor-evoked potential is constructed. After some tuning of parameters, the extra populations have resulted in a better model of the MEP than previously present in neural field models. The model reproduces the non-linear response to an increase in stimulation amplitude. With a paired-pulse protocol it reproduces the experimental effects of intracortical facilitation and long-interval intracortical inhibition, though it shows only weak short-interval intracortical inhibition. The experimental direct and indirect waves of activation from the layer 5 neurons are not adequately reproduced. Small changes in synaptic weight can give much greater changes in MEP response. In conclusion, the model is promising but it raises questions about whether neural field models are really appropriate for the study of many TMS effects.

year: 2018

title: Evaluating return-to-work programmes after critical incidents: a review of the evidence

authors: Sutton, Anna

abstract: In most countries, employers have a responsibility to ensure the safety and well-being of their employees, including those who work in hazardous occupations. Policing can be a hazardous occupation and officers can face physical threats to life. Yet in the police service, there appears to be a dichotomy between treating officers involved in critical incidents solely in terms of serious clinical issues (e.g. PTSD) whilst simultaneously setting a strong expectation that these officers will return to work quickly and with little effect on their work performance. We review the research literature on return-to-work programmes to establish how much the effect of critical incidents on officers’ work performance is being considered and to identify future research directions. Findings indicate an emphasis on improving mental health but a lack of research into occupational outcomes. They also reveal distinct promise for peer-led reintegration programmes.

text: Evaluating return-to-work programmes after critical incidents: a review of the evidence In most countries, employers have a responsibility to ensure the safety and well-being of their employees, including those who work in hazardous occupations. Policing can be a hazardous occupation and officers can face physical threats to life. Yet in the police service, there appears to be a dichotomy between treating officers involved in critical incidents solely in terms of serious clinical issues (e.g. PTSD) whilst simultaneously setting a strong expectation that these officers will return to work quickly and with little effect on their work performance. We review the research literature on return-to-work programmes to establish how much the effect of critical incidents on officers’ work performance is being considered and to identify future research directions. Findings indicate an emphasis on improving mental health but a lack of research into occupational outcomes. They also reveal distinct promise for peer-led reintegration programmes.

year: 2022-07-22

title: Food insecurity in urban New Zealand. The case of the Kopa family

authors: Graham, Rebekah Sarah

abstract: Poverty brings insecurity and chaos into the home, forcing families to develop strategies for navigating the difficulties of food insecurity. We document how one household, the Kopa family, responds to poverty in ad hoc and agentive ways that assist and hinder their attempts to keep themselves fed. This study is based on a series of eight qualitative interviews with family members, including photo-elicitation and go-along techniques, as well as extensive field notes from more casual research interactions such as shared meals. Our analysis demonstrates how food insecurity shapes this family’s culturally patterned social practices surrounding the procurement, consumption, and sharing of food.

text: Food insecurity in urban New Zealand. The case of the Kopa family Poverty brings insecurity and chaos into the home, forcing families to develop strategies for navigating the difficulties of food insecurity. We document how one household, the Kopa family, responds to poverty in ad hoc and agentive ways that assist and hinder their attempts to keep themselves fed. This study is based on a series of eight qualitative interviews with family members, including photo-elicitation and go-along techniques, as well as extensive field notes from more casual research interactions such as shared meals. Our analysis demonstrates how food insecurity shapes this family’s culturally patterned social practices surrounding the procurement, consumption, and sharing of food.

year: 2018