title: Investigating paradoxical hysteresis effects in the mouse neocortical slice model

authors: Voss, Logan J.

subjects: anesthesia

abstract: Clinically, anesthetic drugs show hysteresis in the plasma drug concentrations at induction versus emergence from anesthesia induced unconsciousness. This is assumed to be the result of pharmacokinetic lag between the plasma and brain effect-site and vice versa. However, recent mathematical and experimental studies demonstrate that anesthetic hysteresis might be due in part to lag in the brain physiology, independent of drug transport delay — so-called “neural inertia”. The aim of this study was to investigate neural inertia in the reduced neocortical mouse slice model. Seizure-like event (SLE) activity was generated by exposing cortical slices to no-magnesium artificial cerebrospinal fluid (aCSF). Concentration–effect loops were generated by manipulating SLE frequency, using the general anesthetic drug etomidate and by altering the aCSF magnesium concentration. The etomidate (24 μM) concentration–effect relationship showed a clear hysteresis, consistent with the slow diffusion of etomidate into slice tissue. Manipulation of tissue excitability, using either carbachol (50 μM) or elevated potassium (5 mM vs 2.5 mM) did not significantly alter the size of etomidate hysteresis loops. Hysteresis in the magnesium concentration–effect relationship was evident, but only when the starting condition was magnesium-containing “normal” aCSF. The in vitro cortical slice manifests pathway-dependent “neural inertia” and may be a valuable model for future investigations into the mechanisms of neural inertia in the cerebral cortex.

text: Investigating paradoxical hysteresis effects in the mouse neocortical slice model Clinically, anesthetic drugs show hysteresis in the plasma drug concentrations at induction versus emergence from anesthesia induced unconsciousness. This is assumed to be the result of pharmacokinetic lag between the plasma and brain effect-site and vice versa. However, recent mathematical and experimental studies demonstrate that anesthetic hysteresis might be due in part to lag in the brain physiology, independent of drug transport delay — so-called “neural inertia”. The aim of this study was to investigate neural inertia in the reduced neocortical mouse slice model. Seizure-like event (SLE) activity was generated by exposing cortical slices to no-magnesium artificial cerebrospinal fluid (aCSF). Concentration–effect loops were generated by manipulating SLE frequency, using the general anesthetic drug etomidate and by altering the aCSF magnesium concentration. The etomidate (24 μM) concentration–effect relationship showed a clear hysteresis, consistent with the slow diffusion of etomidate into slice tissue. Manipulation of tissue excitability, using either carbachol (50 μM) or elevated potassium (5 mM vs 2.5 mM) did not significantly alter the size of etomidate hysteresis loops. Hysteresis in the magnesium concentration–effect relationship was evident, but only when the starting condition was magnesium-containing “normal” aCSF. The in vitro cortical slice manifests pathway-dependent “neural inertia” and may be a valuable model for future investigations into the mechanisms of neural inertia in the cerebral cortex.

year: 2012-01

title: The effect of response requirement and target probability on the performance of dogs during a go/no-go scent detection task

authors: Giezen, Claudia

subjects: scent detection

abstract: As the response threshold required to obtain a reinforcer is increased, the likelihood that the reinforcer will be obtained typically decreases. When a response is reinforced in the presence of a stimulus and not in its absence (i.e., a discriminated operant), the response threshold appears to influence the probability that the response will occur in the presence of the discriminative stimulus. In addition, when the target probability during a task is low, the number of responses performed typically decreases. We examined these two factors, response requirement and target prevalence, in a scent-detection task with domestic dogs where amyl acetate solutions were presented to each dog in an automated apparatus. The dogs were trained to place their nose in a sample port where they had access to samples, and to hold their nose in the port to indicate the sample was positive or to activate a limit switch when the sample was negative (a go/no-go scent detection task). During Experiment One, dogs were presented with various indication thresholds (seconds) which were manipulated systematically to evaluate the influence of response requirement on hit rate and correct rejection rate. During Experiment Two, target prevalence was manipulated systematically. Increasing indication threshold had a significant effect on hit rate when large increase in correct rejection rate as the response requirement was increased in the lower range and high correct rejection rate across most other values tested with a slight drop in hit rate as the response requirement was increased. Experiment Two revealed a small partial eta squared effect on accuracy when target prevalence was increased. Limitations and suggestions for future research are discussed.

text: The effect of response requirement and target probability on the performance of dogs during a go/no-go scent detection task As the response threshold required to obtain a reinforcer is increased, the likelihood that the reinforcer will be obtained typically decreases. When a response is reinforced in the presence of a stimulus and not in its absence (i.e., a discriminated operant), the response threshold appears to influence the probability that the response will occur in the presence of the discriminative stimulus. In addition, when the target probability during a task is low, the number of responses performed typically decreases. We examined these two factors, response requirement and target prevalence, in a scent-detection task with domestic dogs where amyl acetate solutions were presented to each dog in an automated apparatus. The dogs were trained to place their nose in a sample port where they had access to samples, and to hold their nose in the port to indicate the sample was positive or to activate a limit switch when the sample was negative (a go/no-go scent detection task). During Experiment One, dogs were presented with various indication thresholds (seconds) which were manipulated systematically to evaluate the influence of response requirement on hit rate and correct rejection rate. During Experiment Two, target prevalence was manipulated systematically. Increasing indication threshold had a significant effect on hit rate when large increase in correct rejection rate as the response requirement was increased in the lower range and high correct rejection rate across most other values tested with a slight drop in hit rate as the response requirement was increased. Experiment Two revealed a small partial eta squared effect on accuracy when target prevalence was increased. Limitations and suggestions for future research are discussed.

year: 2018

title: Ko wai tō ingoa? The transformative potential of Māori names

authors: Seed-Pihama, Joeliee Elizabeth

subjects: Māori names

abstract: Ingoa tangata (personal names) are an expression of te reo Māori, Māori identity, and tino rangatiratanga (self-determination). Nevertheless, our names are still mispronounced, marginalised and demeaned by individuals and institutions, such as schools, the health system, politics and media. This thesis argues that the gift of a Māori name and the assertion of that name over one’s lifetime is simultaneously a political act of resistance and an act of normalisation – an act of just being Māori. In particular, the thesis reveals how whānau naming practices endure and are important for whānau identity and belonging.

A Kaupapa Māori theoretical approach is used to highlight the mana of our ingoa tangata within te ao Māori (the Māori world). I analyse the experiences of six generations of one whānau and the ways in which they have resisted, reclaimed and regenerated our ingoa tangata and associated practices. Kaupapa Māori theory provides a much-needed theoretical framework that privileges te reo Māori and mātauranga Māori throughout this research. This theory also supports Māori researchers to critique and disrupt Western power dynamics within research as well as maintaining the political imperative of decolonisation and resurgence agendas within the research of Indigenous communities.

This thesis foregrounds Pūrākau as a research method to tell the kōrero ingoa (naming stories) of six generations of one whānau, totalling twenty-six different stories. I explore the possibilities of pūrākau as a method and ako (to teach/ learn) as a powerful component in the building and sharing of stories, as writing tools for the (re)presentation of that material and in expressing the researcher’s positionality. Pūrākau as method also enables the utilisation of our cosmogonies as important sources of mātauranga Māori and therefore as crucial to an analysis of our naming motivations and notions of belonging. Furthermore, I critically analyse the disruptions and interruptions to ingoa tangata caused by institutions of colonialism such as religion, law and education. This research argues for the transformative potential of our ingoa tangata and their associated kōrero ingoa in terms of enhancing identity, embedding whakapapa kōrero and keeping Māori values alive within whānau, and beyond.

text: Ko wai tō ingoa? The transformative potential of Māori names Ingoa tangata (personal names) are an expression of te reo Māori, Māori identity, and tino rangatiratanga (self-determination). Nevertheless, our names are still mispronounced, marginalised and demeaned by individuals and institutions, such as schools, the health system, politics and media. This thesis argues that the gift of a Māori name and the assertion of that name over one’s lifetime is simultaneously a political act of resistance and an act of normalisation – an act of just being Māori. In particular, the thesis reveals how whānau naming practices endure and are important for whānau identity and belonging.

A Kaupapa Māori theoretical approach is used to highlight the mana of our ingoa tangata within te ao Māori (the Māori world). I analyse the experiences of six generations of one whānau and the ways in which they have resisted, reclaimed and regenerated our ingoa tangata and associated practices. Kaupapa Māori theory provides a much-needed theoretical framework that privileges te reo Māori and mātauranga Māori throughout this research. This theory also supports Māori researchers to critique and disrupt Western power dynamics within research as well as maintaining the political imperative of decolonisation and resurgence agendas within the research of Indigenous communities.

This thesis foregrounds Pūrākau as a research method to tell the kōrero ingoa (naming stories) of six generations of one whānau, totalling twenty-six different stories. I explore the possibilities of pūrākau as a method and ako (to teach/ learn) as a powerful component in the building and sharing of stories, as writing tools for the (re)presentation of that material and in expressing the researcher’s positionality. Pūrākau as method also enables the utilisation of our cosmogonies as important sources of mātauranga Māori and therefore as crucial to an analysis of our naming motivations and notions of belonging. Furthermore, I critically analyse the disruptions and interruptions to ingoa tangata caused by institutions of colonialism such as religion, law and education. This research argues for the transformative potential of our ingoa tangata and their associated kōrero ingoa in terms of enhancing identity, embedding whakapapa kōrero and keeping Māori values alive within whānau, and beyond.

year: 2017