Elizabeth Bowman - Academia.edu (original) (raw)

Papers by Elizabeth Bowman

SSRN Electronic Journal, 2020

The non-medical use of pharmaceuticals such as methylphenidate and modafinil for cognitive enhanc... more The non-medical use of pharmaceuticals such as methylphenidate and modafinil for cognitive enhancement has been explored in college students, medical students and various professions in the US and Europe. We present results of an anonymous online survey of such use among members of the Australian financial services industry. Our hypothesis was that industry sectors would report different preferences for different drugs, reflecting different workplace task demands. The survey was advertised to industry groups, online media articles, and social media outlets between September 2016 and October 2017. Industry sector, hours worked per week, and other demographic and personal health factors were also surveyed. 372 responses were received, of which 140 were valid and complete, and 69 were variously incomplete but usable. Different sectors of the financial services industry reported significantly different rates of use among colleagues. Respondents from different industry sectors also nominated different substances as most prevalent with significantly different frequencies. There was a significant difference in reported hours slept per night between those who reported workplace use and those who did not. A number of side effects were also reported, including headaches and mood swings. This is an important first step in exploring the use of attempts at pharmaceutical cognitive enhancement in competitive professional workplaces with diverse task demands.

SSRN Electronic Journal, 2019

We study how markets help spread knowledge about solutions to the standard but computationally ha... more We study how markets help spread knowledge about solutions to the standard but computationally hard problem of maximizing value over indivisible goods subject to a budget constraint. In a first experiment, we f ind that complete markets are fairly ineffective. Still, participants use prices and volumes to improve their choices. In a second experiment, inspired by the notion of oracles in computer science, we show that a reduction to only one carefully chosen asset dramatically improves price quality and knowledge dispersion. Our analysis provides a formalization of Hayek's (1945) conjecture that markets help disseminate knowledge in society.

JIMD reports, Jan 15, 2017

Niemann-Pick disease type C (NPC) is a rare neurometabolic disorder resulting in impaired intrace... more Niemann-Pick disease type C (NPC) is a rare neurometabolic disorder resulting in impaired intracellular lipid trafficking. The only disease-modifying treatment currently available is miglustat, an iminosugar that inhibits the accumulation of lipid metabolites in neurons and other cells. This longitudinal diffusion tensor imaging (DTI) study examined how the rate of white matter change differed between treated and non-treated adult-onset NPC patient groups. Nine adult-onset NPC patients (seven undergoing treatment with miglustat, two not treated) underwent DTI neuroimaging. Rates of change in white matter structure as indexed by Tract-Based Spatial Statistics (TBSS) of fractional anisotropy were compared between treated and untreated patients. Treated patients were found to have a significantly slower rate of white matter change in the corticospinal tracts, the thalamic radiation and the inferior longitudinal fasciculus. This is further evidence that miglustat treatment may have a pr...

Orphanet journal of rare diseases, Jan 21, 2015

Niemann-Pick Type C disease (NPC), is an autosomal recessive neurovisceral disorder of lipid meta... more Niemann-Pick Type C disease (NPC), is an autosomal recessive neurovisceral disorder of lipid metabolism. One characteristic feature of NPC is a vertical supranuclear gaze palsy particularly affecting saccades. However, horizontal saccades are also impaired and as a consequence a parameter related to horizontal peak saccadic velocity was used as an outcome measure in the clinical trial of miglustat, the first drug approved in several jurisdictions for the treatment of NPC. As NPC-related neuropathology is widespread in the brain we examined a wider range of horizontal saccade parameters and to determine whether these showed treatment-related improvement and, if so, if this was maintained over time. Nine adult NPC patients participated in the study; 8 were treated with miglustat for periods between 33 and 61 months. Data were available for 2 patients before their treatment commenced and 1 patient was untreated. Tasks included reflexive saccades, antisaccades and self-paced saccades, w...

SSRN Electronic Journal, 2017

We study a situation where all market participants are endowed with the same information ex ante ... more We study a situation where all market participants are endowed with the same information ex ante but valuation of securities is computationally intractable. More specifically, security values are given by the solution of a 0-1 knapsack problem, an NP-hard computational problem. We demonstrate experimentally that the quality of security prices decreases substantially as the computational complexity-that is, the amount of computational resources required to solve the knapsack problem-increases. We also show that market participants who were more successful at solving the knapsack problem, either due to skill or chance, made more profit. At the same time, market prices did not reflect security values, even though some participants knew them. These results suggest that the Efficient Market Hypothesis does not hold when computational complexity of security valuation is high. They also suggest that, given the high computational complexity of many economic problems, the Efficient Market Hypothesis is only plausible under very specific, and possibly rare, circumstances.

Journal of Neurology, 2015

Niemann-Pick disease type C (NPC) is a rare neurovisceral disorder resulting in impaired intracel... more Niemann-Pick disease type C (NPC) is a rare neurovisceral disorder resulting in impaired intracellular lipid trafficking. The only disease-modifying treatment available to date is miglustat, an iminosugar inhibiting the accumulation of lipid by-products in neurons. This study explored how changes in cerebellar grey and white matter volumes, and in subcortical volumes, related to patient treatment status and disability and ataxia ratings. Nine adult-onset NPC patients and 17 matched controls underwent T1-weighted MRI. One patient was not receiving miglustat, and pre-treatment data were available for a further patient. Semi-automated cerebellar and subcortical segmentation was undertaken, and the rates of change in putamen, hippocampal, thalamic and caudal volumes, and grey and white matter cerebellar volumes, were compared to rates of change in Iturriaga disability score, Brief Ataxia Rating Scale (BARS), and horizontal saccadic gain. Untreated NPC patients appeared to lose cerebellar grey and white matter, bilateral thalamic volume, and right caudate volume faster than treated patients. Cerebellar grey matter volume loss and volume loss in the left thalamus were significantly correlated with Iturriaga disability scale changes. Change in both cerebellar grey and white matter was correlated with decrease in horizontal saccadic gain, but not with change in BARS. This is the first study to examine longitudinal treatment effects of miglustat on cerebellar and subcortical volumes in patients with adult-onset NPC, and is evidence that miglustat may have a protective effect on cerebellar and subcortical structure and function.

PLoS ONE, 2012

Niemann-Pick Type C disease (NPC) is a rare genetic disorder of lipid metabolism. A parameter rel... more Niemann-Pick Type C disease (NPC) is a rare genetic disorder of lipid metabolism. A parameter related to horizontal saccadic peak velocity was one of the primary outcome measures in the clinical trial assessing miglustat as a treatment for NPC. Neuropathology is widespread in NPC, however, and could be expected to affect other saccadic parameters. We compared horizontal saccadic velocity, latency, gain, antisaccade error percentage and self-paced saccade generation in 9 adult NPC patients to data from 10 age-matched controls. These saccadic measures were correlated with appropriate MRI-derived brain structural measures (e.g., dorsolateral prefrontal cortex, frontal eye fields, supplemental eye fields, parietal eye fields, pons, midbrain and cerebellar vermis) and with measures of disease severity and duration. The best discriminators between groups were reflexive saccade gain and the two volitional saccade measures. Gain was also the strongest correlate with disease severity and duration. Most of the saccadic measures showed strongly significant correlations with neurophysiologically appropriate brain regions. While our patient sample is small, the apparent specificity of these relationships suggests that as new diagnostic methods and treatments become available for NPC, a broader range of saccadic measures may be useful tools for the assessment of disease progression and treatment efficacy.

Visual Neuroscience, 2006

Visual evoked responses to dichoptically presented multifocal stimuli were recorded for 92 eyes. ... more Visual evoked responses to dichoptically presented multifocal stimuli were recorded for 92 eyes. Two stimulus variants were explored: temporally sparse and rapidly contrast reversing. We used hierarchical decomposition (HD) to represent the multifocal responses in terms of a small number of potentially unique component waveforms that are interrelated in a multivariate linear autoregressive (MLAR) relationship. The HD method exploits temporal correlations over a range of delays in the responses to estimate parallel, feedforward and feedback relationships between the HD components. Three HD components having temporal interrelationships constrained (at P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) to a moving approximately 20 ms window could describe the multifocal responses well (median r2-values up to 90%). HD components were similar for both stimulus types and the component waveforms were temporally correlated, especially the first and third components. The data set was large enough to estimate separate HD components for each multifocal stimulus region. The component waveforms differed somewhat by region but the MLAR relationships were similar. At short delays parallel processing dominated. At longer delays the proportion of response drives that were attributed to feedback and feedforward relationships grew. Overall HD analysis seems to provide an informed summary of multifocal responses and insights into their sources.

Visual Neuroscience, 2005

Temporally sparse stimuli have been found to produce larger multifocal visual evoked potentials t... more Temporally sparse stimuli have been found to produce larger multifocal visual evoked potentials than rapid contrast-reversal stimuli. We compared the contrast-response functions of conventional contrast-reversing~CR! stimuli and three grades of temporally sparse stimuli, examining both the changes in response amplitude and signal-to-noise ratio~SNR!. All stimuli were presented dichoptically to normal adult human subjects. One stimulus variant, the slowest pattern pulse, had interleaved monocular and binocular stimuli. Response amplitudes and SNRs were similar for all stimuli at contrast 0.4 but grew faster with increasing contrast for the sparser stimuli. The best sparse stimulus provided an SNR improvement that corresponded to a recording time improvement of 2.6 times relative to that required for contrast reversing stimuli. Multiple regression of log-transformed response metrics characterized the contrast-response functions by fitting power-law relationships. The exponents for the two sparsest stimuli were significantly larger~P Ͻ 0.001! than for the CR stimuli, as were the mean response amplitudes and signal-to-noise ratios for these stimuli. The contrast-dependent response enhancement is discussed with respect to the possible influences of rapid retinal contrast gain control, or intracortical and cortico-geniculate feedback.

Neurology, 2009

The autosomal recessive disorder Niemannn-Pick type C (NPC) presents in adulthood with psychosis ... more The autosomal recessive disorder Niemannn-Pick type C (NPC) presents in adulthood with psychosis or cognitive deficits associated with supranuclear gaze palsies. While saccadic innervation to the extraocular muscles is generated in the brainstem, the frontal lobes play an integral role in the initiation of volitional saccades and the suppression of unwanted reflexive saccades. No study has examined the frontally driven volitional control of saccadic eye movements in NPC.

Molecular Genetics and Metabolism, 2013

Background and purpose: Cerebellar Purkinje cells are known to be highly vulnerable to neuronal p... more Background and purpose: Cerebellar Purkinje cells are known to be highly vulnerable to neuronal pathology in Niemann-Pick type C (NPC), a disease where widespread white matter changes have also been reported. We sought to determine the relationship between white and grey matter cerebellar changes and clinical variables in NPC. Materials and methods: Ten adult patients with NPC were matched to control subjects (n=27) on age and gender. Patients were rated for symptom duration and severity, degree of ataxia, and were assessed for saccadic eye measures. Cerebellar white and grey matter volumes were automatically segmented using the Freesurfer software package. Results: NPC patients had a significant reduction in both grey and white matter volumes. Volume did not correlate with symptom duration or severity, but did correlate with saccadic gain and ataxia measures. Conclusions: Both cerebellar grey and white matter volume decreases in adult NPC, and these changes are associated with impairments in saccadic gain and in motor control.

Journal of Inherited Metabolic Disease, 2009

We describe the differential presentation of schizophrenia-like psychosis in two siblings with th... more We describe the differential presentation of schizophrenia-like psychosis in two siblings with the Fvariant_ biochemical presentation of adult Niemann-Pick disease type C. The male sibling presented with psychosis at age 16 years and cognitive and motor disturbance at age 25 years, whereas his elder sister, sharing the same mutation but showing less severe biochemical, neuroimaging and ocular motor parameters, presented with a similar schizophrenia-like illness with associated cognitive and motor disturbance at age 31 years. Their illness onset, course and response to treatment mirrors the sex dimorphism seen in schizophrenia, and is suggestive of an interaction between the neurobiology of their metabolic disorder and sex differences in neurodevelopment.

European Journal of Neurology, 2011

Background and purpose: Niemann-Pick disease type C (NPC) is a progressive neurovisceral disorder... more Background and purpose: Niemann-Pick disease type C (NPC) is a progressive neurovisceral disorder associated with dystonia, ataxia and a characteristic gaze palsy. Neuropathological studies have demonstrated brainstem atrophy associated with neuronal inclusions and loss, and neurofibrillary tangles, although it is not known whether this pathology can be detected in vivo or how these changes relate to illness variables, particularly ocular-motor changes. Our aim was to utilize a method for brainstem atrophy, validated in progressive supranuclear palsy (PSP), in a group of adult patients with NPC, and explore its relationship to illness variables and ocularmotor functioning. Methods: We calculated the midbrain and pontine area, and pontine-to-midbrain ratio (PMR) from midsagittal images of 10 adult patients with NPC and 27 age-and gender-matched controls. Measures were correlated with illness variables, and measures of horizontal saccadic functioning. Results: Pontine-to-midbrain ratio was 14% higher in the NPC group, but this difference was not significant. However, PMR showed a significant positive correlation with duration of illness and a measure of illness severity. Furthermore, PMR was significantly negatively correlated with saccadic peak velocity and gain, and self-paced saccadic performance. Conclusions: Pontine-to-midbrain ratio was increased in adult patients with NPC compared to controls, although not to the same degree as previously described in PSP, which also presents with significant gaze palsy. These changes were driven predominantly by progressive midbrain atrophy. The strong correlation with illness and ocular-motor variables suggests that it may be a useful marker for illness progression in NPC.

Brain and Cognition, 2008

The "co-familiality" criterion for an endophenotype has two requirements: (1) clinically unaffect... more The "co-familiality" criterion for an endophenotype has two requirements: (1) clinically unaffected relatives as a group should show both a shift in mean performance and an increase in variance compared with controls;

American Journal of Neuroradiology, 2013

Voxel-based analysis has suggested that deep gray matter rather than cortical regions is initiall... more Voxel-based analysis has suggested that deep gray matter rather than cortical regions is initially affected in adult Niemann-Pick type C. We sought to examine a range of deep gray matter structures in adults with NPC and relate these to clinical variables. Ten adult patients with NPC (18-49 years of age) were compared with 27 age- and sex-matched controls, and subcortical structures were automatically segmented from normalized T1-weighted MR images. Absolute volumes (in cubic millimeters) were generated for a range of deep gray matter structures and were compared between groups and correlated with illness variables. Most structures were smaller in patients with NPC compared with controls. The thalamus, hippocampus, and striatum showed the greatest and most significant reductions, and left hippocampal volume correlated with symptom score and cognition. Vertex analysis of the thalamus, hippocampus, and caudate implicated regions involved in memory, executive function, and motor control. Thalamic and hippocampal reductions may underpin the memory and executive deficits seen in adult NPC. Volume losses in other subcortical regions may also be involved in the characteristic range of motor, psychiatric, and cognitive deficits seen in the disease.

American Journal of Neuroradiology, 2011

BACKGROUND AND PURPOSE: Variable alterations to the structure of the corpus callosum have been de... more BACKGROUND AND PURPOSE: Variable alterations to the structure of the corpus callosum have been described in adults with NPC, a neurometabolic disorder known to result in both white and gray matter pathology. This study sought to examine the structure of the callosum in a group of adult patients with NPC and compared callosal structure with a group of matched controls, and to relate callosal structure with state and trait illness variables.

Background: Niemann-Pick Type C disease (NPC), is an autosomal recessive neurovisceral disorder o... more Background: Niemann-Pick Type C disease (NPC), is an autosomal recessive neurovisceral disorder of lipid metabolism. One characteristic feature of NPC is a vertical supranuclear gaze palsy particularly affecting saccades. However, horizontal saccades are also impaired and as a consequence a parameter related to horizontal peak saccadic velocity was used as an outcome measure in the clinical trial of miglustat, the first drug approved in several jurisdictions for the treatment of NPC. As NPC-related neuropathology is widespread in the brain we examined a wider range of horizontal saccade parameters and to determine whether these showed treatment-related improvement and, if so, if this was maintained over time.