Publications by authors named "Johnny Ng"

Cognitive dysfunction after surgery under general anesthesia is a well-recognized clinical phenomenon in the elderly. Physiological effects of various anesthetic agents have been studied at length. Very little is known about potential effects of anesthesia on brain structure.

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Over the last 15 years, research on canid cognition has revealed that domestic dogs possess a surprising array of complex sociocognitive skills pointing to the possibility that the domestication process might have uniquely altered their brains; however, we know very little about how evolutionary processes (natural or artificial) might have modified underlying neural structure to support species-specific behaviors. Evaluating the degree of cortical folding (i.e.

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All domesticated mammals exhibit marked reductions in overall brain size, however, it is unknown whether the corpus callosum (CC), an integral white matter fiber pathway for interhemispheric cortical communication, is affected by domestication differentially or strictly in coordination with changes in brain size. To answer this question, we used quantitative magnetic resonance imaging to compare the midsagittal cross-sectional areas of the CC in 35 carnivore species, including eight wild canids and 13 domestic dogs. We segmented rostro-caudal regions of interest for the CC and evaluated correlations with brain mass.

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Obsessive-compulsive disorder (OCD) patients show increased insula activation to disgust-inducing images compared to healthy controls (HC). We explored whether this disgust reactivity was also present in the olfactory domain by conducting the first fMRI study of olfaction in OCD. Neural activation in response to pleasant and unpleasant odors (vs.

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We studied the effect of oxygen inhalation during resting state functional MRI scanning in healthy control individuals. We hypothesized that resting state networks would be modified under hyperoxic conditions. Thirty-four normal volunteers were recruited for this study.

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In 2010, a free clinic in northeast Oklahoma City opened its doors and began seeing nonemergent patients. This evidence-based article illustrates the impact of the clinic on its community. It discusses the benefits and financial implications and the operation of the free clinic through contributions and volunteerism, and highlights strengths and limitations.

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Diffuse axonal injury is a common pathological consequence of Traumatic Brain Injury (TBI). Diffusion Tensor Imaging is an ideal technique to study white matter integrity using the Fractional Anisotropy (FA) index which is a measure of axonal integrity and coherence. There have been several reports showing reduced FA in individuals with TBI, which suggest demyelination or reduced fiber density in white matter tracts secondary to injury.

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Recently, the negative effects of hypertension and elevated body mass index on cognitive functioning in schizophrenia have been reported (Friedman et al., 2010). Data suggests that cognitive changes in hypertensive patients from the general population may be mediated, in part, by white matter damage.

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Background: Deficits in cognitive function have been demonstrated among workers chronically exposed to solvents, but the neural basis for these deficits has not been shown.

Objectives: We used functional magnetic resonance imaging (fMRI) to compare pathophysiological changes in brain function between solvent-exposed and control workers.

Methods: Painters, drywall tapers, and carpenters were recruited from the International Union of Painters and Allied Trades, District Council 9 in New York City and District Council 21 in Philadelphia, Pennsylvania, and from the Carpenters Union in New Jersey.

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Purpose: We quantified the performance of time-domain imaging (TDI) and spectral imaging (SI) for fluorescence imaging of quantum dots (QDs) in three distinct imaging instruments: eXplore Optix (TDI, Advanced Research Technologies Inc.), Maestro (SI, CRi Inc.), and IVIS-Spectrum (SI, Caliper Life Sciences Inc.

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Objective: Comparisons of diffusion tensor imaging (DTI) data between first-episode and chronic schizophrenia patients assessed in different studies have led to the suggestion that the decreased fractional anisotropy observed in chronic schizophrenia patients is less pronounced in first-episode patients. However, such comparisons of imaging data generated across studies are susceptible to numerous confounders, which may limit the interpretation of any differences. In order to address these issues and determine whether the DTI abnormalities of chronic schizophrenia are present at illness onset, the authors conducted a DTI investigation of the largest cohort of first-episode schizophrenia patients yet reported in conjunction with a group of chronic schizophrenia patients and healthy subjects for comparison.

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Background: Evidence suggests that white matter integrity may play an underlying pathophysiological role in schizophrenia. N-acetylaspartate (NAA), as measured by Magnetic Resonance Spectroscopy (MRS), is a neuronal marker and is decreased in white matter lesions and regions of axonal loss. It has also been found to be reduced in the prefrontal and temporal regions in patients with schizophrenia.

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We report on the observation of rapid particle acceleration in numerical simulations of relativistic jet-plasma interactions and discuss the underlying mechanisms. The dynamics of a charge-neutral, narrow, electron-positron jet propagating through an unmagnetized electron-ion plasma was investigated using a three-dimensional, electromagnetic, particle-in-cell computer code. The interaction excited magnetic filamentation as well as electrostatic plasma instabilities.

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