Alcohol consumption, executive function and risky decision making

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on December 29, 2009).Thesis advisor: Dr. Bruce D. Bartholow.M.A. University of Missouri--Columbia 2009.Previous research has shown that alcohol intoxication can adversely affect behavior by impairing higher cognitive function (e.g., Giancola, 2000) and can lead to increased risk-taking (Leigh, 1999) via impaired executive control. The purpose of this project was to assess the degree to which individual differences in interference control, including neural measures, are associated with self-reported risk-taking behaviors and whether these behaviors are moderated by alcohol intoxication. Participants were 96 male and female adults ages 21-35. Ps completed several self-report measures of risky behavior and executive function before being assigned to one of three beverage conditions: a no-alcohol control beverage, an active placebo beverage, or an alcohol beverage (1.0 g/kg ethanol). They then engaged in a laboratory cognitive control (flanker) task while their EEG (electroencephalogram) was recorded. This research suggests that effects of alcohol on the relationship between neural measures of cognitive control, task performance and self-reported real world risk behavior may be influenced more by alcohol use expectancy than by actual alcohol consumption.Includes bibliographical references

To sleep, perchance to decide : the effect of sleep deprivation on error reactivity

Title from PDF of title page (University of Missouri--Columbia, viewed on May 29, 2012).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Bruce D. BartholowVita.Ph.D. University of Missouri-Columbia 2011.Previous research has shown a host cognitive decrements that result from sleep deprivation including impaired executive function and slowed reaction time (see Durmer & Dinges, 2005). The focus of this research is to understand the effects of sleep deprivation on performance monitoring and adjustment. Participants were 42 male and female students, ages 18-27. Once a participant qualified during a phone screening-interview by reporting being in good health they were assigned to one of two conditions: the 8-hour sleep condition or the 4-hour sleep condition. In the laboratory, Ps completed self-report measures of sleep habits. They then engaged in a cognitive task (the Weapons Identification Task) while their electroencephalogram (EEG) was recorded. Results showed a slowed response in the 4-hour sleep group compared to the 8-hour group. Sleep deprived participants also struggled to respond accurately to stereotype inconsistent trials. Furthermore, those in the 4-hour group were less likely to correctly judge the accuracy of their responses. There appeared to be an effect of Sleep Group on ERN responses, however number of hours of sleep did not appear to have an effect on Pe responses. Overall, the results of this experiment point to the possibility that duration of sleep affects error processing. However, the pattern of effects was not entirely clear, thus results should be considered preliminary.Includes bibliographical reference

Electrophysiological evidence of alcohol-related attentional bias in social drinkers low in alcohol sensitivity.

Low sensitivity (LS) to the acute effects of alcohol is a known risk-factor for alcoholism. However, little is known concerning potential information-processing routes by which this risk factor might contribute to increased drinking. We tested the hypothesis that LS participants would show biased attention to alcohol cues, compared to their high-sensitivity (HS) counterparts. Participants performed a task in which alcoholic and nonalcoholic beverage cues were presented bilaterally followed by a target that required categorization by color. Response times were faster for targets appearing in alcohol-cued than nonalcohol-cued locations for LS but not for HS participants. Event-related potential markers of early attention orienting (P1 amplitude) and subsequent attention reorienting (ipsilateral invalid negativity [IIN] amplitude) indicated preferential selective attention to alcohol-cued locations among LS individuals. Controlling for recent drinking and family history of alcoholism did not affect these patterns, except that among HS participants relatively heavy recent drinking was associated with difficulty reorienting attention away from alcohol-cued locations. These findings suggest a potential information-processing bias through which low sensitivity could lead to heavy alcohol involvement

Possible thermochemical disequilibrium in the atmosphere of the exoplanet GJ 436b

The nearby extrasolar planet GJ 436b--which has been labelled as a 'hot Neptune'--reveals itself by the dimming of light as it crosses in front of and behind its parent star as seen from Earth. Respectively known as the primary transit and secondary eclipse, the former constrains the planet's radius and mass, and the latter constrains the planet's temperature and, with measurements at multiple wavelengths, its atmospheric composition. Previous work using transmission spectroscopy failed to detect the 1.4-\mu m water vapour band, leaving the planet's atmospheric composition poorly constrained. Here we report the detection of planetary thermal emission from the dayside of GJ 436b at multiple infrared wavelengths during the secondary eclipse. The best-fit compositional models contain a high CO abundance and a substantial methane (CH4) deficiency relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere. Moreover, we report the presence of some H2O and traces of CO2. Because CH4 is expected to be the dominant carbon-bearing species, disequilibrium processes such as vertical mixing and polymerization of methane into substances such as ethylene may be required to explain the hot Neptune's small CH4-to-CO ratio, which is at least 10^5 times smaller than predicted

Thermal Emission of WASP-14b Revealed with Three Spitzer Eclipses

Exoplanet WASP-14b is a highly irradiated, transiting hot Jupiter. Joshi et al. calculate an equilibrium temperature Teq of 1866 K for zero albedo and reemission from the entire planet, a mass of 7.3 +/- 0.5 Jupiter masses and a radius of 1.28 +/- 0.08 Jupiter radii. Its mean density of 4.6 g/cm3 is one of the highest known for planets with periods less than 3 days. We obtained three secondary eclipse light curves with the Spitzer Space Telescope. The eclipse depths from the best jointly fit model are $0.224\%$ +/- $0.018\%$ at 4.5 {\mu}m and $0.181\%$ +/- $0.022\%$ at 8.0 {\mu}m. The corresponding brightness temperatures are 2212 +/- 94 K and 1590 +/- 116 K. A slight ambiguity between systematic models suggests a conservative 3.6 {\mu}m eclipse depth of $0.19\%$ +/- $0.01\%$ and brightness temperature of 2242 +/- 55 K. Although extremely irradiated, WASP-14b does not show any distinct evidence of a thermal inversion. In addition, the present data nominally favor models with day night energy redistribution less than $~30\%$. The current data are generally consistent with oxygen-rich as well as carbon-rich compositions, although an oxygen-rich composition provides a marginally better fit. We confirm a significant eccentricity of e = 0.087 +/- 0.002 and refine other orbital parameters.Comment: 16 pages, 16 figure

High C/O Chemistry and Weak Thermal Inversion in the Extremely Irradiated Atmosphere of Exoplanet WASP-12b

The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior as opposed to the silicate-dominated composition as found on Earth; the solar C/O is 0.54. Theory, shows that high C/O leads to a diversity of carbon-rich planets that can have very different interiors and atmospheres from those in the solar system. Here we report the detection of C/O greater than or equal to 1 in a planetary atmosphere. The transiting hot Jupiter WASP-12b has a dayside atmosphere depleted in water vapour and enhanced in methane by over two orders of magnitude compared to a solar-abundance chemical equilibrium model at the expected temperatures. The observed concentrations of the prominent molecules CO, CH4, and H2O are consistent with theoretical expectations for an atmosphere with the observed C/O = 1. The C/O ratios are not known for giant planets in the solar system, although they are expected to equal the solar value. If high C/O ratios are common, then extrasolar planets are likely very different in interior composition, and formed very differently, from expectations based on solar composition, potentially explaining the large diversity in observed radii. We also find that the extremely irradiated atmosphere (greater than 2500 K) of WASP-12b lacks a prominent thermal inversion, or a stratosphere, and has very efficient day-night energy circulation. The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres