Reproductive performance of pheasant breeder hens.
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Age Factors↗
Biomedical subjects
L T Smith
Publications and source records attributed to L T Smith.
Alcoholism and family history of alcoholism: effects on visual and auditory event-related potentials.
In a dual-modality paradigm, visual and auditory event-related potentials were elicited in 40 alcoholic men and 30 controls, equated with the alcoholics on age and education. Half of each group had first-degree relatives who were alcoholic (family history positive). The amplitude of the visual N1 component was reduced among the alcoholics, but their auditory N1 amplitudes were normal. Average N1 amplitudes were also smaller in the family history positive subjects but this effect was significant only for auditory stimuli. Alcoholics showed reduced average P3 amplitudes to both visual and auditory signals, particularly in the family history positive group. Clearly, stratification by family history is useful for ascertainment of ERP variation among alcoholics. There were no effects on P3 latency. Among several possible explanations of P3 deficits in alcoholics, two are particularly interesting: (1) alcoholics cannot mobilize sufficient processing resources in the service of effortful cognitive functions; (2) alcoholics, being poorly motivated, apply insufficient effort to cognitive tasks. An experiment designed to test these hypotheses is described.
Adult↗
The influence of alcohol and sleep deprivation on stimulus evaluation.
The effects of alcohol and sleep deprivation on choice reaction time (RT) as a function of stimulus intensity, stimulus quality, and response compatibility were investigated. Fifty-four male subjects were assigned to one of three levels of alcohol (0.00, 0.07, or 0.10 BAC), and one of two levels of sleep deprivation (0 or 24 h). Stimulus intensity, stimulus quality, and response compatibility were varied (high or low), with RTs identified according to time on task. Significant main effects of each of the stimulus variables were present in baseline analysis, with low-level conditions producing longer RTs. Alcohol produced an overall slowing of RT. The combination of both treatments led to larger increases in RT for low stimulus quality. Sleep deprivation increased RT for high stimulus intensity. Alcohol increased RT for low stimulus intensity, but only when subjects were not sleep deprived. These results imply higher risk with degraded stimulus conditions, e.g., driving in settings of low visibility or at night.
Adult↗
ERP responses to target and nontarget visual stimuli in alcoholics from VA and community treatment programs.
This study had three aims: 1) to cross-validate previously reported findings that sober alcoholics compared to nonalcoholic peers have reduced ERP P300 amplitudes to visual target stimuli at the Pz electrode; 2) to test the hypothesis that alcoholics from VA Hospital treatment programs will manifest more ERP indications of brain dysfunction than peer alcoholics from community treatment programs (paralleling our neuropsychological findings in these samples); and 3) to explore differences among the groups in ERP responses to the little-studied nontarget stimuli. Nineteen VA alcoholics, 32 community alcoholics, and 24 peer community controls were given a visual "oddball" stimulus task. The total group of alcoholics had significantly lower P300 amplitudes than controls for target stimuli at the Pz electrode but VA and community alcoholic subgroups did not differ. There were no latency differences between or among the groups. On the nontarget stimuli, alcoholics had significantly higher P100 and lower N100 amplitudes than the controls at all three scored electrodes (Fz, Cz, and Pz). We conclude that cross-validation of reduced P300 amplitudes at Pz in sober alcoholics was obtained but that differences in severity of brain dysfunction, at least as measured by neuropsychological test performance, cannot account for alcoholics' ERP changes relative to controls. Finally, our data suggest that ERP changes to nontarget visual stimuli should be investigated in addition to the more traditional ERP measures to target stimuli.
Adult↗
70+ and going strong. A Hopi pioneer in nursing. Interview by Eileen M. Sullivan.
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Arizona↗
Mechanical properties of new denture resins polymerized by visible light, heat, and microwave energy.
Properties of seven newer resins polymerized using a water bath, microwave energy, or by visible light were measured. Generally, the new resins were harder and less flexible but had lower impact strength than did the heat-polymerized, rubber-modified resin (Lucitone). The light-activated urethane dimethacrylate resin (Triad) was the least flexible. Microwave polymerization improved the modulus of elasticity of two resins, decreased the impact strength of one, and had little effect on the properties of two other resins.
Acrylic Resins↗
In vitro properties of light-polymerized reline materials.
One premixed and three powder-liquid light-polymerized, hard denture reline materials were evaluated for Knoop hardness, transverse strength, and tensile strength when bonded to a heat-activated denture resin. The chemical compositions of the components of the reline materials were analyzed. The premixed light-activated liner was harder, had a higher tensile bond strength to the heat-activated denture resin, and was somewhat stronger than the power-liquid reline materials. Properties of the resins were related to their compositions.
Acrylic Resins↗