Building bridges between neural models and complex decision making behaviour.

Diffusion processes, and their discrete time counterparts, random walk models, have demonstrated an ability to account for a wide range of findings from behavioural decision making for which the purely algebraic and deterministic models often used in economics and psychology cannot account. Recent studies that record neural activations in non-human primates during perceptual decision making tasks have revealed that neural firing rates closely mimic the accumulation of preference theorized by behaviourally-derived diffusion models of decision making. This article bridges the expanse between the neurophysiological and behavioural decision making literatures specifically, decision field theory [Busemeyer, J. R. & Townsend, J. T. (1993). Decision field theory: A dynamic-cognitive approach to decision making in an uncertain environment. Psychological Review, 100, 432-459], a dynamic and stochastic random walk theory of decision making, is presented as a model positioned between lower-level neural activation patterns and more complex notions of decision making found in psychology and economics. Potential neural correlates of this model are proposed, and relevant competing models are also addressed.     

Effect of combined supplementation with vitamin E and alpha-lipoic acid on myocardial performance during in vivo ischaemia-reperfusion

Reactive oxygen species (ROS) contribute significantly to myocardial ischaemia-reperfusion (I-R) injury. Recently the combination of the antioxidants vitamin E (VE) and alpha-lipoic acid (alpha-LA) has been reported to improve cardiac performance and reduce myocardial lipid peroxidation during in vitro I-R. The purpose of these experiments was to investigate the effects of VE and alpha-LA supplementation on cardiac performance, incidence of dysrhythmias and biochemical alterations during an in vivo myocardial I-R insult. Female Sprague-Dawley rats (4-months old) were assigned to one of the two dietary treatments: (1) control diet (CON) or (2) VE and alpha-LA supplementation (ANTIOXID). The CON diet was prepared to meet AIN-93M standards, which contains 75 IU VE kg-1 diet. The ANTIOXID diet contained 10 000 IU VE kg(-1) diet and 1.65 g alpha-LA kg(-1) diet. After the 14-week feeding period, significant differences (P<0.05) existed in mean myocardial VE levels between dietary groups. Animals in each experimental group were subjected to an in vivo I-R protocol which included 25 min of left anterior coronary artery occlusion followed by 10 min of reperfusion. No group differences (P>0.05) existed in cardiac performance (e.g. peak arterial pressure or ventricular work) or the incidence of ventricular dysrhythmias during the I-R protocol. Following I-R, two markers of lipid peroxidation were lower (P<0.05) in the ANTIOXID animals compared with CON. These data indicate that dietary supplementation of the antioxidants, VE and alpha-LA do not influence cardiac performance or the incidence of dysrhythmias but do decrease lipid peroxidation during in vivo I-R in young adult rats.     

Treatment of advanced heart failure

The incidence of chronic heart failure has increased, with a corresponding increase in morbidity and mortality, and has made a substantial financial impact on our society. Improved therapy for heart failure has resulted in a significant prolongation of survival, a decreased number of hospitalizations, and an enhanced quality of life for many patients. It can reasonably be expected, therefore, that adherence to a rational medical regimen for these patients might decrease costs as well. Management of patients with severe heart failure begins with identifying the etiology and educating the patients and their families. Angiotensin-converting enzyme inhibitors are the cornerstone of therapy but only after diagnostic tests are performed to establish the etiology and extent of myocardial dysfunction. Because cardiac transplantation is a therapeutic option for only a limited number of patients, other surgical and medical therapies have to be viewed as the mainstay of a treatment strategy.     

Prevalence of neutralizing antibodies against California and Bunyamwera serogroup viruses in deer from mountainous areas of California

Plaque reduction-serum dilution neutralization was used to evaluate the status of bunyavirus activity in deer in mountainous areas of California. Antibodies against 9 bunyaviruses were measured in 337 mule deer (Odocoileus hemionus hemionus, O. hemionus californicus, and O. hemionus inyoensis) and black-tailed deer (O. hemionus columbianus). More deer from high mountainous areas had neutralizing antibodies against Jamestown Canyon virus than did deer from low mountainous areas (23% vs. 9%; P less than 0.01). This finding is consistent with transmission by snow pool Aedes mosquitoes. Results for Jerry Slough virus were nearly identical to those for Jamestown Canyon virus, which is further evidence that these are strains of the same virus. Neutralizing antibodies against Northway virus were present in 26% of deer from high mountainous areas and 23% of deer from low mountainous areas, suggesting the involvement of a widespread vector, such as Culiseta inornata. Northway virus is not known to occur outside of Alaska and northwestern Canada. Low prevalences of antibodies were detected in deer to California encephalitis, La Crosse, and snowshoe hare viruses of the California serogroup; and Cache Valley, Lokern, and Main Drain viruses of the Bunyamwera serogroup.     

Hip fracture incidence in nursing home residents and community-dwelling older people,Washington State, 1993-1995

OBJECTIVES: To establish and validate a method of linking data from the Minimum Data Set (MDS) and Medicare hospital claims, to estimate hip fracture incidence rates for Medicare beneficiaries aged 65 and older in Washington State, and to compare the incidence rates of hip fractures in nursing home and non-nursing home residents. DESIGN: Retrospective analysis of Medicare population-based enrollment, hospital claims, and nursing home administrative data sets. SETTING: Nursing home and non-nursing home setting. PARTICIPANTS: Medicare beneficiaries in Washington State residing in the community or in skilled nursing facilities. MEASUREMENTS: Crude age- and sex-specific and standardized age- and sex-adjusted hip fracture incidence for persons residing and not residing in nursing homes. RESULTS: From October 1, 1993, through September 30, 1995, 7,812 Medicare beneficiaries aged 65 or older were hospitalized for hip fractures (6,566 fractures for 1,155,234 person-years of exposure in non-nursing home residents and 1,246 fractures for 42,986 person-years of exposure in nursing home residents). The standardized age- and sex-adjusted hip fracture rate of nursing home residents (23.0 per 1,000 person-years) substantially exceeded that of non-nursing home residents (5.7 per 1,000 person-years) (incidence rate ratio = 4.0, 95% confidence interval = 3.7-4.5). CONCLUSION: The incidence of hip fracture in nursing home residents far exceeds that in noninstitutionalized older people. Linkage of MDS and Medicare hospital claims data is a useful tool for epidemiological surveillance regarding events in nursing homes that are likely to result in hospitalization.