The role of docosahexaenoic acid in retinal function

An important role for docosahexaenoic acid (DHA) within the retina is suggested by its high levels and active conservation in this tissue. Animals raised on n-3-deficient diets have large reductions in retinal DHA levels that are associated with altered retinal function as assessed by the electroretinogram (ERG). Despite two decades of research in this field, little is known about the mechanisms underlying altered retinal function in n-3-deficient animals. The focus of this review is on recent research that has sought to elucidate the role of DHA in retinal function, particularly within the rod photoreceptor outer segments where DHA is found at its highest concentration. An overview is also given of human infant studies that have examined whether a neonatal dietary supply of DHA is required for the normal development of retinal function.     

Reinforced variability decreases with approach to reinforcers.

Anticipation of rewards had different effects on operant variability than on operant repetition. We reinforced variable (VAR) response sequences in groups of rats and pigeons and repetitive (REP) response sequences in separate groups. A fixed number of variations or repetitions was required per food reinforcer (e.g., fixed-ratio 4). Although VAR contingencies resulted in high levels of variability and REP contingencies in high repetition, opposite patterns of performance accuracy were observed as rewards were approached. Likelihood of satisfying REP contingencies increased within the fixed ratio, whereas likelihood of satisfying VAR contingencies decreased. These opposite patterns of accuracy were also generated by conditioned reinforcing stimuli correlated with food. Constraints on variability by proximity to reinforcers may explain some detrimental effects of reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rigid thinking in suicidal individuals.

The folklore hypothesis that suicidal individuals think in a rigid manner was evaluated by the California F Scale and the Rokeach Map Test. They were administered to a suicidal attempt group, a group of psychosomatic patients, and to hospitalized normal Ss. It was found that the suicidal group earned significantly higher California F Scale scores (p     

The effects of panresistant bacteria in cystic fibrosis patients on lung transplant outcome

The number of cystic fibrosis (CF) patients undergoing lung transplant continues to rise as long term survival improves. One major contraindication to this potentially life-saving intervention is infection with multi-drug-resistant bacteria. We undertook this retrospective study in 66 transplanted patients over 6 yr to determine the influence of panresistant bacteria on transplant outcome. The in vitro antibiotic susceptibility pattern of respiratory tract bacteria obtained pre- and/or intraoperatively was used to categorize patients into panresistant (n = 27) (Burkholderia cepacia, n = 6, and Pseudomonas aeruginosa, n = 21) or sensitive (n = 39) groups. Postoperative ventilator days, hospital length of stay, and antibiotic days were similar for both groups (p > 0.2). The incidence of bacterial bronchitis (28% and 33%, respectively) and pneumonia (28% and 38%, respectively) did not differ between these groups (p > 0.2) at 6 mo. Likewise, one-year (81% and 83%, respectively) survival was similar for both groups (p > 0.2). As expected, panresistant B. cepacia patients had a lower 1-yr survival (50% versus 90%, p < 0.05) and had a higher mortality attributable to B. cepacia (50% versus 0%, p < 0.01) compared with panresistant P. aeruginosa patients. Our results indicate that CF patients infected with panresistant P. aeruginosa have similar transplant outcomes as patients with sensitive bacteria and should not be excluded from lung transplant based solely on this criterion.     

Variability is an operant.

In 6 experiments, a total of 7 pigeons were rewarded if their pattern of 8 pecks to left and right response keys during the current trial differed from the patterns in each of the last n trials. In Exps I and II, B. Schwartz's (1980, 1982a) negative findings (variability was not controlled by reinforcement) were compared with the present positive results. In Exp III, n was manipulated, and it was found that Ss generated highly variable patterns even when the current response sequence had to differ from each of the last 50 sequences. In Exp IV, the number of responses per trial was manipulated; variability increased with increasing responses per trial, indicating that the Ss were acting as quasi-random generators. In Exp V, it was shown that for high levels of variability to be engendered, reinforcement had to be contingent on response variability. In a yoked condition, where variability was permitted but not required, little response variability was observed. In Exp VI, stimulus control was demonstrated: Under red lights the Ss generated variable patterns, and under blue lights they repeated a particular fixed pattern. It is concluded that behavioral variability is an operant dimension of behavior controlled by contingent reinforcement. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repressor-sensitizer personality styles and associated levels of verbal ability, social intelligence, sex knowledge, and quantitative ability.

Utilized Byrne's Repression-Sensitization scale to assign 164 male undergraduates to repressor, neutral, or sensitizer groups. Scores from measures of verbal ability, social intelligence, sex knowledge, quantitative ability, and scholastic grades were obtained. Sensitizers, who use such defenses as intellectualization, rumination, and approach, were hypothesized to score higher on selected intellectual measures than repressors who use repression, denial, and avoidance. Results were opposite to those hypothesized, with repressors significantly exceeding sensitizers on 6 of 12 measures, using t tests. Sensitizers did not significantly exceed repressors on any of the measures. When verbal aptitude was held constant through covariance, the groups did not differ. It is concluded that repressors exceed sensitizers on verbal aptitude and that other obtained differences are artifacts of this variable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability and variability in extinction.

Some studies have found that extinction leaves response structures unaltered; others have found that response variability is increased. Responding by Long-Evans rats was extinguished after 3 schedules. In one, reinforcement depended on repetitions of a particular response sequence across 3 operanda. In another, sequences were reinforced only if they varied. In the third, reinforcement was yoked: not contingent upon repetitions or variations. In all cases, rare sequences increased during extinction—variability increased—but the ordering of sequence probabilities was generally unchanged, the most common sequences during reinforcement continuing to be most frequent in extinction. The rats' combination of generally doing what worked before but occasionally doing something very different may maximize the possibility of reinforcement from a previously bountiful source while providing necessary variations for new learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NSF Graduate Fellowship evaluations.

Comments on C. McCauley's (see record 1992-14458-001) criticisms of the 1990 National Science Foundation (NSF) Graduate Fellowship psychology panel for ignoring actuarial procedures (APs). APs correlate predictor measures with outcomes to derive an equation that predicts new outcomes, which could replace individual human judgments in the allocation of fellowships. The author states that APs were used by the NSF, that McCauley only provided partial data in his criticisms, and that a derived score was used as an independent evaluation to increase panel efficiency and as a check to minimize chances of error. The important aspects of actuarial research are not ignored by NSF panels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retinal morphology and visual pigment levels in 6- and 12-month-old rhesus monkeys fed a taurine-free human infant formula

Rhesus monkey infants were raised from birth until 6 or 12 months of age on a taurine-free soy protein-based human infant formula or on the same formula supplemented with taurine. An additional group received taurine-free formula until 6 months and then the supplemented diet from 6 until 12 months. The densities of rod and cone visual pigments were measured by fundus reflectometry at 6 and 12 months, and retinal morphology was then examined by light and electron microscopy. The densities of rhodopsin, measured in the near periphery after a white bleach, and of cone pigment, measured in the macula after a red bleach, were significantly reduced in the taurine-deprived monkeys at 6 months but not at 12 months. The retinas of 6-month-old taurine-deprived infants showed degenerative morphological changes in photoreceptors, particularly in cones in the foveal region, which were somewhat less severe than those seen in a previous study at 3 months of age. The prevalence and degree of these abnormalities continued to decrease with age in taurine-deprived animals, but changes persisted in some animals at 12 months. Recovery was more complete in monkeys reversed to the supplemented diet from 6 to 12 months. Thus, monkey infants are dependent on dietary taurine to maintain normal retinal structure until at least 6 months of age; the effects of taurine deprivation regress spontaneously but incompletely by 12 months.