Working memory capacity,intelligence, and the magnitude of the attentional blink revisited

The attentional blink (AB) is a well-established phenomenon in the study of attention. This deficit in reporting the second of two targets presented in rapid serial visual presentation when it occurs 200–500 ms after the first is considered to reflect a fundamental limitation in attentional processing. However, we recently reported that some individuals do not show an AB, and presented psychophysiological evidence that target processing differs between blinkers and non-blinkers. One possibility is that non-blinkers may have a larger WM capacity, allowing better attentional control. Here we explore the relation between the magnitude of the AB, general intelligence, and different measures of working memory (WM) and short-term memory (STM) capacity. Surprisingly, no correlation was found between memory capacity measures and AB magnitude, raising doubts about the generalizability of earlier findings of such a relationship.

Progressive behavioral deficits in DJ-1-deficient mice are associated with normal nigrostriatal function

Loss-of-function mutations in the DJ-1 gene account for an autosomal recessive form of Parkinson's disease (PD). To investigate the physiological functions of DJ-1 in vivo, we generated DJ-1 knockout (DJ-1^−/−) mice. Younger (< 1 year) DJ-1^−/− mice were hypoactive and had mild gait abnormalities. Older DJ-1^−/−, however, showed decreased body weight and grip strength and more severe gait irregularities compared to wild-type littermates. The basal level of extracellular dopamine, evoked dopamine release and dopamine receptor D2 sensitivity appeared normal in the striatum of DJ-1^−/− mice, which was consistent with similar results between DJ-1^−/− and controls in behavioral paradigms specific for the dopaminergic system. An examination of spinal cord, nerve and muscle tissues failed to identify any pathological changes that were consistent with the noted motor deficits. Taken together, our findings suggest that loss of DJ-1 leads to progressive behavioral changes without significant alterations in nigrostriatal dopaminergic and spinal motor systems.     

Is breast MRI ever useful in a mammographic screening programme?

OBJECTIVE: To establish the diagnostic impact of breast magnetic resonance imaging (MRI), on the management of cases in our mammographic screening programme. METHODS AND MATERIALS: We analysed the cases examined from July 1997 to December 2000 during which time 44,000 population screening mammograms and 85 MRI studies were undertaken on women identified by computer overlap. The studies were reviewed to find the reason for the MRI study and its diagnostic impact. RESULTS: Of 83 studies analysed, 31 were for recurrence of tumour, 33 in newly diagnosed cancer, 22 to assess extent, 11 to monitor primary chemotherapy. In a small diagnostic subset of 19 cases MRI was used to find or characterize a lesion. The 11 cases in which MRI results caused a measurable beneficial change in management were from the query recurrence and diagnostic groups. In 52 cases from all groups, MR increased diagnostic confidence. In 11 cases MRI results were indeterminate, and in six of these stimulated more studies. CONCLUSION: MRI is an expensive investigation and its use must be justified. There is a limited, but valuable role for breast MRI in selected cases from screening assessment. Misinterpretation of enhancing lesions may generate additional procedures. Diagnostic impact was greatest for the detection of tumour recurrence.     

Galanin transgenic mice display cognitive and neurochemical deficits characteristic of Alzheimer's disease

Galanin is a neuropeptide with multiple inhibitory actions on neurotransmission and memory. In Alzheimer's disease (AD), increased galanin-containing fibers hyperinnervate cholinergic neurons within the basal forebrain in association with a decline in cognition. We generated transgenic mice (GAL-tg) that overexpress galanin under the control of the dopamine beta-hydroxylase promoter to study the neurochemical and behavioral sequelae of a mouse model of galanin overexpression in AD. Overexpression of galanin was associated with a reduction in the number of identifiable neurons producing acetylcholine in the horizontal limb of the diagonal band. Behavioral phenotyping indicated that GAL-tgs displayed normal general health and sensory and motor abilities; however, GAL-tg mice showed selective performance deficits on the Morris spatial navigational task and the social transmission of food preference olfactory memory test. These results suggest that elevated expression of galanin contributes to the neurochemical and cognitive impairments characteristic of AD.     

Effect of phenobarbital on seizure frequency and mortality in childhood cerebral malaria: a randomised, controlled intervention study

This randomized, placebo-controlled study assesses whether a single intramuscular dose of phenobarbital (20 mg/kg) given on admission to Kenyan children with cerebral malaria could lower the frequency of seizures, which complicate cerebral malaria by increasing the risk of death and neurological sequelae. A total of 340 children with cerebral malaria were admitted to the hospital; 170 received phenobarbital and 170 received placebo. The drug was adequately absorbed and well tolerated. Findings revealed a significantly lower frequency of seizures in the phenobarbital group than in the placebo group (18 [11%] vs. 46 [27%] children had 3 or more seizures of any duration; odds ratio (OR), 0.32; 95% confidence interval (CI), 0.18-0.58). However, mortality was doubled (30 [18%] vs. 14 [8%] deaths; OR, 2.39; 95% CI, 1.28-4.64) in the phenobarbital group. In addition, the frequency of respiratory arrest was higher in the phenobarbital group than in the placebo group, and mortality was greatly increased in children who received phenobarbital plus 3 or more doses of diazepam. In conclusion, although the phenobarbital dose of 20 mg/kg given to children with cerebral malaria provides highly effective seizure prophylaxis, an unacceptable increase in mortality is noted; hence, use of this dosage is not recommended.     

Contrasting dynamics in the same plant-herbivore interaction

Long-term studies of two-species interactions under field conditions are unusual; most long-term field studies are of single species dynamics (1-6). Concurrent long-term studies on the dynamics of the same two interacting species in different locations are very rare. This result has led to the tacit assumption that different cases of the same two-species interaction would involve essentially quantitative differences (e.g., context-specific differences in the numeric values of demographic parameters like fecundity or death rates). Here, we show that for one of the best-known two-species systems (ragwort and cinnabar moth), this finding does not hold. The interaction between the plant and its herbivore is fundamentally different in coastal dunes in The Netherlands and in grasslands in Southeast England. In the first case, the dynamics are cyclic and the interaction involves both direct and delayed density dependence; in the second case, the insect has little impact on plant dynamics and there are no time lags in density dependence. The difference is caused by differences in the importance of seed-limitation in plant recruitment in the two locations.     

High VWF, low ADAMTS13, and oral contraceptives increase the risk of ischemic stroke and myocardial infarction in young women

VWF and ADAMTS13 are major determinants of platelet adhesion after vessel injury. In the present study, we aimed to determine whether VWF or ADAMTS13 plasma antigen levels influence the risks of ischemic stroke (IS) or myocardial infarction (MI) in young women and how these risks are affected by oral contraceptive (OC) use. VWF and ADAMTS13 plasma antigen levels were measured in a frequency-matched case-control study of 1018 young (18-49 years) women including 175 IS patients and 205 MI patients. Increasing levels of VWF and decreasing levels of ADAMTS13 were associated with the risk of IS and MI in a dose-dependent manner. Having both high VWF and low ADAMTS13 resulted in an odds ratio (OR) of 6.9 (95% confidence interval [95% CI], 2.0-23.0) for IS and 11.3 (95% CI, 3.6-35.2) for MI. Use of OCs increased the risk of IS and MI associated with high VWF (OR = 12; 95% CI, 5.5-26.2 and OR = 7.5, 95% CI, 3.6-15.7, respectively) and the risk of IS associated with low ADAMTS13 (OR = 5.8, 95% CI, 2.7-12.4). We conclude that high VWF and low ADAMTS13 plasma levels both increase the risk of IS and MI. The risks associated with high VWF or low ADAMTS13 levels are further increased by the use of OCs.