No link between handedness and spatial navigation: evidence from over 400 000 participants in 41 countries.

There is an active debate concerning the association of handedness and spatial ability. Past studies used small sample sizes. Determining the effect of handedness on spatial ability requires a large, cross-cultural sample of participants and a navigation task with real-world validity. Here, we overcome these challenges via the mobile app Sea Hero Quest. We analysed the navigation performance from 422 772 participants from 41 countries and found no reliable evidence for any difference in spatial ability between left- and right-handers across all countries. A small but growing gap in performance appears for participants over 64 years old, with left-handers outperforming right-handers. Further analysis, however, suggests that this gap is most likely due to selection bias. Overall, our study clarifies the factors associated with spatial ability and shows that left-handedness is not associated with either a benefit or a deficit in spatial ability.

Cultural determinants of the gap between self-estimated navigation ability and wayfinding performance: evidence from 46 countries.

Cognitive abilities can vary widely. Some people excel in certain skills, others struggle. However, not all those who describe themselves as gifted are. One possible influence on self-estimates is the surrounding culture. Some cultures may amplify self-assurance and others cultivate humility. Past research has shown that people in different countries can be grouped into a set of consistent cultural clusters with similar values and tendencies, such as attitudes to masculinity or individualism. Here we explored whether such cultural dimensions might relate to the extent to which populations in 46 countries overestimate or underestimate their cognitive abilities in the domain of spatial navigation. Using the Sea Hero Quest navigation test and a large sample (N = 383,187) we found cultural clusters of countries tend to be similar in how they self-rate ability relative to their actual performance. Across the world population sampled, higher self-ratings were associated with better performance. However, at the national level, higher self-ratings as a nation were not associated with better performance as a nation. Germanic and Near East countries were found to be most overconfident in their abilities and Nordic countries to be most under-confident in their abilities. Gender stereotypes may play a role in mediating this pattern, with larger national positive attitudes to male stereotyped roles (Hofstede's masculinity dimension) associated with a greater overconfidence in performance at the national level. We also replicate, with higher precision than prior studies, evidence that older men tend to overestimate their navigation skill more than other groups. These findings give insight into how culture and demographics may impact self-estimates of our abilities.

Entropy and a sub-group of geometric measures of paths predict the navigability of an environment.

Despite extensive research on navigation, it remains unclear which features of an environment predict how difficult it will be to navigate. We analysed 478,170 trajectories from 10,626 participants who navigated 45 virtual environments in the research app-based game Sea Hero Quest. Virtual environments were designed to vary in a range of properties such as their layout, number of goals, visibility (varying fog) and map condition. We calculated 58 spatial measures grouped into four families: task-specific metrics, space syntax configurational metrics, space syntax geometric metrics, and general geometric metrics. We used Lasso, a variable selection method, to select the most predictive measures of navigation difficulty. Geometric features such as entropy, area of navigable space, number of rings and closeness centrality of path networks were among the most significant factors determining the navigational difficulty. By contrast a range of other measures did not predict difficulty, including measures of intelligibility. Unsurprisingly, other task-specific features (e.g. number of destinations) and fog also predicted navigation difficulty. These findings have implications for the study of spatial behaviour in ecological settings, as well as predicting human movements in different settings, such as complex buildings and transport networks and may aid the design of more navigable environments.

Reported sleep duration reveals segmentation of the adult life-course into three phases.

Classically the human life-course is characterized by youth, middle age and old age. A wide range of biological, health and cognitive functions vary across this life-course. Here, using reported sleep duration from 730,187 participants across 63 countries, we find three distinct phases in the adult human life-course: early adulthood (19-33yrs), mid-adulthood (34-53yrs), and late adulthood (54+yrs). They appear stable across culture, gender, education and other demographics. During the third phase, where self-reported sleep duration increases with age, cognitive performance, as measured by spatial navigation, was found to have an inverted u-shape relationship with reported sleep duration: optimal performance peaks at 7 hours reported sleep. World-wide self-reported sleep duration patterns are geographically clustered, and are associated with economy, culture, and latitude.

Entropy of city street networks linked to future spatial navigation ability.

The cultural and geographical properties of the environment have been shown to deeply influence cognition and mental health1-6. Living near green spaces has been found to be strongly beneficial7-11, and urban residence has been associated with a higher risk of some psychiatric disorders12-14-although some studies suggest that dense socioeconomic networks found in larger cities provide a buffer against depression15. However, how the environment in which one grew up affects later cognitive abilities remains poorly understood. Here we used a cognitive task embedded in a video game16 to measure non-verbal spatial navigation ability in 397,162 people from 38 countries across the world. Overall, we found that people who grew up outside cities were better at navigation. More specifically, people were better at navigating in environments that were topologically similar to where they grew up. Growing up in cities with a low street network entropy (for example, Chicago) led to better results at video game levels with a regular layout, whereas growing up outside cities or in cities with a higher street network entropy (for example, Prague) led to better results at more entropic video game levels. This provides evidence of the effect of the environment on human cognition on a global scale, and highlights the importance of urban design in human cognition and brain function.

Aminoglycoside 6'-N-acetyltransferase variants of the Ib type with altered substrate profile in clinical isolates of Enterobacter cloacae and Citrobacter freundii.

Three clinical isolates, Enterobacter cloacae EC1562 and EC1563 and Citrobacter freundii CFr564, displayed an aminoglycoside resistance profile evocative of low-level 6'-N acetyltransferase type II [AAC(6')-II] production, which conferred reduced susceptibility to gentamicin but not to amikacin or isepamicin. Aminoglycoside acetyltransferase assays suggested the synthesis in the three strains of an AAC(6') which acetylated amikacin practically as well as it acetylated gentamicin in vitro. Both compounds, however, as well as isepamicin, retained good bactericidal activity against the three strains. The aac genes were borne by conjugative plasmids (pLMM562 and pLMM564 of ca. 100 kb and pLMM563 of ca. 20 kb). By PCR mapping and nucleotide sequence analysis, an aac(6')-Ib gene was found in each strain upstream of an ant(3")-I gene in a sulI-type integron. The size of the AAC(6')-Ib variant encoded by pLMM562 and pLMM564, AAC(6')-Ib7, was deduced to be 184 (or 177) amino acids long, whereas in pLMM563 a 21-bp duplication allowing the recruitment of a start codon resulted in the translation of a variant, AAC(6')-Ib8, of 196 amino acids, in agreement with size estimates obtained by Western blot analysis. Both variants had at position 119 a serine instead of the leucine typical for the AAC(6')-Ib variants conferring resistance to amikacin. By using methods that predict the secondary structure, these two amino acids appear to condition an alpha-helical structure within a putative aminoglycoside binding domain of AAC(6')-Ib variants.

Carbapenem resistance in a clinical isolate of Citrobacter freundii.

Carbapenem resistance was studied in two sets of Citrobacter freundii strains: (i) strain CFr950, resistant to imipenem (MIC, 16 microg/ml) and isolated in vivo during imipenem therapy, and strain CFr950-Rev, the spontaneous, imipenem-susceptible revertant of CFr950 selected in vitro, and (ii) strains CFr801 and CFr802, two imipenem-resistant mutants selected in vitro from the susceptible clinical isolate CFr800. In all strains, whether they were imipenem-susceptible or -resistant strains, production of the cephalosporinase was derepressed and their Km values for cephaloridine were in the range of 128 to 199 microM. No carbapenemase activity was detected in vitro. The role of cephalosporinase overproduction in the resistance was demonstrated after introduction of the ampD gene which decreased the level of production of cephalosporinase at least 250-fold and resulted in an 8- to 64-fold decrease in the MICs of the carbapenems. The role of reduced permeability in the resistance was suggested by the absence, in CFr950 and CFr802, of two outer membrane proteins (the 42- and 40-kDa putative porins whose levels were considerably decreased in CFr801) and the reappearance of the 42-kDa protein in imipenem-susceptible strain CFr950-Rev. This role was confirmed after introduction of the ompF gene of Escherichia coli into the CFr strains, which resulted in 8- to 16-fold decreases in the MICs of carbapenems for CFr802 and CFr950. We infer from these results that the association of reduced, porin-mediated permeability with high-level cephalosporinase production, observed previously in other gram-negative bacteria, may also confer carbapenem resistance on C. freundii.

Resistance to amikacin and isepamicin in rabbits with experimental endocarditis of an aac(6')-Ib-bearing strain of Klebsiella pneumoniae susceptible in vitro.

The effect of production of the aminoglycoside 6'-N-acetyltransferase [AAC(6')-IB] in Klebsiella pneumoniae on the outcome of amikacin and isepamicin treatment of rabbits with experimental endocarditis was assessed. Isogenic high-level (Hi) and low-level (Lo) AAC(6')-Ib-producing transconjugants (T) were constructed from clinical isolates with plasmid-borne resistance determinants. The MICs of amikacin and isepamicin, their bactericidal effects, and AAC(6')-Ib production appeared to be well correlated among the clinical isolates and the transconjugants. The susceptibility data determined in vitro, with MICs (in micrograms per milliliter) of amikacin and isepamicin for LoT and HiT of 4 and 0.5 and 32 and 8, respectively, were, however, not predictive of the in vivo efficacies of the drugs. While amikacin and isepamicin caused reductions in bacterial densities (log10 CFU per gram of cardiac vegetation) of 5.1 and 4.8 of the fully susceptible recipient strain (MICs of amikacin and isepamicin, 0.5 and 0.25, respectively), the reductions in density of both LoT and HiT caused by the two drugs (2.7 and 2.4 and 2.9 and 2.2, respectively) were only marginally significant, if at all. There was no significant difference (P > 0.05) when the reductions in density of LoT and HiT by either drug were compared or when the efficacies of the two drugs in reducing the density of any strain [non-AAC(6')-producing, LoT, or HiT] were compared (P > 0.5). It is concluded that AAC(6')-Ib in K.pneumoniae, even when produced at a low level and not conferring resistance to amikacin and isepamicin in vitro, compromises the efficacies of both drugs in vivo and possibly does so beyond the experimental model studied here.

Percentages and distributions of teicoplanin- and vancomycin-resistant strains among coagulase-negative staphylococci.

The activities of teicoplanin and vancomycin against 362 coagulase-negative staphylococci were determined by an agar dilution method. At the 4- and 32-micrograms/ml breakpoint levels of the National Committee for Clinical Laboratory Standards, 23.2% of the strains were intermediate and 1.7% were resistant to teicoplanin, in contrast to less than 0.3% intermediate to vancomycin. Resistant strains belonged to the species Staphylococcus epidermidis (74%) and S. haemolyticus (19%).

Bacteriostatic and bactericidal activity of azithromycin against Haemophilus influenzae.

Macrolide antibiotics, commonly used in upper and lower respiratory tract infections, are inconsistently active against Haemophilus influenzae. The new azalide, azithromycin, was compared with erythromycin and roxithromycin against this pathogen. Azithromycin (MIC range 0.06-1 mg/l) was four to eight times more potent than erythromycin (MIC range 0.5-8 mg/l) and roxithromycin (MIC range 0.5-16 mg/l). At 1 mg/l, 100% of the strains of H. influenzae were inhibited by azithromycin compared with 16% with erythromycin and 5% with roxithromycin. Azithromycin exhibited a rapid bactericidal effect, with a 99.9% kill at 4 h. The MBC was equal to or up to four-times greater than the MIC.

In vitro activity of combinations of beta-lactam antibiotics with beta-lactamase inhibitors against cephalosporinase-producing bacteria.

Combinations of different beta-lactam antibiotics, including cefotaxime, with three beta-lactamase inhibitors were tested against cephalosporinase producing bacterial strains. The most significant antagonism was obtained with a combination of clavulanic acid and cefotaxime, while almost no antagonism was observed with sulbactam and tazobactam. In strains belonging to five different species there was a correlation between the levels of cephalosporinase produced after exposure to different concentrations of inhibitors and the MICs of cefotaxime combined with the same concentrations of inhibitors. It is concluded that there is little likelihood of antagonism between beta-lactam antibiotics and sulbactam or tazobactam.