The evolution of hyperactivity, impulsivity and cognitive diversity

The evolutionary status of attention deficit/hyperactivity disorder (ADHD) is central to assessments of whether modern society has created it, either physically or socially; and is potentially useful in understanding its neurobiological basis and treatment. The high prevalence of ADHD (5–10%) and its association with the seven-repeat allele of DRD4, which is positively selected in evolution, raise the possibility that ADHD increases the reproductive fitness of the individual, and/or the group. However, previous suggestions of evolutionary roles for ADHD have not accounted for its confinement to a substantial minority. Because one of the key features of ADHD is its diversity, and many benefits of population diversity are well recognized (as in immunity), we study the impact of groups' behavioural diversity on their fitness. Diversity occurs along many dimensions, and for simplicity we choose unpredictability (or variability), excess of which is a well-established characteristic of ADHD. Simulations of the Changing Food group task show that unpredictable behaviour by a minority optimizes results for the group. Characteristics of such group exploration tasks are risk-taking, in which costs are borne mainly by the individual; and information-sharing, in which benefits accrue to the entire group. Hence, this work is closely linked to previous studies of evolved altruism. We conclude that even individually impairing combinations of genes, such as ADHD, can carry specific benefits for society, which can be selected for at that level, rather than being merely genetic coincidences with effects confined to the individual. The social benefits conferred by diversity occur both inside and outside the ‘normal’ range, and these may be distinct. This view has the additional merit of offering explanations for the prevalence, sex and age distribution, severity distribution and heterogeneity of ADHD

Cloridrato de tiletamina associado com cloridrato de zolazepam na tranqüilização e anestesia de calitriquídeos (Mammalia, Primates) Tiletamine hydrochloride in association with zolazepam hydrochloride for the tranquilization and anesthesia of callitrichids

Utilizou-se a associação de cloridrato de tiletamina (125mg) e cloridrato de zolazepam (125mg) diluídos em água destilada (10ml) como tranqüilizante e anestésico em 38 animais pertencentes às espécies Saguinus imperator imperator (N= 21), Saguinus fuscicollis weddeli (N= 15) e Cebuella pygmea (N=2). Indivíduos de ambos os sexos, com pesos entre 130 e 520g, receberam doses de 0,02ml (1,11mg/kg) a 0,15ml (8,33mg/kg) pela via intramuscular. Na maioria dos casos ocorreu anestesia. Os animais foram libertados no mesmo dia da captura, após recuperação pós-anestésica. Não ocorreu efeito colateral aparente sobre os fetos de duas fêmeas gestantes. Apesar da morte de um animal jovem, os resultados foram considerados satisfatórios na tranqüilização e anestesia de calitriquídeos.<br>Tiletamine hydrochloride (125mg) in association with zolazepam hydrochloride (125mg) diluted in distilled water (10ml) were used as tranquilizer and anesthetic in 38 individuals of three species of callitrichids: 21 black-chinned emperor tamarins (Saguinus imperator imperator), 15 saddleback tamarins (Saguinus fuscicollis weddeli) and 2 pygmy marmosets (Cebuella pygmea). Individuals of both sexes that had weighed between 130g and 520g received doses of 0.02ml (1.11mg/kg) to 0.15ml (8.33mg/kg). In most of the cases anesthesia occurred. Marmosets were liberated in the same day of the capture, after we had verified the animal’s rehabilitation. Side effects were not apparent in the fetus of the two pregnant females. Despite the death of an young individual, the results were considered satisfactory to produce tranquillity and anesthesia in callitrichid