Gain control network conditions in early sensory coding

Gain control is essential for the proper function of any sensory system. However, the precise mechanisms for achieving effective gain control in the brain are unknown. Based on our understanding of the existence and strength of connections in the insect olfactory system, we analyze the conditions that lead to controlled gain in a randomly connected network of excitatory and inhibitory neurons. We consider two scenarios for the variation of input into the system. In the first case, the intensity of the sensory input controls the input currents to a fixed proportion of neurons of the excitatory and inhibitory populations. In the second case, increasing intensity of the sensory stimulus will both, recruit an increasing number of neurons that receive input and change the input current that they receive. Using a mean field approximation for the network activity we derive relationships between the parameters of the network that ensure that the overall level of activity of the excitatory population remains unchanged for increasing intensity of the external stimulation. We find that, first, the main parameters that regulate network gain are the probabilities of connections from the inhibitory population to the excitatory population and of the connections within the inhibitory population. Second, we show that strict gain control is not achievable in a random network in the second case, when the input recruits an increasing number of neurons. Finally, we confirm that the gain control conditions derived from the mean field approximation are valid in simulations of firing rate models and Hodgkin-Huxley conductance based models

Anopheles darlingi polytene chromosomes: revised maps including newly described inversions and evidence for population structure in Manaus

Salivary gland polytene chromosomes of 4th instar Anopheles darlingi Root were examined from multiple locations in the Brazilian Amazon. Minor modifications were made to existing polytene photomaps. These included changes to the breakpoint positions of several previously described paracentric inversions and descriptions of four new paracentric inversions, two on the right arm of chromosome 3 and two on the left arm of chromosome 3 that were found in multiple locations. A total of 18 inversions on the X (n = 1) chromosome, chromosome 2 (n = 7) and 3 (n = 11) were scored for 83 individuals from Manaus, Macapá and Porto Velho municipalities. The frequency of 2Ra inversion karyotypes in Manaus shows significant deficiency of heterozygotes (p < 0.0009). No significant linkage disequilibrium was found between inversions on chromosome 2 and 3. We hypothesize that at least two sympatric subpopulations exist within the An. darlingi population at Manaus based on inversion frequencies

Multicultural mediations, developing world realities: Indians, Koreans and Manila’s entertainment media

In this article, I examine the mediation of multiculturalism in the developing world city of Manila, the Philippines. Drawing on both a thematic analysis of the Manila-centric Philippine entertainment media and six focus group discussions with the city’s local Filipinos, I reveal that this instance of mediation is entangled with the broader discourses of the Philippine postcolonial nationalist project. For one, the mediation of multiculturalism in Manila tends to symbolically marginalize the city’s Indians and Koreans and, in so doing, reinforces existing negative discourses about them. I contend that this is linked to the locals’ preoccupation with establishing a unifying cultural identity that tends to make them elide the issue of their own internal cultural diversity, as well as of the increasing diasporic population of the city. Second, the said mediation also tends to valorize the lighter-skinned Koreans over the darker-skinned Indians. I posit that this is related to how the locals’ discourse of cultural homogeneity has resulted in their continued reluctance to publicly discuss the persistence of their unspoken skin-tone-based racial hierarchy not only of themselves, but also of their cultural others

Manejo de fincas a través de prácticas y tecnologías agroecológicas de adaptación al cambio climático

Orieta el diseño de un proceso de desarrollo productivo, en la producción y aplicación de insumos agroecológicos en fincas, asimismo orienta a más productores y productoras vecinas en el uso de prácticas agroecológicas en la producción agrícola. Toma en cuenta la caracterización del sistema de producción familiar y sus medios de vida