The registration of spatial information by neurons of the parietal cortex takes on many forms. In most experiments, spatially modulated parietal activity patterns are found to take as their frame of ...reference some part of the body such as the retina. However, recent findings obtained in single neuron recordings from both rat and monkey parietal cortex suggest that the frame of reference utilized by parietal cortex may also be abstract or arbitrary in nature. Evidence in rats comes from work indicating that parietal activity in freely behaving rodents is organized according to the space defined by routes taken through an environment. In monkeys, evidence for an object-centered frame of reference has recently been presented. The present work reviews single neuron recording experiments in parietal cortex of freely behaving rats and considers the potential contribution of parietal cortex in solving navigational tasks. It is proposed that parietal cortex, in interaction with the hippocampus, plays a critical role in the selection of the most appropriate route between two points and, in addition, produces a route-based positional signal capable of guiding sensorimotor transitions.
Parallel recordings of hippocampal principal cells and interneurons were obtained as rats foraged in familiar and adjacent, novel environments. Firing rates of each cell type were assessed as a ...function of spatial location. Many CA1 interneurons exhibited large decreases in activity in the novel compared with the familiar environment. Dentate gyrus interneurons, however, were much more likely to exhibit large increases in firing in the novel environment. Neither effect was correlated with basic interneuron discharge properties such as degree of theta modulation, baseline firing rate or degree of spatially modulated discharge. Both CA1 and dentate gyrus interneuron rate changes extended into regions of the familiar environment bordering the novel environment. Principal cells in CA1 and dentate gyrus exhibited similar patterns of place specific activity each being indicative of incorporation of novel spatial information into the spatial representation of the familiar environment. The data indicate that inhibitory networks in the CA1 and dentate gyrus areas are modulated in a divergent fashion during the acquisition of novel spatial information and that interneuron activities can be used to detect those regions of an environment subject to redistribution of principal cell spatial activity patterns.
Virtual movement of the animal through a given neuron's place field is accompanied by a ramp-like depolarization of the cell's membrane potential that spans the length of that field. ... the ...depolarization envelope carries a theta-frequency rhythm that is much more prominent than when the animal moves outside the place field of the recorded neuron. ... the initial development of the technique in mice suggests that the authors may in the future conduct experiments in genetically modified animals.
Complex behaviors demand temporal coordination among functionally distinct brain regions. The basal forebrain's afferent and efferent structure suggests a capacity for mediating this coordination at ...a large scale. During performance of a spatial orientation task, synaptic activity in this region was dominated by four amplitude-independent oscillations temporally organized by the phase of the slowest, a theta-frequency rhythm. Oscillation amplitudes were also organized by task epoch and positively correlated to the task-related modulation of individual neuron firing rates. For many neurons, spiking was temporally organized through phase precession against theta band field potential oscillations. Theta phase precession advanced in parallel to task progression, rather than absolute spatial location or time. Together, the findings reveal a process by which associative brain regions can integrate independent oscillatory inputs and transform them into sequence-specific, rate-coded outputs that are adaptive to the pace with which organisms interact with their environment.
•High molecular prevalence of Leishmania in Brazilian sand flies.•DNA sequencing confirmed Leishmania infantum in Lutzomyia longipalpis samples.•High-Resolution Melting analysis revealed most ...infected sand flies fed on chicken.•Human blood was found in one Leishmania-negative female sandfly.•Leishmania infantum transmission to humans is an ongoing threat in the studied area.
Leishmaniases are endemic in Brazil, where Leishmania infantum has been detected in humans, dogs, cats, and phlebotomine vectors. Monitoring synanthropic vector populations is critical for leishmaniasis control-surveillance in such transmission-prone areas. Here, a suite of molecular approaches were used to assess Leishmania infection prevalence and to identify blood-meal sources in a large sample of sand flies collected in anthropic environments of a Leishmania-transmission area in Mato Grosso do Sul State (Rio Verde de Mato Grosso municipality), Central-West Brazil. We sampled sand flies monthly (January-June 2014 and 2016) in one peri-domestic site within each of six neighborhoods with recent records of human visceral and/or tegumentary leishmaniasis. kDNA-qPCR plus rDNA ITS-sequencing were used to detect and identify Leishmania in pooled female sand flies. Individual engorged females (n = 58) were used for blood-meal analyses through High-Resolution Melting (HRM) targeting the mtDNA cytb gene. Overall, 90.5% of 420 CDC trap-nights yielded vectors, for a total catch of 24,989 sand flies. We sub-sampled and identified 3088 sand flies of 12 species, including 2775 Lutzomyia longipalpis (the most abundant species at all sampling sites) and 297 Nyssomyia whitmani. Female sand flies (n = 1261) were grouped in 159 pools, of which 92 Lu. longipalpis (minimum infection rate MIR 8%) and 7 Ny. whitmani pools (MIR 7%) were Leishmania kDNA-positive. Most positive Lu. longipalpis were collected in the 2016 rainy season. Sequencing confirmed L. infantum in Lu. longipalpis samples. HRM analyses identified chicken DNA in 57 sand flies (98.3%), 37 of which were Leishmania DNA-positive (64.9%); human blood was found in just one (Leishmania-negative) female. Our data show ongoing risk of L. infantum transmission to humans in the study area, where Leishmania-infected sandfly vectors are common and heavily rely on chicken blood in the peri-domestic environment.
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