Attractiveness of black Shannon trap for phlebotomines

A white Shannon-type trap was used for captures of female sand flies in the search for natural infection with flagellates, however, due to its low productivity and as a large number of phlebotomines settled on the researchers' black clothes, we decided to compare the relative attractiveness of black and white Shannon-type traps for sand flies. Several pairs of black and white traps were placed side by side in front of caves in four areas in the Serra da Bodoquena, Bonito county, State of Mato Grosso do Sul, Brazil, for a total of 12 observations and 44 h of capture. The experiment resulted in 889 phlebotomines captured, 801 on the black and 88 on the white trap, representing 13 species. The hourly Williams' means were 8.67 and 1.24, respectively, and the black/white ratio was 7.0:1.0. Lutzomyia almerioi, an anthropophilic species closely associated with caves, was predominant (89%). Only two other species, Nyssomyia whitmani and Psathyromyia punctigeniculata, also anthropophilic, were significantly attracted to the black rather than to the white trap (chi2 test; p <= 0.01). The difference between the diversity index of the two traps was not significant at level 0.05. The black trap in these circumstances was much more productive than the white, especially for anthropophilic species

Cortical population activity within a preserved neural manifold underlies multiple motor behaviors

Populations of cortical neurons flexibly perform different functions; for the primary motor cortex (M1) this means a rich repertoire of motor behaviors. We investigate the flexibility of M1 movement control by analyzing neural population activity during a variety of skilled wrist and reach-to-grasp tasks. We compare across tasks the neural modes that capture dominant neural covariance patterns during each task. While each task requires different patterns of muscle and single unit activity, we find unexpected similarities at the neural population level: the structure and activity of the neural modes is largely preserved across tasks. Furthermore, we find two sets of neural modes with task-independent activity that capture, respectively, generic temporal features of the set of tasks and a task-independent mapping onto muscle activity. This system of flexibly combined, well-preserved neural modes may underlie the ability of M1 to learn and generate a wide-ranging behavioral repertoire.This work was supported in part by Grant FP7-PEOPLE-2013-IOF-627384 from the Commission of the European Union (J.A.G.), by Grant F31-NS092356 from the National Institute of Neurological Disorder and Stroke and Grant T32-HD07418 from the National Center for Medical Rehabilitation Research (M.G.P.), by Grant DGE-1324585 from the National Science Foundation (S.N.N.), by Grant 22343 from the Fonds de Recherche du Québec–Santé (C.E.), and by Grant NS053603 from the National Institute of Neurological Disorder and Stroke (S.A.S. and L.E.M.).Peer reviewe

Representation of Stimulus Speed and Direction in Vibrissal-Sensitive Regions of the Trigeminal Nuclei: A Comparison of Single Unit and Population Responses

<div><p>The rat vibrissal (whisker) system is one of the oldest and most important models for the study of active tactile sensing and sensorimotor integration. It is well established that primary sensory neurons in the trigeminal ganglion respond to deflections of one and only one whisker, and that these neurons are strongly tuned for both the speed and direction of individual whisker deflections. During active whisking behavior, however, multiple whiskers will be deflected simultaneously. Very little is known about how neurons at central levels of the trigeminal pathway integrate direction and speed information across multiple whiskers. In the present work, we investigated speed and direction coding in the trigeminal brainstem nuclei, the first stage of neural processing that exhibits multi-whisker receptive fields. Specifically, we recorded both single-unit spikes and local field potentials from fifteen sites in spinal trigeminal nucleus interpolaris and oralis while systematically varying the speed and direction of coherent whisker deflections delivered across the whisker array. For 12/15 neurons, spike rate was higher when the whisker array was stimulated from caudal to rostral rather than rostral to caudal. In addition, 10/15 neurons exhibited higher firing rates for slower stimulus speeds. Interestingly, using a simple decoding strategy for the local field potentials and spike trains, classification of speed and direction was higher for field potentials than for single unit spike trains, suggesting that the field potential is a robust reflection of population activity. Taken together, these results point to the idea that population responses in these brainstem regions in the awake animal will be strongest during behaviors that stimulate a population of whiskers with a directionally coherent motion.</p></div

This figure shows the result of a template-matching classification method using the broad-band local field potentials.

<p>Using a cross-validation approach for each neuron, the training data (consisting of the raw microelectrode recording filtered between 1 and 10000 Hz) was used to estimate a template for each experimental condition. The test data were then compared to each template and the log likelihood calculated. To make classification asynchronous, the template was tested at different lags and the lowest error selected for that condition. The experimental condition with the lowest difference was used to classify the test data. Panel A shows the template waveforms for an example recording site. The templates are very distinct, with the standard deviation showing a relatively low trial-to-trial variability. Panel B shows the average confusion matrix for the template classification. The numbers in Panel B are the per-condition probability of correct classification.</p

Percentage of recording sites with a significant tuning to speed, direction, or both as determined by an ANOVA analysis of signal power in different frequency bands.

<p>Average power in each band was computed from the output from a bank of bandpass filters and significance levels were set at <i>p</i> < 0.05. (A) Percentage of recording sites with a significant tuning to speed or direction. Several bands driven by multi-unit activity (1,000–3,000 Hz, 1,000–5,000 Hz) are sensitive to both speed and direction. (B) Percentage of recording sites with significant tuning to both speed and direction. In several bands driven by multi-unit activity (1,000–3,000 Hz, 1,000–5,000 Hz) more than 80% of recording sites are sensitive to both speed and direction. In contrast, 66% of single unit spike rates were sensitive to both conditions.</p

This figure shows the results of a classification scheme using the spike train from a single unit.

<p>Using a cross-validation approach, the training data for each unit was used to calculate the PSTH. This was normalized to get the probability of firing a spike in each bin. For the test spike train, the probability of observing the spike train given each condition was calculated, assuming independent probabilities of spiking in each time bin. This was repeated for different lags and the highest probability selected for that condition. The condition with the highest probability was used to classify the test spike train (a maximum likelihood approach). Panel A shows the normalized PSTHs for an example unit. Panel B shows the average confusion matrix over all units. The average probability of correct classification is lower than when using the LFPs. Although not necessarily indicative of how the neural system decodes these neural responses, these results, along with <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158399#pone.0158399.g005" target="_blank">Fig 5</a>, suggest that the population response is more robust than the response of a single unit.</p