Reactive search trajectories.

<p>(A) Examples of <i>sp</i> search trajectories (spirals only, i.e., no Off), medium dose. For a better visualization single paths are plotted in distinct colors (cyan and light blue on top of mostly blue trajectories). The dots on the trajectories indicate pheromone detections. The black dashed line indicates the plume contour (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003861#s4" target="_blank">Methods</a>). (B) Examples of search trajectories including Off zigzagging, medium dose. Red, yellow and pink trajectories use arithmetic spirals (<i>za</i>), bluish trajectories originate from assuming exponential spirals (<i>ze</i>). Identical conventions as in (A). (C and D) Track-angle histogram of <i>sp</i> and <i>za</i> trajectories, respectively, different colors indicate different pheromone doses. (E) Total number of turns for different stimulations, different colors indicate different reactive strategies for the three groups of pheromone doses, identical conventions as in Fig. 3.</p

Experimental robotic trials.

<p>Experimental robotic trials.</p

Success rates, trajectory lengths, and deviation from the optimal path.

<p>(A) Success rates of reactive search strategies, different colors indicate different strategies (legend in C), grouping indicates different stimulation doses (three doses plus no stimulation). (B) Success rates of cognitive searching with infotaxis (three doses plus no stimulation). (C) Trajectory lengths of reactive search strategies, different colors indicate different strategies, grouping indicates different stimulation doses. (D) Trajectory lengths of cognitive searching with infotaxis (three doses plus no stimulation). (E) Schematic drawing to explain the measure: the average of horizontal deviations (Xi) from trajectory to shortest path between start and source. (F) Deviation from the optimal path () for reactive searching, different colors indicate different reactive strategies for the three groups of pheromone doses. (G) Deviation from the optimal path () for cognitive searching (three doses plus no stimulation). Box plots are explained in the <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003861#s4" target="_blank">Methods</a>, part 2, the numbers indicate mean standard deviation.</p

Reactive search strategies and their biological motivation.

<p>(A) MGC recordings for pheromone stimulation: spike times for seven trials of one neuron and the corresponding average firing rate over time (Peri-Stimulus-Time-Histogram): inhibition separates the On from the Off response which smoothly decreases to baseline firing (Bl). (B) Analysis of MGC recordings of multiphasic neurons: Calculating the regularity () and reliability () over time exhibits an Off phase, whereas Off and baseline firing show uniformly low synchrony values (). Dotted black lines represent single neuron trials, the red line gives the averages. (C) Analysis of MGC recordings of monophasic neurons: neither synchrony nor regularity nor reliability over time exhibit any Off phase. Dotted black lines represent single neuron trials, the blue line gives the averages. (Right side: za, ze, sp) Schematic representation of the corresponding movement sequences: Bl spiraling, On upwind surge, and Off zigzagging (if considered) which are combined into three search strategies, <i>sp</i>, <i>za</i>, and <i>ze</i>.</p

Experimental set-up of the cyborg's search task.

<p>(A) Schematic general set-up: the cyborg starts 2 m from the pheromone source in a 2.54 m region. A fan provides a wind blowing from the top (towards the cyborg). (B) Photo of our cyborg: a Khepera III robot with a moth fixed in a styrofoam roll. Zoom-in 1: top of the styrofoam roll with the insect's head and the two antennae on the outside. Zoom-in 2: one antenna enters the tip of a glass electrode. Photographs by H. Raguet — INRIA.</p

Cognitive search trajectories obtained using infotaxis.

<p>(A) Example <i>it</i> trajectories for no stimulation (green, left), minimum (dark green, middle) and medium (cyan, right) stimulation doses. The dots on the trajectories indicate pheromone detections. The black dashed line indicates the plume contour (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003861#s4" target="_blank">Methods</a>). (B) Total number of turns in <i>it</i> trajectories for different stimulations. Identical conventions as in Fig. 3. (C) Track-angle histograms of <i>it</i> trajectories, different colors indicate different doses. (D) Total number of detections measured during reactive (<i>sp</i>, <i>za</i>, <i>ze</i>) and cognitive (<i>it</i>) searching using three stimulation doses and no stimulation. Identical conventions as in Fig. 3.</p

Neuronal coding of time sub-regions of turbulent stimuli analyzed as a function of pheromone load and distance.

<p>(A) Analysis of olfactory coding in ORNs as a function of pheromone load. Left: coding during the 4 sub-regions described in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005870#pcbi.1005870.g008" target="_blank">Fig 8A</a> analyzed for each pheromone load using the same analysis as in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005870#pcbi.1005870.g008" target="_blank">Fig 8E</a>. Plot shows median values of correlation coefficients and bootstrap confidence interval. Colors code for pheromone load. Middle and right: same analysis as in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005870#pcbi.1005870.g008" target="_blank">Fig 8G and 8H</a>, but ORN data are subdivided in different pheromone loads. Middle: coding of onset of puffs depends on time delay from the end of the preceding puff and on pheromone load. Right: coding of offset of puffs depends on time delay from the end of the preceding puff and on pheromone load. (B) Sub-region analysis of olfactory coding in ORNs as a function of distance. Same conventions as in (A), but ORN data are subdivided in different simulated distances. (C) Same analysis as in (B) but from the subpopulation of ORNs stimulated with pheromone loads of 10⁻⁵ and 10⁻⁴ ng. (D) Sub-region analysis of olfactory coding in PNs as a function of distance. Same conventions as in (A), but PN data are subdivided in different distances.</p

Survivorship of the distribution models fitted to the incubation period data by host age.

<p>Gamma (blue line) Lognormal (green), Weibull (purple), and estimated non-parametric Kaplan-Meier (black) survival function. Age of host plants at inoculation: (A) 18 days (182°C.days), (B) 32 days (359°C.days), (C) 46 days (542°C.days), (D) 60 days (607°C.days), (E) 74 days (811°C.days), (F) 88 days (1053°C.days), (G) 102 days (1303°C.days), (H) 116 days (1545°C.days),and (I) 130 days (1764°C.days).</p

Coefficients of determination <i>R</i>^<i>2</i> between predictions and measured firing rates for the L-N model used in this work and several modified L-N models.

<p>All modification of the model significantly decreased its performance in predicting firing rates (Wilcoxon’s signed rank tests).</p

Neuronal coding varies with time sub-regions during turbulent stimuli.

<p>(A) Four different sub-regions of stimulus sequences were defined with (a) onset of puffs, (b) end of long puffs, (c) offset of puffs and (d) end of long blanks; see text for detailed definition. (B) (ORNs and in dotted grey the subpopulation of ORNs stimulated with pheromone loads of 10^-5 and 10⁻⁴ ng) and (C) (PNs): median values and bootstrap confidence intervals (95%) of firing rate in the 4 sub-regions. (D) Correlation coefficient between consecutive responses of PNs to a sequence turbulent stimuli for the 4 sub-regions defined in (A). Distance was 16 m. Cell number = 13. For each cell, 4 grey dots joined by a grey line represent the median values of correlation coefficients θ during sub-regions. Black line joins the median values. Bottom: dual tests between sub-regions (*: p<0.05, **: p<0.01, ***: p<0.001, n.s.: non-significant, Wilcoxon’s signed rank tests). (E) Correlation coefficient between L-N prediction and ORN responses for the 4 sub-regions. Responses to all distances and doses are pulled together. Same conventions as in (D). (F) Correlation coefficient between L-N prediction and PN responses for the 4 sub-regions. Same conventions as in (D). (G) Correlation coefficient between L-N prediction and measured responses during the onset of puffs depends on the time delay from the end of the preceding puff. Plot shows median values and bootstrap confidence intervals. Grey: ORNs, dotted grey: subpopulation of ORNs stimulated with pheromone loads of 10⁻⁵ and 10⁻⁴ ng, black: PNs. Both for ORNs and for PNs, values with the same letters are not statistically different within a set of neurons (Wilcoxon’s signed rank test, p>0.05). (H) Correlation coefficient at the end of puffs depends on the duration of the preceding puff. Same convention as in (G).</p