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1.
PLoS Comput Biol ; 16(1): e1007402, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31978043

RESUMO

Quantification of behaviour is essential for biology. Since the whisker system is a popular model, it is important to have methods for measuring whisker movements from behaving animals. Here, we developed a high-speed imaging system that measures whisker movements simultaneously from two vantage points. We developed a whisker tracker algorithm that automatically reconstructs 3D whisker information directly from the 'stereo' video data. The tracker is controlled via a Graphical User Interface that also allows user-friendly curation. The algorithm tracks whiskers, by fitting a 3D Bezier curve to the basal section of each target whisker. By using prior knowledge of natural whisker motion and natural whisker shape to constrain the fits and by minimising the number of fitted parameters, the algorithm is able to track multiple whiskers in parallel with low error rate. We used the output of the tracker to produce a 3D description of each tracked whisker, including its 3D orientation and 3D shape, as well as bending-related mechanical force. In conclusion, we present a non-invasive, automatic system to track whiskers in 3D from high-speed video, creating the opportunity for comprehensive 3D analysis of sensorimotor behaviour and its neural basis.


Assuntos
Imageamento Tridimensional/métodos , Vibrissas/diagnóstico por imagem , Vibrissas/fisiologia , Algoritmos , Animais , Fenômenos Biomecânicos/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL
2.
Nature ; 570(7760): 167-168, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31190015
3.
Nat Commun ; 10(1): 2304, 2019 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-31127100

RESUMO

A central problem in speciation is the origin and mechanisms of reproductive barriers that block gene flow between sympatric populations. Wind-pollinated plant species that flower in synchrony with one another rely on post-pollination interactions to maintain reproductive isolation. In some locations in Mexico, sympatric populations of domesticated maize and annual teosinte grow in intimate associate and flower synchronously, but rarely produce hybrids. This trait is typically conferred by a single haplotype, Teosinte crossing barrier1-s. Here, we show that the Teosinte crossing barrier1-s haplotype contains a pistil-expressed, potential speciation gene, encoding a pectin methylesterase homolog. The modification of the pollen tube cell wall by the pistil, then, is likely a key mechanism for pollen rejection in Zea and may represent a general mechanism for reproductive isolation in grasses.


Assuntos
Hidrolases de Éster Carboxílico/genética , Melhoramento Vegetal , Proteínas de Plantas/genética , Isolamento Reprodutivo , Zea mays/genética , Hidrolases de Éster Carboxílico/metabolismo , Cruzamentos Genéticos , Especiação Genética , Mutação , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Tubo Polínico/genética , Tubo Polínico/metabolismo , Simpatria/genética
4.
J Neurosci ; 39(20): 3921-3933, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30850514

RESUMO

Perceptual decision making is an active process where animals move their sense organs to extract task-relevant information. To investigate how the brain translates sensory input into decisions during active sensation, we developed a mouse active touch task where the mechanosensory input can be precisely measured and that challenges animals to use multiple mechanosensory cues. Male mice were trained to localize a pole using a single whisker and to report their decision by selecting one of three choices. Using high-speed imaging and machine vision, we estimated whisker-object mechanical forces at millisecond resolution. Mice solved the task by a sensory-motor strategy where both the strength and direction of whisker bending were informative cues to pole location. We found competing influences of immediate sensory input and choice memory on mouse choice. On correct trials, choice could be predicted from the direction and strength of whisker bending, but not from previous choice. In contrast, on error trials, choice could be predicted from previous choice but not from whisker bending. This study shows that animal choices during active tactile decision making can be predicted from mechanosensory and choice-memory signals, and provides a new task well suited for the future study of the neural basis of active perceptual decisions.SIGNIFICANCE STATEMENT Due to the difficulty of measuring the sensory input to moving sense organs, active perceptual decision making remains poorly understood. The whisker system provides a way forward since it is now possible to measure the mechanical forces due to whisker-object contact during behavior. Here we train mice in a novel behavioral task that challenges them to use rich mechanosensory cues but can be performed using one whisker and enables task-relevant mechanical forces to be precisely estimated. This approach enables rigorous study of how sensory cues translate into action during active, perceptual decision making. Our findings provide new insight into active touch and how sensory/internal signals interact to determine behavioral choices.

5.
Neuroscience ; 368: 95-108, 2018 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28843998

RESUMO

A fundamental question in the investigation of any sensory system is what physical signals drive its sensory neurons during natural behavior. Surprisingly, in the whisker system, it is only recently that answers to this question have emerged. Here, we review the key developments, focussing mainly on the first stage of the ascending pathway - the primary whisker afferents (PWAs). We first consider a biomechanical framework, which describes the fundamental mechanical forces acting on the whiskers during active sensation. We then discuss technical progress that has allowed such mechanical variables to be estimated in awake, behaving animals. We discuss past electrophysiological evidence concerning how PWAs function and reinterpret it within the biomechanical framework. Finally, we consider recent studies of PWAs in awake, behaving animals and compare the results to related studies of the cortex. We argue that understanding 'what the whiskers tell the brain' sheds valuable light on the computational functions of downstream neural circuits, in particular, the barrel cortex.


Assuntos
Vias Aferentes/fisiologia , Fenômenos Biomecânicos/fisiologia , Córtex Somatossensorial/fisiologia , Percepção do Tato/fisiologia , Gânglio Trigeminal/fisiologia , Vibrissas/fisiologia , Animais
9.
Faraday Discuss ; 200: 621-637, 2017 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-28608899

RESUMO

Low cost air pollution sensors have substantial potential for atmospheric research and for the applied control of pollution in the urban environment, including more localized warnings to the public. The current generation of single-chemical gas sensors experience degrees of interference from other co-pollutants and have sensitivity to environmental factors such as temperature, wind speed and supply voltage. There are uncertainties introduced also because of sensor-to-sensor response variability, although this is less well reported. The sensitivity of Metal Oxide Sensors (MOS) to volatile organic compounds (VOCs) changed with relative humidity (RH) by up to a factor of five over the range of 19-90% RH and with an uncertainty in the correction of a factor of two at any given RH. The short-term (second to minute) stabilities of MOS and electrochemical CO sensor responses were reasonable. During more extended use, inter-sensor quantitative comparability was degraded due to unpredictable variability in individual sensor responses (to either measurand or interference or both) drifting over timescales of several hours to days. For timescales longer than a week identical sensors showed slow, often downwards, drifts in their responses which diverged across six CO sensors by up to 30% after two weeks. The measurement derived from the median sensor within clusters of 6, 8 and up to 21 sensors was evaluated against individual sensor performance and external reference values. The clustered approach maintained the cost competitiveness of a sensor device, but the median concentration from the ensemble of sensor signals largely eliminated the randomised hour-to-day response drift seen in individual sensors and excluded the effects of small numbers of poorly performing sensors that drifted significantly over longer time periods. The results demonstrate that for individual sensors to be optimally comparable to one another, and to reference instruments, they would likely require frequent calibration. The use of a cluster median value eliminates unpredictable medium term response changes, and other longer term outlier behaviours, extending the likely period needed between calibration and making a linear interpolation between calibrations more appropriate. Through the use of sensor clusters rather than individual sensors, existing low cost technologies could deliver significantly improved quality of observations.

10.
Somatosens Mot Res ; 34(1): 58-64, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28270049

RESUMO

Barrels XXIX brought together researchers focusing on the rodent barrel cortex and associated systems. The meeting revolved around three themes: thalamocortical interactions in motor control, touch in rodent, monkey, and humans, and the nature of the multisensory computations the brain makes. Over two days these topics were covered as well as many more presentations that focused on the physiology, behavior, and development of the rodent whisker-to-barrel cortex system.


Assuntos
Córtex Somatossensorial/fisiologia , Tato , Vibrissas/fisiologia , Vias Aferentes/fisiologia , Animais , Humanos
11.
Eur J Neurosci ; 44(1): 1779-86, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27152754

RESUMO

Diabetic neuropathy is a common, and often debilitating, secondary complication of diabetes mellitus. As pain, hypersensitivity and paraesthesias present in a distal-proximal distribution, symptoms are generally believed to originate from damaged afferents within the peripheral nervous system. Increasing evidence suggests altered processing within the central nervous system in diabetic neuropathy contributes towards somatosensory dysfunction, but whether the accurate coding and relay of peripherally encoded information through the central nervous system is altered in diabetes is not understood. Here, we applied the strengths of the rodent whisker-barrel system to study primary afferent-thalamic processing in diabetic neuropathy. We found that neurons in the thalamic ventral posteromedial nucleus from rats with experimental diabetic neuropathy showed increased firing to precisely graded, multidirectional whisker deflection compared to non-diabetic rats. This thalamic hyperactivity occurred without any overt primary afferent dysfunction, as recordings from the trigeminal ganglion showed these primary afferents to be unaffected by diabetes. These findings suggest that central amplification can substantially transform ascending sensory input in diabetes, even in the absence of a barrage of ectopic primary afferent activity.


Assuntos
Potenciais de Ação , Diabetes Mellitus Experimental/fisiopatologia , Neuropatias Diabéticas/fisiopatologia , Núcleos Talâmicos/fisiopatologia , Animais , Masculino , Neurônios Aferentes/fisiologia , Ratos , Ratos Sprague-Dawley , Núcleos Talâmicos/citologia , Vibrissas/inervação , Vibrissas/fisiologia
12.
Faraday Discuss ; 189: 105-20, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-27092375

RESUMO

There is growing global consumption of non-fossil fuels such as ethanol made from renewable biomass. Previous studies have shown that one of the main air quality disadvantages of using ethanol blended fuels is a significant increase in the production of acetaldehyde, an unregulated and toxic pollutant. Most studies on the impacts of ethanol blended gasoline have been carried out in the US and Brazil, with much less focus on the UK and Europe. We report time resolved measurements of ethanol in London during the winter and summer of 2012. In both seasons the mean mixing ratio of ethanol was around 5 ppb, with maximum values over 30 ppb, making ethanol currently the most abundant VOC in London air. We identify a road transport related source, with 'rush-hour' peaks observed. Ethanol is strongly correlated with other road transport-related emissions, such as small aromatics and light alkanes, and has no relationship to summer biogenic emissions. To determine the impact of road transport-related ethanol emission on secondary species (i.e. acetaldehyde and ozone), we use both a chemically detailed box model (incorporating the Master Chemical Mechanism, MCM) and a global and nested regional scale chemical transport model (GEOS-Chem), on various processing time scales. Using the MCM model, only 16% of the modelled acetaldehyde was formed from ethanol oxidation. However, the model significantly underpredicts the total levels of acetaldehyde, indicating a missing primary emission source, that appears to be traffic-related. Further support for a primary emission source comes from the regional scale model simulations, where the observed concentrations of ethanol and acetaldehyde can only be reconciled with the inclusion of large primary emissions. Although only constrained by one set of observations, the regional modelling suggests a European ethanol source similar in magnitude to that of ethane (∼60 Gg per year) and greater than that of acetaldehyde (∼10 Gg per year). The increased concentrations of ethanol and acetaldehyde from primary emissions impacts both radical and NOx cycling over Europe, resulting in significant regional impacts on NOy speciation and O3 concentrations, with potential changes to human exposure to air pollutants.


Assuntos
Poluição do Ar/análise , Etanol/análise , Acetaldeído/análise , Cromatografia Gasosa , Etanol/química , Modelos Lineares , Londres , Óxidos de Nitrogênio/análise , Oxirredução , Ozônio/análise , Estações do Ano
13.
Elife ; 52016 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-26880559

RESUMO

Primary sensory neurons form the interface between world and brain. Their function is well-understood during passive stimulation but, under natural behaving conditions, sense organs are under active, motor control. In an attempt to predict primary neuron firing under natural conditions of sensorimotor integration, we recorded from primary mechanosensory neurons of awake, head-fixed mice as they explored a pole with their whiskers, and simultaneously measured both whisker motion and forces with high-speed videography. Using Generalised Linear Models, we found that primary neuron responses were poorly predicted by whisker angle, but well-predicted by rotational forces acting on the whisker: both during touch and free-air whisker motion. These results are in apparent contrast to previous studies of passive stimulation, but could be reconciled by differences in the kinematics-force relationship between active and passive conditions. Thus, simple statistical models can predict rich neural activity elicited by natural, exploratory behaviour involving active movement of sense organs.


Assuntos
Neurônios/fisiologia , Córtex Somatossensorial/fisiologia , Percepção do Tato , Potenciais de Ação , Animais , Locomoção , Camundongos , Modelos Neurológicos , Modelos Estatísticos , Vibrissas/fisiologia
14.
Nat Commun ; 7: 10267, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26758808

RESUMO

Air parcels with mixing ratios of high O3 and low H2O (HOLW) are common features in the tropical western Pacific (TWP) mid-troposphere (300-700 hPa). Here, using data collected during aircraft sampling of the TWP in winter 2014, we find strong, positive correlations of O3 with multiple biomass burning tracers in these HOLW structures. Ozone levels in these structures are about a factor of three larger than background. Models, satellite data and aircraft observations are used to show fires in tropical Africa and Southeast Asia are the dominant source of high O3 and that low H2O results from large-scale descent within the tropical troposphere. Previous explanations that attribute HOLW structures to transport from the stratosphere or mid-latitude troposphere are inconsistent with our observations. This study suggest a larger role for biomass burning in the radiative forcing of climate in the remote TWP than is commonly appreciated.

15.
Proc Natl Acad Sci U S A ; 112(30): 9281-6, 2015 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-26124148

RESUMO

Halogens in the troposphere are increasingly recognized as playing an important role for atmospheric chemistry, and possibly climate. Bromine and iodine react catalytically to destroy ozone (O3), oxidize mercury, and modify oxidative capacity that is relevant for the lifetime of greenhouse gases. Most of the tropospheric O3 and methane (CH4) loss occurs at tropical latitudes. Here we report simultaneous measurements of vertical profiles of bromine oxide (BrO) and iodine oxide (IO) in the tropical and subtropical free troposphere (10 °N to 40 °S), and show that these halogens are responsible for 34% of the column-integrated loss of tropospheric O3. The observed BrO concentrations increase strongly with altitude (∼ 3.4 pptv at 13.5 km), and are 2-4 times higher than predicted in the tropical free troposphere. BrO resembles model predictions more closely in stratospheric air. The largest model low bias is observed in the lower tropical transition layer (TTL) over the tropical eastern Pacific Ocean, and may reflect a missing inorganic bromine source supplying an additional 2.5-6.4 pptv total inorganic bromine (Bry), or model overestimated Bry wet scavenging. Our results highlight the importance of heterogeneous chemistry on ice clouds, and imply an additional Bry source from the debromination of sea salt residue in the lower TTL. The observed levels of bromine oxidize mercury up to 3.5 times faster than models predict, possibly increasing mercury deposition to the ocean. The halogen-catalyzed loss of tropospheric O3 needs to be considered when estimating past and future ozone radiative effects.

16.
Shoulder Elbow ; 6(1): 23-8, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27582905

RESUMO

BACKGROUND: To evaluate the clinical and radiological outcomes of the modified Latarjet procedure for traumatic, antero-inferior glenohumeral joint instability. METHODS: Case series were used with a mean follow-up of 21.3 months for clinical and radiological review and 47.2 months for recurrent instability. Shoulder function was evaluated by clinical examination and validated shoulder scales: Western Ontario Shoulder Stability Index (WOSI), Melbourne Instability Shoulder Score (MISS) and l'Insalata Shoulder Questionnaire. Shoulder structure was evaluated by computed tomography. RESULTS: Thirty-two cases were enrolled (mean age 27.0 years). One patient reported a redislocation during the follow-up period. Clinical examination revealed that the median external rotation (at 0° and 90° abduction) was reduced on the operative side by 7.5° (p < 0.01) and 10° (p < 0.001), respectively. Subjective shoulder function was good. Mean (SD) scores on the WOSI, MISS and l'Insalata scales were 78.0 (19.7), 75.8 (11.5) and 89.3 (9.9), respectively. No loss of subscapularis strength was identified (p > 0.05). Radiological evaluation revealed a mean (SD) pre-operative glenoid surface area loss of 169.5 (48.5) mm(2) reconstituted surgically by a bone block of 225.4 (73.8) mm(2). Subscapularis muscle bulk was reduced on the operative side, above the level of the muscle split (p < 0.05). CONCLUSIONS: The Latarjet procedure reliably restores lost glenoid surface area, shoulder stability, strength and function. A small loss of external rotation is expected and related to altered subscapularis anatomy.

17.
J R Soc Interface ; 9(72): 1517-28, 2012 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-22279155

RESUMO

Texture perception is studied here in a physical model of the rat whisker system consisting of a robot equipped with a biomimetic vibrissal sensor. Investigations of whisker motion in rodents have led to several explanations for texture discrimination, such as resonance or stick-slips. Meanwhile, electrophysiological studies of decision-making in monkeys have suggested a neural mechanism of evidence accumulation to threshold for competing percepts, described by a probabilistic model of Bayesian sequential analysis. For our robot whisker data, we find that variable reaction-time decision-making with sequential analysis performs better than the fixed response-time maximum-likelihood estimation. These probabilistic classifiers also use whatever available features of the whisker signals aid the discrimination, giving improved performance over a single-feature strategy, such as matching the peak power spectra of whisker vibrations. These results cast new light on how the various proposals for texture discrimination in rodents depend on the whisker contact mechanics and suggest the possibility of a common account of decision-making across mammalian species.


Assuntos
Tomada de Decisões , Modelos Biológicos , Reconhecimento Fisiológico de Modelo , Robótica/métodos , Vibrissas , Animais , Ratos , Robótica/instrumentação , Propriedades de Superfície
18.
Front Neurorobot ; 6: 12, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23293601

RESUMO

Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterized, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability.

19.
Nature ; 453(7199): 1232-5, 2008 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-18580948

RESUMO

Increasing tropospheric ozone levels over the past 150 years have led to a significant climate perturbation; the prediction of future trends in tropospheric ozone will require a full understanding of both its precursor emissions and its destruction processes. A large proportion of tropospheric ozone loss occurs in the tropical marine boundary layer and is thought to be driven primarily by high ozone photolysis rates in the presence of high concentrations of water vapour. A further reduction in the tropospheric ozone burden through bromine and iodine emitted from open-ocean marine sources has been postulated by numerical models, but thus far has not been verified by observations. Here we report eight months of spectroscopic measurements at the Cape Verde Observatory indicative of the ubiquitous daytime presence of bromine monoxide and iodine monoxide in the tropical marine boundary layer. A year-round data set of co-located in situ surface trace gas measurements made in conjunction with low-level aircraft observations shows that the mean daily observed ozone loss is approximately 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. We perform box model calculations that indicate that the observed halogen concentrations induce the extra ozone loss required for the models to match observations. Our results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.


Assuntos
Atmosfera/química , Halogênios/química , Ozônio/química , Água do Mar/química , Clima Tropical , África Ocidental , Oceano Atlântico , Eucariotos/metabolismo , Geografia , Biologia Marinha , Metano/química , Ozônio/análise , Ozônio/efeitos da radiação , Estações do Ano , Água do Mar/microbiologia , Temperatura
20.
Faraday Discuss ; 130: 425-36; discussion 491-517, 519-24, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16161796

RESUMO

A combination of in situ, ground-based observations of marine boundary layer OH concentrations performed by laser-induced fluorescence at Mace Head, Ireland and Cape Grim, Tasmania, and a global chemistry-transport model (GEOS-CHEM) are used to obtain an estimate of the mean concentration of OH in the global troposphere. The model OH field is constrained to the geographically sparse, observed OH concentration averaged over the duration of the measurement campaigns to remove diurnal and synoptic variability. The mean northern and southern hemispheric OH concentrations obtained are 0.91 x 10(6) cm(-3) and 1.03 x 10(6) cm(-3) respectively, consistent with values determined from methyl chloroform observations. The observational OH dataset is heavily biased towards mid-latitude summer and autumn observations in the northern hemisphere, while the global oxidising capacity is dominated by the tropics which is observed extremely sparsely; the implications of these geographical distributions are discussed.

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