Responses of nervous elements of the visual cortex of the chipmunk Eutamias sibiricus to moving and stationary stimuli]

The receptive field organization of cortical units has been studied in experiments with testing by moving and stationary light spots. The size of the receptive fields varied from 3 degrees to 10 degrees. Receptive fields which were tested by a stationary light spot exhibited various types of organization. Some of the neurons produced extensive excitatory on- and off-responses to stimulation by a light spot. Neuronal excitation evoked by light decreased if the stimulus was near the field boundary. Some of the neurons produced either on- or off-responses in any point of the receptive field. A small part of neurons had receptive fields with on- and off-reactions in the center, and either on- or off-responses at the peripheral zones. Most of the neurons exhibited specialization with respect to high-speed motion.     

The “lunching” effect: Pigeons track motion towards food more than motion away from it

Four experiments measured pigeons’ pecking at a small touch-screen image (the CS) that moved towards or away from a source of food (the US). The image's effectiveness as a CS was dependent on its motion, direction, and distance relative to the US. Pecking to the CS increased with proximity to the US when the CS moved towards the US (Experiment 1). This held true even when a departing CS signalled a US of greater magnitude (Experiment 2). Response rates to stationary stimuli were greater the closer they were to the hopper; but rate was less than when the same spot was part of a motion towards food, and greater than when it was part of a motion away (Experiment 3). The rate of responding in all three cases (motion towards, stationary, motion away) decreased exponentially with distance from the hopper. The distance and motion effects observed under these Pavlovian contingencies were different when pecking to the spot was required for reinforcement (Experiment 4).     

Electrophysiological evidence for interaction between retinula cells in the flesh-fly

Summary In the electrical response of retinula cells to polarized light in the flesh-flyBoettcherisca peregrina, the polarization plane which showed the maximum sensitivity (Pol_max phase) to illumination by a small spot of light just large enough to cover only one retinula cell was found to differ from that with illumination by a larger spot of light which included adjacent cells. There was a difference of about 30°.This difference in Pol_max phase was assumed to indicate the occurrence of interaction between retinula cells even in the fly photoreceptor having rhabdom of the open type. This assumption was confirmed by the following experiments. (1) Under selective adaptation by a large spot of polarized light so as to eliminate the interaction effect, the Pol_max phase was found to be the same as that measured by a small spot even though the measurement had been made using a large spot of light. (2) The responses to polarized light illuminated from along some restricted off-axes showed a 60° shift in the Pol_max phase in comparison to those obtained from along the other axes. (3) The spectral sensitivity curves to illumination from along off-axes were almost all the same and were for the peripheral retinula cells. (4) The receptor potentials were found to increase in amplitude in a certain limited off-axis area that corresponded to the specific off-axis direction of illumination which had resulted in a shift of the Pol_max phase.It is concluded from these results that the peripheral retinula cells in the flesh-fly demonstrate interaction between certain two adjacent retinula cells. This interaction is positive but not a simple algebraic sum of the activity of two cells.This work was partly supported by a grant from the Japan Education MinistryI wish to thank the Department of Biology, Faculty of Sciences, Kyushu University (Prof. H. Morita and Prof. H. Tateda) for the constant supply of flesh-flies.     

Magnetic scanometric DNA microarray detection of methyl tertiary butyl ether degrading bacteria for environmental monitoring

A magnetoresistive biosensing platform based on a single magnetic tunnel junction (MTJ) scanning probe and DNA microarrays labeled with magnetic particles has been developed to provide an inexpensive, sensitive and reliable detection of DNA. The biosensing platform was demonstrated on a DNA microarray assay for quantifying bacteria capable of degrading methyl tertiary butyl ether (MTBE), where concentrations as low as 10 pM were detectable. Synthetic probe bacterial DNA was immobilized on a microarray glass slide surface, hybridized with the 48 base pair long biotinylated target DNA and subsequently incubated with streptavidin-coated 2.8 μm diameter magnetic particles. The biosensing platform then makes use of a micron-sized MTJ sensor that was raster scanned across a 3 mm by 5 mm glass slide area to capture the stray magnetic field from the tagged DNA and extract two dimensional magnetic field images of the microarray. The magnetic field output is then averaged over each 100 μm diameter DNA array spot to extract the magnetic spot intensity, analogous to the fluorescence spot intensity used in conventional optical scanners. The magnetic scanning result is compared with results from a commercial laser scanner and particle coverage optical counting to demonstrate the dynamic range and linear sensitivity of the biosensing platform as a potentially inexpensive, sensitive and portable alternative for DNA microarray detection for field applications.     

Chromatic collinear facilitation, further evidence for chromatic form perception

Collinear facilitation of contrast detection of achromatic stimuli has been studied over the past decade by different groups. We measured collinear facilitation of chromatic contrast detection under equal-luminance (photometric quantity) and under isoluminance (minimum motion technique) conditions, as two different controls. The facilitation was tested for chromatic contrast detection of a foveal Gabor signal flanked by two high chromatic-contrast Gabor signals. The results indicated a significant facilitation in the presence of spatial adjacent collinear chromatic contrast signals, when the flankers were located at a short distance, across all observers for three chromatic channels. The facilitation was compared to a non-collinear flanker configuration. The results indicated no facilitation effect at the opposing phase configuration, at a short flanker distance, whereas a small facilitation was observed with a configuration at a longer flanker distance. The findings suggest that the performance and specificity of chromatic collinear facilitation is not impaired with regard to achromatic mechanisms.     

Contrast sensitivity and the detection of moving patterns and features

Theories based on optimal sampling by the retina have been widely applied to visual ecology at the level of the optics of the eye, supported by visual behaviour. This leads to speculation about the additional processing that must lie in between—in the brain itself. But fewer studies have adopted a quantitative approach to evaluating the detectability of specific features in these neural pathways. We briefly review this approach with a focus on contrast sensitivity of two parallel pathways for motion processing in insects, one used for analysis of wide-field optic flow, the other for detection of small features. We further use a combination of optical modelling of image blur and physiological recording from both photoreceptors and higher-order small target motion detector neurons sensitive to small targets to show that such neurons operate right at the limits imposed by the optics of the eye and the noise level of single photoreceptors. Despite this, and the limitation of only being able to use information from adjacent receptors to detect target motion, they achieve a contrast sensitivity that rivals that of wide-field motion sensitive pathways in either insects or vertebrates—among the highest in absolute terms seen in any animal.     

Fundamental properties of intensity, form, and motion perception in the visual nervous systems of Calliphora phaenicia and Musca domestica

Several classes of interneurons in the optic lobes and brain of the insects, Musca domestica and Calliphora phaenicia, have been studied in detail. Visual stimuli have been categorized on the basis of the properties of intensity, form, and motion. Response characteristics of the classes of neural units are described with respect to these three classes of visual stimuli. While those units that detect motion in select directions have a tonic response, form detection units have a phasic response only. Through correlation of the responses of these classes with visual stimuli, it is shown that these units integrate the responses of other units which have very small visual fields. The small-field units are presumed to integrate the output of a small group of adjacent retinula cells and to respond differentially to intensity, form, and motion. It is shown that the response of both form and motion detection units is independent of the direction of pattern intensity gradation. As a consequence of this independence, it is further shown that failure to detect motion properly must start at a spatial wavelength four times the effective sampling station spacing rather than twice as has been predicted previously.     

Polarization contrast and motion detection

Form and motion perception rely upon the visual system’s capacity to segment the visual scene based upon local differences in luminance or wavelength. It is not clear if polarization contrast is a sufficient basis for motion detection. Here we show that crayfish optomotor responses elicited by the motion of images derived from spatiotemporal variations in e-vector angles are comparable to contrast-elicited responses. Response magnitude increases with the difference in e-vector angles in adjacent segments of the scene and with the degree of polarization but the response is relatively insensitive to the absolute values of e-vector angles that compose the stimulus. The results indicate that polarization contrast can support visual motion detection.     

Development and application of white-noise modeling techniques for studies of insect visual nervous system

The nonlinear system identification technique through white-noise stimulation is extended to multi-input, -output systems with consideration given to applications in the functional study of the nervous system. The applicability of the method is discussed in general and in particular for the motion detection neuronal system of the fly. Two series of experiments are performed; one with moving striped-pattern stimuli and the other with spot stimuli of fluctuating intensity. In both cases nonlinear dynamic models are derived which describe the system with considerable accuracy over the frequency range of 0.2–50 Hz and a dynamic amplitude range of about 40-1. These models are able to predict accurately all the discrete experiments so far performed on this system for which the models are applicable. The differences in dynamic characteristics between the corresponding system of the Musca and Phoenicia families of flies are minor except for a difference in latencies and if the difference in geometry of their faceted eyes is taken into account. The large field response of the motion detection unit is a linear weighted summation of all the smaller field highly nonlinear subsystems of which the large field is comprised.     

Cavity spot of carrots - observations on a commercial crop

A single field of commercially-grown carrots was sampled in September at 16 points for cavity spot incidence. Carrot tops, root core and peel were analysed for N, P, K, Ca and Mg, and soils were analysed for organic C, total N, available P, K, Ca, Mg and Na, pH, conductivity and chloride. The incidence of the disorder varied from 0–96% within a small area of field, thus tending to rule out explanations for cavity spot based entirely on weather, genotype etc. Several types of lesion were recorded in addition to ‘typical’ cavity spot, and their incidence was found to be mutually correlated. Most of these (including splitting) were positively correlated with cavity spot, and tended to be positively related to concentrations of macroelements in the carrot peel (especially N and Ca): however, ‘scabs’ were very strikingly dissociated from cavities (both on a plot and individual root basis). This dissociation appeared to be connected with soil pH, in that scabs were most common above pH 6-5, whereas cavities were most frequent below this pH.     

A LAMP-SNP Assay Detecting C580Y Mutation in Pfkelch13 Gene from Clinically Dried Blood Spot Samples

Artemisinin resistance (ART) has been confirmed in Greater Mekong Sub-region countries. Currently, C580Y mutation on Pfkelch13 gene is known as the molecular marker for the detection of ART. Rapid and accurate detection of ART in field study is essential to guide malaria containment and elimination interventions. A simple method for collection of malaria-infected blood is to spot the blood on filter paper and is fast and easy for transportation and storage in the field study. This study aims to evaluate LAMP-SNP assay for C580Y mutation detection by introducing an extra mismatched nucleotide at the 3’ end of the FIP primer. The LAMP-SNP assay was performed in a water bath held at a temperature of 56°C for 45 min. LAMP-SNP products were interpreted by both gel-electrophoresis and HNB-visualized changes in color. The method was then tested with 120 P. falciparum DNA from dried blood spot samples. In comparing the LAMP-SNP assay results with those from DNA sequencing of the clinical samples, the 2 results fully agreed to detect C580Y. The sensitivity and specificity of the LAMP-SNP assay showed 100%. There were no cross-reactions with other Plasmodium species and other Pfkelch13 mutations. The LAMP-SNP assay performed in this study was rapid, reliable, and useful in detecting artemisinin resistance in the field study.     

Measurements of Euglena motion parameters by laser light scattering.

Measurements of Euglena gracilis motion parameters have been performed by the spectral analysis of the scattered laser light. Samples were oriented by a radiofrequency field to obtain easily interpretable spectra. Cell rotation frequency and flagellar beating frequency distributions were obtained from the homodyne spectra, whereas the Doppler lines obtained at small observation angles by heterodyne detection yielded the swimming speed distributions. We discuss the broadening of the heterodyne spectra at large angles of observation. An application of this method to the study of the photo-kinetic effect is also described.     

Age-Related Changes in Expectation-Based Modulation of Motion Detectability

Expecting motion in some particular direction biases sensitivity to that direction, which speeds detection of motion. However, the neural processes underlying this effect remain underexplored, especially in the context of normal aging. To address this, we examined younger and older adults'' performance in a motion detection task. In separate conditions, the probability was either 50% or 100% that a field of dots would move coherently in the direction a participant expected (either vertically or horizontally). Expectation and aging effects were assessed via response times (RT) to detect motion and electroencephalography (EEG). In both age groups, RTs were fastest when motion was similar to the expected direction of motion. RT tuning curves exhibited a characteristic U-shape such that detection time increased with an increasing deviation from the participant''s expected direction. Strikingly, EEG results showed an analogous, hyperbolic curve for N1 amplitude, reflecting neural biasing. Though the form of behavioral and EEG curves did not vary with age, older adults displayed a clear decline in the speed of detection and a corresponding reduction in EEG N1 amplitude when horizontal (but not vertical) motion was expected. Our results suggest that expectation-based detection ability varies with age and, for older adults, also with axis of motion.     

The effect of a moving foveal target on the subjective sensation of motion

In this paper, we report on two experiments concerning the effect of the visual field of fovea on the subjective estimation of angular velocity. Experiment 1 investigates the effect of a slow moving target on the perception of self motion. The result of this experiment can be summarized as follows: a slow moving target seen in the visual field of fovea by a stationary person generates in this person a sensation of self rotation in the same direction as the motion of the target. This phenomenon will be called foveal induced ego motion. Experiment 2 investigates the latency for the detection of a self angular acceleration when the person focusses his fovea on a slowly moving target. From the results of this experiment we conclude that the latency for detection of a small self angular acceleration is shorter if the person sees a small foveal target moving with respect to the person in the direction of self rotation than if that small foveal target is moving (with respect to the person) in the opposite direction. The results of these experiments help us in refining existing models of visual-vestibular interaction, by providing a model which accounts for the phenomenon of oculogyral illusion.This research was conducted while serving as a Visiting Professor at the Man Vehicle Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA     

A two dimensional field theory for motion computation

The local extraction of motion information from brightness patterns by individual movement detectors of the correlation-type is considered in the first part of the paper. A two-dimensional field theory of movement detection is developed by treating the distance between two adjacent photoreceptors as a differential. In the first approximation of the theory we only consider linear terms of the time interval between the reception of a contrast element and its delayed representation by the detector and linear terms of the spatial distances between adjacent photoreceptors. As a result we may neglect terms of higher order than quadratic in a Taylor series development of the brightness pattern. The responses of pairs of individual movement detectors are combined to a local response vector. In the first approximation of the detector field theory the response vector is proportional to the instantaneous pattern velocity vector and linearly dependent on local properties of the moving pattern. The linear dependence on pattern properties is represented by a two by two tensor consisting of elements which are nonlinear, local functional of the moving pattern. Some of the properties of the tensor elements are treated in detail. So, for instance, it is shown that the off-diagonal elements of the tensor disappear when the moving pattern consists of x- and y-dependent separable components. In the second part of the paper the tensor relation leading to the output of a movement detector pair is spatially integrated. The result of the integration is an approximation to a summation of the outputs of an array of detector pairs. The spatially integrated detector tensor relates the translatory motion vector to the resultant output vector. It is shown that the angle between the motion vector and the resultant output vector is always smaller than ±90° whereas the angle between the motion vector and local response vectors, elicited by detector pairs, may cover the entire angular range. In the discussion of the paper the limits of the field theory for motion computation as well as its higher approximations are pointed out in some detail. In a special chapter the dependence of the detector response on the pattern properties is treated and in another chapter questions connected with the so called aperture problem are discussed. Furthermore, properties for compensation of the pattern dependent deviation angle by spatial physiological integration are mentioned in the discussion.     

Electron microscopic demonstration of lectin binding sites in the taste buds of the European catfish Silurus glanis (Teleostei)

Taste buds in the European catfish Silurus glanis were examined with electron microscopic lectin histochemistry. For detection of carbohydrate residues in sensory cells and adjacent epithelial cells, gold-, ferritin- and biotin-labeled lectins were used. A post-embedding procedure carried out on tissue sections embedded in LR-White was applied to differentiate between the sensory cells: The lectins from Helix pomatia (HPA) and Triticum vulgare (WGA) bound to N-acetyl-galactosamine and to N-acetylglucosamine residues occurring especially in vesicles of dark sensory cells. This indicates a secretory function of these cells. Most light sensory cells--with some exceptions, probably immature cells--, are HPA-negative. The mucus of the receptor field and at the top of the adjacent epithelial cells was strongly HPA-positive. Pre-embedding studies were performed in order to obtain information about the reaction of the mucus with lectins under supravital conditions. The mucus of the taste bud receptor field exhibited intensive binding to WGA, but not to the other lectins tested. Most lectins bound predominantly to the surface mucus of the nonsensory epithelium and to the marginal cells close to the receptor field. The strong lectin binding to mucins and the relatively weak lectin binding to cell surface membranes in pre-embedding studies suggest that the mucus possibly serves as a barrier which is passed selectively only by a small amount of lectins or lectin-carbohydrate complexes. Lectin-carbohydrate interactions may play a role in recognition phenomena on the plasmalemmata of the taste bud sensory cells. Recognition processes directed to bacteria or viruses should be considered as well.     

Rapid Detection of Shrimp White Spot Syndrome Virus by Real Time,Isothermal Recombinase Polymerase Amplification Assay

White spot syndrome virus (WSSV) causes large economic losses to the shrimp aquaculture industry, and thus far there are no efficient therapeutic treatments available against this lethal virus. In this study, we present the development of a novel real time isothermal recombinase polymerase amplification (RPA) assay for WSSV detection on a small ESEQuant Tube Scanner device. The RPA sensitivity, specificity and rapidity were evaluated by using a plasmid standard as well as viral and shrimp genomic DNAs. Compared with qPCR, the RPA assay revealed more satisfactory performance. It reached a detection limit up to 10 molecules in 95% of cases as determined by probit analysis of 8 independent experiments within 6.41±0.17 min at 39°C. Consequently, this rapid RPA method has great application potential for field use or point of care diagnostics.     

A Computer-Controlled Video System for Real-Time Recording of Insect Flight in Three Dimensions

A computer-controlled video system for real-time recording of insect flight in three dimensions is described. The flight paths of moths were recorded in a flight tunnel using two CCD cameras placed adjacent to each other at angles of 45 and 135° to the flight tunnel axis and separated by a distance of 120 cm. They were connected to two 2⁸-level gray-scale frame grabbers via two external synchronizers. The two-dimensional coordinates of the flying insect were obtained from the two cameras at 40-ms intervals and transferred to host computer for processing and monitor for real-time display. Due to speed limitation in the image acquisition hardware, construction of the three-dimensional file was carried off-line. The flying insect was rendered as a dark spot in a bright background using a homogeneous light source. As the insect enters into the field of view of the two cameras, the light distribution changes, and the frame grabber detects only those variation in the light distribution which results from a flying insect. The target insect can be as small as 3 pixels and can be tracked in a stereoscopic field of view 60 cm long and 50 cm high. A method was developed that allowed for scalar scoring of various pheromone sources to assess their attractiveness using vector flight parameters. This method was applied successfully for optimization of pheromone blend of the grapevine moth, Lobesia botrana.     

Reduction of spontaneous somatic mutation frequency by a low-dose X irradiation of Drosophila larvae and possible involvement of DNA single-strand damage repair

The third instar larvae of Drosophila were irradiated with X rays, and the somatic mutation frequency in their wings was measured after their eclosion. In the flies with normal DNA repair and apoptosis functions, 0.2 Gy irradiation at 0.05 Gy/min reduced the frequency of the so-called small spot (mutant cell clone with reduced reproductive activity) compared with that in the sham-irradiated flies. When apoptosis was suppressed using the baculovirus p35 gene, the small spot frequency increased four times in the sham-irradiated control group, but the reduction by the 0.2-Gy irradiation was still evident. In a non-homologous end joining-deficient mutant, the small spot frequency was also reduced by 0.2 Gy radiation. In a mutant deficient in single-strand break repair, no reduction in the small spot frequency by 0.2 Gy radiation was observed, and the small spot frequency increased with the radiation dose. Large spot (mutant cell clone with normal reproductive activity) frequency was not affected by suppression of apoptosis and increased monotonically with radiation dose in wild-type larvae and in mutants for single- or double-strand break repair. It is hypothesized that some of the small spots resulted from single-strand damage and, in wild-type larvae, 0.2 Gy radiation activated the normal single-strand break repair gene, which reduced the background somatic mutation frequency.     

Three theories of stroboscopic motion detection

The three theories derive from three different paradigms. Suprathreshold judgements of perceived quality of motion in multi-flash displays are modelled by space-time Fourier analysis of the motion stimulus. Stroboscopic motion is perceived as being different from real motion to the extent that the additional Fourier components in stroboscopic motion are detectable. Stroboscopic motion of dots along conflicting paths leads to perceptual competition. The theory to describe perceptual I solution derives and proves the uniqueness of strength functions computed only from the time and from the distance between successive points on each path. Time-strength and motion-strength add to determine path-strength; only the strongest path is perceived. Motion-direction detection in continuously drifting two-flash combinations of sinusoidal gratings is described by elaborated Reichardt detectors (ERDs) that compute the covariance of temporal events in two adjacent locations. Other apparently different, detectors that account for direction-detection data are shown to be equivalent to ERDs.