How the two eyes add together: monocular properties of the visually guided orientation behaviour of flies

In this account fixation and the torque response to a transient moving stripe of flying femaleMusca domestica with monocular sight was tested. This was made by either covering one eye of the fly with opaque paint or by placing a screen in front of one side of the fly's visual field. A stripe was moved with constant speed once around the fly clockwise and, after a pause, counterclockwise. The torque response of the fly was measured during the motion of the stripe and shortly beforehand. The results demonstrated that the monocular torque response to progressive (from front to back) motion and regressive (from back to front) motion essentially do not differ from the binocular response, except for the region of bionocular overlap. The beginning of the response of a fly with monocular vision to progressive motion is 11 ° (on average) before the direction of flight (0°), which means that the maximal functional binocular overlap of femaleMusca domestica is stretched at least 15° to each side (3.1). In addition, the shape of the monocular torque response to a progressively moving stripe was determined (see Figs. 5Ia and 5IIb). In other experiments similar to the ones described above, a screen was placed on one side of the fly's visual field or then on the other, (instead of covering one eye) and the torque response to the moving stripe was measured. Using this method, a delay response of 90 ms was measured. We suggest that this is the delay of the direction-sensitive component of the torque response, and therefore an additional argument for the existence of two components for the optomotor torque response. Flies with a covered eye or with a screen placed in front of one side of the visual field were able to fixate a single narrow long black stripe. This, however, was possible only when an additional offset signal was added, in order to give the stripe a constant velocity component. As a result there was a shift of the fixation towards the unobscured eye. The shift was small for the monocular flies, and it was larger (13° on average) when the screen was on one side of the fly. A new type of laser torquethrust transducer was developed and is described.     

A computational model of visually guided locomotion in lamprey

This study addresses mechanisms for the generation and selection of visual behaviors in anamniotes. To demonstrate the function of these mechanisms, we have constructed an experimental platform where a simulated animal swims around in a virtual environment containing visually detectable objects. The simulated animal moves as a result of simulated mechanical forces between the water and its body. The undulations of the body are generated by contraction of simulated muscles attached to realistic body components. Muscles are driven by simulated motoneurons within networks of central pattern generators. Reticulospinal neurons, which drive the spinal pattern generators, are in turn driven directly and indirectly by visuomotor centers in the brainstem. The neural networks representing visuomotor centers receive sensory input from a simplified retina. The model also includes major components of the basal ganglia, as these are hypothesized to be key components in behavior selection. We have hypothesized that sensorimotor transformation in tectum and pretectum transforms the place-coded retinal information into rate-coded turning commands in the reticulospinal neurons via a recruitment network mimicking the layered structure of tectal areas. Via engagement of the basal ganglia, the system proves to be capable of selecting among several possible responses, even if exposed to conflicting stimuli. The anatomically based structure of the control system makes it possible to disconnect different neural components, yielding concrete predictions of how animals with corresponding lesions would behave. The model confirms that the neural networks identified in the lamprey are capable of responding appropriately to simple, multiple, and conflicting stimuli.     

The evolution of eyes and visually guided behaviour

The morphology and molecular mechanisms of animal photoreceptor cells and eyes reveal a complex pattern of duplications and co-option of genetic modules, leading to a number of different light-sensitive systems that share many components, in which clear-cut homologies are rare. On the basis of molecular and morphological findings, I discuss the functional requirements for vision and how these have constrained the evolution of eyes. The fact that natural selection on eyes acts through the consequences of visually guided behaviour leads to a concept of task-punctuated evolution, where sensory systems evolve by a sequential acquisition of sensory tasks. I identify four key innovations that, one after the other, paved the way for the evolution of efficient eyes. These innovations are (i) efficient photopigments, (ii) directionality through screening pigment, (iii) photoreceptor membrane folding, and (iv) focusing optics. A corresponding evolutionary sequence is suggested, starting at non-directional monitoring of ambient luminance and leading to comparisons of luminances within a scene, first by a scanning mode and later by parallel spatial channels in imaging eyes.     

Spatial coding of visually guided arm movements in primate motor cortex

Previous studies of the motor cortex in behaving animals were focused on the relations between the activity of single cells, usually pyramidal tract neurons, and parameters of isometric contraction (e.g., intensity of force) or parameters of movement along one axis (e.g., flexion-extension) of a single joint (e.g., elbow or wrist). However, the commonly meaningful behavioral parameter is the trajectory of the hand in extrapersonal space, which is realized by simultaneous motions about two or three joints (e.g., elbow, shoulder, wrist) and concurrent engagement of several muscles. The spatial parameters of a straight trajectory are its direction and extent. We hypothesized that a major function of the motor cortex, among other possible roles, is the specification and control of the direction of the movement trajectory in space. This reference of motor cortical function to the control of spatial aspects of the trajectory differentiated our approach from the other approaches outlined above. We investigated the directional selectivity cells in the arm area of the motor cortex by recording their activity while monkeys moved their hands in various directions in space towards visual targets. There were two salient findings of these studies. First, the intensity of the discharge of single cells varies in an orderly fashion with the direction of movement in space, so that the discharge rate is highest with movements in a preferred direction, and decreases progressively with movements made in directions more and more away from the preferred one. Thus single cells are broadly tuned around a preferred direction which differs among different cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dynamic properties of cardiovascular systems.

A recently derived mathematical model of an isolated heart is extended here to a closed-loop cardiovascular system. Taking the end-diastolic volume as state variable, the authors show that the closed-loop cardiovascular system can be described by a one-dimensional nonlinear discrete dynamical system that depends on parameters describing the systolic and diastolic properties of the heart, heart rate, total peripheral resistance, and arterial capacitance. Studies of this model show that the system possesses a rich spectrum of dynamical behavior, from stable points through stable cycles to a "chaotic" behavior. It is shown that such an analysis of dynamic behavior yields those domains in the parameter space that correspond to a normal and abnormal beating heart, when the heart ejects time-invariant and time-variant (periodic or aperiodic) stable stroke volumes, respectively. Determination of such domains may lead to better understanding of the specific pathologic mechanism involved in the evolution of an abnormal beating heart.     

Rapid steroid influences on visually guided sexual behavior in male goldfish

The ability of steroid hormones to rapidly influence cell physiology through nongenomic mechanisms raises the possibility that these molecules may play a role in the dynamic regulation of social behavior, particularly in species in which social stimuli can rapidly influence circulating steroid levels. We therefore tested if testosterone (T), which increases in male goldfish in response to sexual stimuli, can rapidly influence approach responses towards females. Injections of T stimulated approach responses towards the visual cues of females 30–45 min after the injection but did not stimulate approach responses towards stimulus males or affect general activity, indicating that the effect is stimulus-specific and not a secondary consequence of increased arousal. Estradiol produced the same effect 30–45 min and even 10–25 min after administration, and treatment with the aromatase inhibitor fadrozole blocked exogenous T's behavioral effect, indicating that T's rapid stimulation of visual approach responses depends on aromatization. We suggest that T surges induced by sexual stimuli, including preovulatory pheromones, rapidly prime males to mate by increasing sensitivity within visual pathways that guide approach responses towards females and/or by increasing the motivation to approach potential mates through actions within traditional limbic circuits.     

Rapid steroid influences on visually guided sexual behavior in male goldfish

The ability of steroid hormones to rapidly influence cell physiology through nongenomic mechanisms raises the possibility that these molecules may play a role in the dynamic regulation of social behavior, particularly in species in which social stimuli can rapidly influence circulating steroid levels. We therefore tested if testosterone (T), which increases in male goldfish in response to sexual stimuli, can rapidly influence approach responses towards females. Injections of T stimulated approach responses towards the visual cues of females 30–45 min after the injection but did not stimulate approach responses towards stimulus males or affect general activity, indicating that the effect is stimulus-specific and not a secondary consequence of increased arousal. Estradiol produced the same effect 30–45 min and even 10–25 min after administration, and treatment with the aromatase inhibitor fadrozole blocked exogenous T's behavioral effect, indicating that T's rapid stimulation of visual approach responses depends on aromatization. We suggest that T surges induced by sexual stimuli, including preovulatory pheromones, rapidly prime males to mate by increasing sensitivity within visual pathways that guide approach responses towards females and/or by increasing the motivation to approach potential mates through actions within traditional limbic circuits.     

Calibration plot for proteomics: A graphical tool to visually check the assumptions underlying FDR control in quantitative experiments

In MS‐based quantitative proteomics, the FDR control (i.e. the limitation of the number of proteins that are wrongly claimed as differentially abundant between several conditions) is a major postanalysis step. It is classically achieved thanks to a specific statistical procedure that computes the adjusted p‐values of the putative differentially abundant proteins. Unfortunately, such adjustment is conservative only if the p‐values are well‐calibrated; the false discovery control being spuriously underestimated otherwise. However, well‐calibration is a property that can be violated in some practical cases. To overcome this limitation, we propose a graphical method to straightforwardly and visually assess the p‐value well‐calibration, as well as the R codes to embed it in any pipeline. All MS data have been deposited in the ProteomeXchange with identifier PXD002370 ( http://proteomecentral.proteomexchange.org/dataset/PXD002370 ).     

Mantisbot is a robotic model of visually guided motion in the praying mantis

Insects use highly distributed nervous systems to process exteroception from head sensors, compare that information with state-based goals, and direct posture or locomotion toward those goals. To study how descending commands from brain centers produce coordinated, goal-directed motion in distributed nervous systems, we have constructed a conductance-based neural system for our robot MantisBot, a 29 degree-of-freedom, 13.3:1 scale praying mantis robot. Using the literature on mantis prey tracking and insect locomotion, we designed a hierarchical, distributed neural controller that establishes the goal, coordinates different joints, and executes prey-tracking motion. In our controller, brain networks perceive the location of prey and predict its future location, store this location in memory, and formulate descending commands for ballistic saccades like those seen in the animal. The descending commands are simple, indicating only 1) whether the robot should walk or stand still, and 2) the intended direction of motion. Each joint's controller uses the descending commands differently to alter sensory-motor interactions, changing the sensory pathways that coordinate the joints' central pattern generators into one cohesive motion. Experiments with one leg of MantisBot show that visual input produces simple descending commands that alter walking kinematics, change the walking direction in a predictable manner, enact reflex reversals when necessary, and can control both static posture and locomotion with the same network.     

Dynamic properties of in vitro enzyme systems containing phosphofructokinase.

The dynamic properties of a series of in vitro reaction systems with increasing complexity and containing phosphofructokinase as central enzyme have been investigated. An experimental strategy and a principal mathematical treatment was elaborated to search for the minimum requirements with respect to the enzyme composition of a reaction system for generating limit cycle behaviour. As a criterion, such models have been developed which permit experimental realization by application of a specially designed flow-through equipment. In addition to phosphofructokinase, the following enzymes have been stepwise included into the reaction systems composing the Models 1 through 6: pyruvate kinase, adenylate kinase, hexokinase, and glucose 6-phosphate isomerase. It turned out that only a minimum dynamic system containing phosphofructokinase and pyruvate kinase as well as excesses of adenylate kinase and glucose 6-phosphate isomerase for maintaining equilibrium conditions between the respective reacting species, acquires the property of limit cycle behaviour and, hence, to generate sustained self-oscillations. The approach permits to compute the region of the experimentally variable parameters (influx rates of fructose 6-phosphate and ATP, maximum rate of pyruvate kianse) for which self-oscillatory behaviour can be predicted.     

Contribution of non-sensory neurons in visual cortical areas to visually guided decisions in the rat

1. Download : Download high-res image (124KB)
2. Download : Download full-size image

     

Age dynamics of visually guided behavior and visual evoked potentials of altricial nestlings

Comparative study has been carried out of factors of organization of visually guided feeding behaviour (observation method) and the degree of maturity of the visual mechanisms by the criterion of Wulst EPs formation and of their recovery cycles in normally developing and visually deprived nestlings. In has been established that during the period following the opening of the eyes (5-9th day) the feeding behaviour is connected with diffuse photo-sensitivity of visual mechanisms. Diffuse photo-sensitivity fully provides for natural feeding behaviour at the corresponding stage of development of visual functions. Complete visual deprivation during the whole period of diffuse photo-sensitivity does not influence subsequent development of the visual system.     

Effect of dopamine deficiency on the preparation of visually guided saccadic eye movements

Parameters of saccadic eye movements were studied in patients with Parkinson's disease and control subjects. In parkinsonian patients, the number of slow regular saccades was shown to be increased, and the number of express saccades was shown to be decreased. As a result the mean of saccade latency in patients was longer than in the control group. Moreover, the percentage of multistep saccades in patients with Parkinson's disease. In this case, not one but two or three saccades were performed with smaller amplitude to the target. We point, that the multistep saccades occurred mainly among the express saccades. Obviously, the dopamine deficiency distinguishing parkinsonian patients takes the primary part in the development of saccadic disorders. Degeneration of the nigrostriatal dopamine pathway results in imbalance in activity of the direct and indirect output pathways of the striatum. We suppose that this leads to inhibition of neurons activity in the superior colliculus during the saccade performance, which results in the early saccade interruption. In support of this reasoning, the mean of saccade latency and the percentage of the multistep saccades decreased in patients with Parkinson's disease after dopamine D2/D3 agonist (piribedil) treatment, due to activity restoration of the indirect pathway.     

Post-developmental plasticity of the primary rod pathway allows restoration of visually guided behaviors

1. Download : Download high-res image (181KB)
2. Download : Download full-size image

     

Development of a visually guided Raman spectroscopy probe for cervical assessment during pregnancy

Preterm birth (PTB) is the leading cause of neonatal death, however, accurate prediction methods do not exist. Detection of early changes in the cervix, an organ that biochemically remodels to deliver the fetus, has potential to predict PTB risk. Researchers have employed light‐based methods to monitor biochemical changes in the cervix during pregnancy, however, these approaches required patients to undergo a speculum examination which many patients find uncomfortable and is not standard practice during prenatal care. Herein, a visually guided optical probe is presented that measures the cervix via introduction by bimanual examination, a procedure that is commonly performed during prenatal visits and labor for tactile monitoring of the cervix. The device incorporates a Raman spectroscopy probe for biochemical monitoring and a camera for visualizing measurement location to ensure it is void of cervical mucus and blood. This probe was tested in 15 patients receiving obstetric and gynecological care, and results acquired with and without a speculum revealed similar spectra, demonstrating that the visually guided probe conserved data quality. Additionally, the majority of patients reported reduced discomfort from the device. In summary, the visual guidance probe successfully measured the cervix while integrating with standard prenatal care, reducing a barrier in clinical translation.      

Eye-hand-coordination: A model for computing reaction times in a visually guided reach task

A model is described which provides a simple algorithm to compute the reaction times of saccadic eye movements and reach movements aimed at a single visual target. It is assumed, that the two movements are prepared inparallel and initiated independently unless the preparation of the saccade for some reason takes longer than the preparation of the reach movement. In the latter case the final command to execute the reach movement is synchronized with that to execute the eye movement and therefore the corresponding reaction times are highly correlated in a one-to-one relationship. Random variables are used to predict sets of data that are directly comparable with the experimental results. The algorithm includes the effects of daily practice (learning). The structure of the model and its computational results will be compared with the physiological data from monkey and man.