Joint coding of visual input and eye/head position in V1 of freely moving mice

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Active sensing in a freely walking spider: look where to go

The Central American hunting spider Cupiennius salei, like most other spiders, has eight eyes, one pair of principal eyes and three pairs of secondary eyes. The principal eyes and one pair of the secondary eyes have almost completely overlapping visual fields, and presumably differ in function. The retinae of the principal eyes can be moved independently by two pairs of eye muscles each, whereas the secondary eyes do not have such eye muscles. The behavioural relevance of retinal movements of freely moving spiders was investigated by a novel dual-channel telemetric registration of the eye muscle activities. Walking spiders shifted the ipsilateral retina with respect to the walking direction before, during and after a turning movement. The change in the direction of vision in the ipsilateral anterior median eye was highly correlated with the walking direction, regardless of the actual light conditions. The contralateral retina remained in its resting position. This indicates that Cupiennius salei shifts it visual field in the walking direction not only during but sometimes previous to an intended turn, and therefore “peers” actively into the direction it wants to turn.     

Cone visual pigments and retinal mosaics in the striped marlin

Three different cone photoreceptor visual pigments in the retina of striped marlin Tetrapturus audax were found with the aid of microspectrophotometry. This provides the first evidence for the basis of colour vision in the Istiophoridae. Furthermore, regional variations in photoreceptor density, type and spatial arrangement indicate differing visual capabilities along different visual axes.     

Shaping of Receptive Fields in the Visual Cortex During Retinal Maturation

We present a computational study of the formation of simple-cell receptive field patterns in the primary visual cortex. Based on the observation that the spatial frequency of the retinal filter increases postnatally, our results explain differences in the time course of the development of orientation selectivity in binocularly deprived and normally reared kittens. Development after eye-opening in normal animals is modelled by training with natural images, whereas in the case of binocular deprivation noise-like stimulation continues. Further, it is shown that different orientation selectivities are obtained for network models trained with natural images in contrast to random phase images of identical second order statistics. The latter finding suggests that higher-order statistics of the inputs influences development of primary visual cortex. Finally, we search for quantities that identify possible signatures of natural image statistics in order to specify the amount of constructiveness that visual experience has on the formation of receptive fields.     

Saccadic head and thorax movements in freely walking blowflies

Visual information processing is adapted to the statistics of natural visual stimuli, and these statistics depend to a large extent on the movements of an animal itself. To investigate such movements in freely walking blowflies, we measured the orientation and position of their head and thorax, with high spatial and temporal accuracy. Experiments were performed on Calliphora vicina, Lucilia cuprina and L. caesar. We found that thorax and head orientation of walking flies is typically different from the direction of walking, with differences of 45° common. During walking, the head and the thorax turn abruptly, with a frequency of 5–10 Hz and angular velocities in the order of 1,000°/s. These saccades are stereotyped: head and thorax start simultaneously, with the head turning faster, and finishing its turn before the thorax. The changes in position during walking are saccade-like as well, occurring synchronously, but on average slightly after the orientation saccades. Between orientation saccades the angular velocities are low and the head is held more stable than the thorax. We argue that the strategy of turning by saccades improves the performance of the visual system of blowflies.     

Influence of visual targets and landmarks on honey bee foraging and waggle dancing

Animals use diverse sensory stimuli to navigate their environment and to recognize rewarding food sources.Honey bees use visual atributes of the targeted food source,such as its color,shape,size,direction and distance from the hive,and the landmarks around it to navigate during foraging.They transmit the location information of the food source to other bees if it is highly rewarding.To investigate the relative importance of these attributes,we trained bees to feeders in two different experiments.In the first experiment,we asked whether bees prefer to land on(a)a similar feeder at a different distance on the same heading or on(b)a visually distinct feeder located at the exact same location.We found that,within a short foraging range,bees relied heavily on the color and the shape of the food source and to a lesser extent on its distance from the hive.In the second experiment,we asked if moving the main landmark or the feeder(visual target)influenced recruitment dancing for the feeder.We found that foragers took longer to land and danced fewer circuits when the location of the food source,or a major landmark associated with it,changed.These results demonstrate that prominent visual atributes of food sources and landmarks are evidently more reliable than distance information and that foraging bees heavily utilize these visual cues at the later stages of their journey.     

Neural networks with constrained inputs as models for pattern formation in primate visual cortex

We present a neural network model for the formation of ocular dominance stripes on primate visual cortex and examine the generic phase behavior and dynamics of the model. The dynamical equation of ocular dominance development can be identified with a class of Langevin equations with a nonconserved order parameter. We first set up and examine an Ising model with long-range interactions in an external field, which is equivalent to the model described by the Langevin equation. We use both mean-field theory and Monte-Carlo simulations to study the equilibrium phase diagram of this equivalent Ising model. The phase diagram comprises three phases: a striped phase, a hexagonal bubble phase, and a uniform paramagnetic phase. We then examine the dynamics of the striped phase by solving the Langevin equation both numerically and by singular perturbation theory. Finally, we compare the results of the model with physiological data. The typical striped structure of the ocular dominance columns corresponds to the zero-field configurations of the model. Monocular deprivation can be simulated by allowing the system to evolve in the absence of an external field at early times and then continuing the simulation in the presence of an external field. The physical and physiological applications of our model are discussed in the conclusion.     

Periodic inversion of the vertical component of the earth's magnetic field influences fluctuations of visual sensitivity in humans.

According to theoretical considerations, the magnetic field of the earth could influence the first steps of light-induced changes in ocular photopigment, an effect that is thought to underlie the magnetic orientation of some animals. To find out whether man could be influenced in this way, we have tested the effect of an artificial fluctuation in the direction of the earth's magnetic field on oscillations of the visual sensitivity in 27 healthy subjects. The resultant spectra show a significant influence of the field fluctuations, indicating that man is sensitive to changes in the direction of the earth's magnetic field.     

Impaired clustered protocadherin‐α leads to aggregated retinogeniculate terminals and impaired visual acuity in mice

Clustered protocadherins (cPcdhs) comprising cPcdh‐α, ‐β, and ‐γ, encode a large family of cadherin‐like cell‐adhesion molecules specific to neurons. Impairment of cPcdh‐α results in abnormal neuronal projection patterns in specific brain areas. To elucidate the role of cPcdh‐α in retinogeniculate projections, we investigated the morphological patterns of retinogeniculate terminals in the lateral geniculate (LG) nucleus of mice with impaired cPcdh‐α. We found huge aggregated retinogeniculate terminals in the dorsal LG nucleus, whereas no such aggregated terminals derived from the retina were observed in the olivary pretectal nucleus and the ventral LG nucleus. These aggregated terminals appeared between P10 and P14, just before eye opening and at the beginning of the refinement stage of the retinogeniculate projections. Reduced visual acuity was observed in adult mice with impaired cPcdh‐α, whereas the orientation selectivity and direction selectivity of neurons in the primary visual cortex were apparently normal. These findings suggest that cPcdh‐α is required for adequate spacing of retinogeniculate projections, which may be essential for normal development of visual acuity.

     

Fixation and optomotor response of walking colorado beetles: interaction with spontaneous turning tendencies

Abstract The paths of Colorado beetles ( Leptinotarsa decemlineata Say) in a featureless environment are circular, like those of other species studied. The turning velocity may reach 35^o/s and is due to an internal asymmetry, which may change spontaneously. Normally, all control loops of the insect, like fixation or optomotor responses, must work against this asymmetry to stabilize the insect's path. Stationary vertical patterns damp this turning tendency, but their effect is not strong enough to induce a straight path. Only 70% of the turning tendency can be so eliminated. This reaction is termed optomotor response because it can be adequately described with the parameter turning velocity alone. The insect's path was stabilized more effectively when pattern wavelengths were greater than 60^o. The insects seemed to fixate these wider stripes. This reaction is termed fixation because the correlation between pattern components and insect's course becomes prominent.
A comparison was made between these reactions to stationary patterns and to turning patterns. No differences could be found in the behavioural reactions to the different situations. This suggests that the insect does not use an internal representation of its spontaneous turning tendency to discriminate between the type of turning of the optical environment. These results can be explained by a simple feedback control loop with an additive interaction between the internal turning command and feedback signals from the eyes.     

Convergence of visual,haltere, and prosternai inputs at neck motor neurons of Calliphora erythrocephala

Summary Neck muscles of Calliphora erythrocephala, situated in the anterior prothorax, are innervated on each side by 8 motor neurons arising in the brain (cervical nerve neurons, CN1–8) and at least 13 motor neurons arising in the prothoracic ganglion (anterior dorsal and frontal nerve neurons, ADN1,2 and FN1-11). Three prominent motor neurons (CN6 and FN1,2) are described in detail with special emphasis on their relationships with giant visual interneurons from the lobula plate, haltere interneurons, and primary afferents from the prosternal organs and halteres. These sensory organs detect head movement and body yaw, respectively. Neuronal relationships indicate that head movement is under multimodal sensory control that includes giant motion-sensitive neurons previously supposed to mediate the optomotor response in flying flies. The described pathways provide anatomical substrates for the control of optokinetic and yaw-incurred head movements that behavioural studies have shown must exist.     

Retinal nerve fiber layer birefringence evaluated with polarization sensitive spectral domain OCT and scanning laser polarimetry: A comparison

A polarization‐sensitive spectral domain optical coherence tomography (PS‐SD‐OCT) system is used to measure phase retardation and birefringence of the human retinal nerve fiber layer (RNFL) in vivo. The instrument records three parameters simultaneously: intensity, phase retardation and optic‐axis orientation. 3D data sets are recorded in the optic nerve‐head area of a healthy and a glaucomatous eye, and the results are presented in various ways: En‐face phase‐retardation maps of the RNFL are generated from the recorded 3D data and results are compared with scanning laser polarimetry (SLP). The depth information provided by OCT is used to segment the RNFL in the intensity image and measure the RNFL thickness. From the retardation and thickness data, 2D birefringence maps of the RNFL are derived. Circumpapillary plots of RNFL retardation and thickness obtained by PS‐SD‐OCT are quantitatively compared with those obtained by SLP. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

初级视觉皮层“简单”与“复杂”神经元动力学的计算建模

本文回顾了我们在哺乳动物视觉皮层的建模工作.利用初级视觉皮层的大规模神经元网络模型,我们解释了初级视觉皮层里“简单”与“复杂”神经元现象的网络机制.所谓的“简单”细胞对视觉刺激的反应近似线性,而“复杂”细胞对视觉刺激是非线性的.我们的模型成功地再现了简单和复杂细胞分布的实验数据.     

Correspondences in visual imaging and spatial orientation in dreaming and film viewing.

New directions in film and media theory have begun to focus on precognitive, embodied aspects of film viewing. Drawing on these recent theoretical approaches, this article examines correspondences between the brain–mind state of the dreamer and the film viewer and formal similarities between the cinematic image and dream images. First, the study asks whether cinema's evolution toward the production of images that are more easily processed by the brain has also made film images easily accessible during dream-sleep. Then it shows how the cinematic image and the visual imaging of dreams depend on a similar construction of navigable space. The analysis suggests that the bodily systems for simulating movement and establishing spatial orientation function in a similar manner during dreaming and film viewing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

States of high conductance in a large-scale model of the visual cortex

This paper reports on the consequences of large, activity dependent, synaptic conductances for neurons in a large-scale neuronal network model of the input layer 4C of the Macaque primary visual cortex (Area V1). This high conductance state accounts for experimental observations about orientation selectivity, dynamics, and response magnitude (D. McLaughlin et al. (2000) Proc. Natl. Acad. Sci. USA 97: 8087–8092), and the linear dependence of Simple cells on visual stimuli (J. Wielaard et al. (2001) J. Neuroscience 21: 5203–5211). The source of large conductances in the model can be traced to inhibitory corticocortical synapses, and the model's predictions of large conductance changes are consistent with recent intracellular measurements (L. Borg-Graham et al. (1998) Nature 393: 369–373; J. Hirsch et al. (1998) J. Neuroscience 15: 9517–9528; J.S. Anderson et al. (2000) J. Neurophysiol. 84: 909–926). During visual stimulation, these conductances are large enough that their associated time-scales become the shortest in the model cortex, even below that of synaptic interactions. One consequence of this activity driven separation of time-scales is that a neuron responds very quickly to temporal changes in its synaptic drive, with its intracellular membrane potential tracking closely an effective reversal potential composed of the instantaneous synaptic inputs. From the effective potential and large synaptic conductance, the spiking activity of a cell can be expressed in an interesting and simplified manner, with the result suggesting how accurate and smoothly graded responses are achieved in the model network. Further, since neurons in this high-conductance state respond quickly, they are also good candidates as coincidence detectors and burst transmitters.