Multidimensional mapping of visual space with real and simulated stars

A convergent series of studies in monkeys and man suggests that the computation of visual space is performed in several brain regions for different behavioural purposes. Among these multiple spatial areas, the ventral intraparietal cortex, the putamen and the ventral aspect of the premotor cortex (area 6) contain a system for representing visual space near the face (peripersonal space). In these cerebral areas some neurons are bimodal: they have tactile receptive fields on the face, and they can also be driven by visual stimuli located near the tactile field. The spatial correspondence between the visual and tactile receptive fields provides a map of near visual space coded in body-part-centred co-ordinates. In the present study we demonstrate for the first time the existence of a visual peripersonal space centred on the face in humans. In patients with right hemispheric lesions, visual stimuli delivered in the space near the ipsilesional side of the face extinguished tactile stimuli on the contralesional side (cross-modal visuotactile extinction) to the same extent as did an ipsilesional tactile stimulation (unimodal tactile extinction). Furthermore, a visual stimulus presented in the proximity of the contralesional side of the face improved the detection of a left tactile stimulus: i.e. under bilateral tactile presentation patients were more accurate to report the presence of a left tactile stimulus when a simultaneous visual stimulus was presented near the left side of the face. However, when visual stimuli were delivered far from the face, visuotactile extinction and visuotactile facilitation effects were dramatically reduced. These findings are consistent with the hypothesis of a representation of visual peripersonal space coded in bodypart-centred co-ordinates, and they provide a striking demonstration of the modularity of human visual space.

Event Abstract Back to Event Field potentials from macaque area V4 predict attention in single trials with ~100% accuracy David Rotermund1, Simon Neitzel2, Udo Ernst1*, Sunita Mandon2, Katja Taylor2, Yulia Smiyukha2 and Klaus Pawelzik1 1 University of Bremen, Department for Theoretical Physics, Center for Cognitive Sciences, Germany 2 University of Bremen, Department for Theoretical Neurobiology, Center for Cognitive Science, Germany Coherent oscillations and synchronous activity are suggested to play an important role in selective processing and dynamic routing of information across the primary visual cortical areas. In this contribution we show that local power spectral amplitudes and phase coherency between distant recording sites allow to distinguish almost perfectly between two attentional states in a behavioural task, thus giving strong quantitative support for a functional role of oscillatory neural dynamics. Macaque monkeys were trained to perform a delayed-match-to-sample task, in which the animals had to direct attention to one of two sequences of morphing shapes presented on a computer screen. The task was to signal the reoccurrence of the initial shape of the attended morphing sequence. Recordings of local field potentials (LFPs) were performed with an array of chronically implanted intracortical microelectrodes in one animal, and epidural recording arrays in two animals. These arrays covered parts of areas V1 and V4. We employed different stimulus sizes and configurations, ranging from 1 to 4 degrees in visual angle for the shape's diameters, and from 1 to 4 degrees visual angle in shape separation. The signals were split into their frequency components by applying a Morlet-wavelet transform. From the transformed data, we computed the phase coherency (i.e. a complex-valued scalar with amplitude <=1 and a phase difference) averaged over a time interval of 2500 ms, for every electrode pair. We then used a support vector machine (SVM) to classify the attended state (attention directed either to one or to the other sequence) from the power spectral amplitudes and mean phase differences between two recording sites. Strikingly, nearly perfect state identification (up to 99.9% correct) was possible from several pairs of electrodes in V4, mainly in the frequency bands of 48 Hz and 61 Hz. From V1-V4 electrode pairs, classification with up to 76% correct was possible. A similar performance was obtained using the spectral power of single electrodes in V4 in the Gamma frequency range. Our results show that power spectral amplitudes as well as phase differences between signals from V4 can accurately inform about the direction of attention to different locations in visual space in every single trial. This effect is robust against continuous changes of the shapes at the attended location. In addition, these findings are stable under the use of different recording techniques and various stimulus configurations, thus pointing to a key mechanism based on coherent oscillations for processing information under attention. Conference: Bernstein Conference on Computational Neuroscience, Frankfurt am Main, Germany, 30 Sep - 2 Oct, 2009. Presentation Type: Poster Presentation Topic: Information processing in neurons and networks Citation: Rotermund D, Neitzel S, Ernst U, Mandon S, Taylor K, Smiyukha Y and Pawelzik K (2009). Field potentials from macaque area V4 predict attention in single trials with ~100% accuracy. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference on Computational Neuroscience. doi: 10.3389/conf.neuro.10.2009.14.068 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Aug 2009; Published Online: 26 Aug 2009. * Correspondence: Udo Ernst, University of Bremen, Department for Theoretical Physics, Center for Cognitive Sciences, Bremen, Germany, udo@neuro.uni-bremen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers David Rotermund Simon Neitzel Udo Ernst Sunita Mandon Katja Taylor Yulia Smiyukha Klaus Pawelzik Google David Rotermund Simon Neitzel Udo Ernst Sunita Mandon Katja Taylor Yulia Smiyukha Klaus Pawelzik Google Scholar David Rotermund Simon Neitzel Udo Ernst Sunita Mandon Katja Taylor Yulia Smiyukha Klaus Pawelzik PubMed David Rotermund Simon Neitzel Udo Ernst Sunita Mandon Katja Taylor Yulia Smiyukha Klaus Pawelzik Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Alleys in visual space

Visual space perception has been a topic of sustained research since the nineteenth century. Much of this research into the geometry of visual space, however, required observers to make judgments about spatial relationships between isolated points in total darkness. While a sizeable number of previous investigations have now explored visual space perception in outdoor natural environments, nearly all of the previous investigations evaluating the curvature of visual space have utilized only small numbers of observers. In the current experiment, a large number (30) of observers adjusted triangular configurations of markers in an outdoor field until they appeared either as equilateral or right triangles in depth. There was a wide range of outcomes, such that the observers’ judgments were consistent with elliptic, Euclidean, and hyperbolic geometry. There is thus no single consistent relationship between physical space and perceived space. Furthermore, the geometry of visual space frequently changes as the size of spatial configurations is varied—for many observers, judgments for small configurations are consistent with elliptic or Euclidean geometry while judgments for large configurations are frequently consistent with hyperbolic geometry.

The mammalian visual cortex harbors a number of functional maps that represent distinct attributes of stimuli in the visual environment. How different functional maps are accommodated within the same cortical space, especially in species that show marked irregularities in one or more functional maps, remains poorly understood. We used optical imaging of intrinsic signals and electrophysiological techniques to investigate the organization of the maps of orientation preference, ocular dominance, and visual space in ferret. This species shows striking nonuniformity in the arrangement of ocular dominance domains and disruption of the mapping of visual space along the V1/V2 border. We asked whether these irregularities would be reflected in the organization of the map of orientation preference. The results show that orientation preference is mapped consistently within both V1 and V2, and across the interareal boundary, with no reflection of the irregularities in the other maps. These observations demonstrate the accommodation of multiple functional maps within the same cortical space without systematic geometrical relationships that necessarily constrain the organization of each representation. Furthermore, they imply that the structure of the map of orientation preference reflects the architecture and activity patterns of cortical circuits that are independent of other columnar systems established in layer 4.

The functional organization of intrinsic connections within area 18 of cat visual cortex was studied using combined electrophysiological and anatomical techniques. Physiological recordings were first used to map the distribution of orientation preference, ocular dominance, and receptive-field location relative to the cortical surface. Next, localized injections of lectin-conjugated horseradish peroxidase were made into physiologically identified regions within area 18. We found that (i) the local cortical interconnections are made preferentially between cell populations with orthogonal preferred orientations and are independent of the ocular dominance of the cortical cells, (ii) the map of visual space in the cortex is anisotropic with the magnification factor for vertical at least twice that for horizontal visual space, and (iii) the pattern of cortical projections compensates for the functional asymmetry so that a population of interconnected cells represents a roughly circular region of visual space.

Hexadirectional Modulation of High-Frequency Electrophysiological Activity in the Human Anterior Medial Temporal Lobe Maps Visual Space

We consider the shape of “visual space”. One immediate complication is that there are numerous “visual spaces”, often confused in the literature. Here we focus on visual awareness, rather than optically guided behavior, and “contemplative”, rather than “enactive” vision. Even so, the number of conceptually different “visual spaces” is appreciable. Important distinctions are between visual space as a rigid image of physical space, and visual space as an entity that depends critically upon an observer’s present state. For instance, in judging the relation between two locations, an observer may fixate one or the other. Conceivably, “visual space” will change the moment the observer swaps fixations. If that is indeed the case, then many of the conventional ways to address visual space, or to analyze raw psychophysical data, become effectively invalid. Here we re-analyze a number of available data-sets from such a perspective. We suggest that our notions of “the shape of visual space” need revision and re-investigation.KeywordsVisual SpaceVisual AwarenessSpace PictureFixed View PointObservational PictureThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Human vision is extremely sensitive to equidistance of spatial intervals in the frontal plane. Thresholds for spatial equidistance have been extensively measured in bisecting tasks. Despite the vast number of studies, the informational basis for equidistance perception is unknown. There are three possible sources of information for spatial equidistance in pictures, namely, distances in the picture plane, in physical space, and visual space. For each source, equidistant intervals were computed for perspective photographs of walls and canals. Intervals appear equidistant if equidistance is defined in visual space. Equidistance was further investigated in paintings of perspective scenes. In appraisals of the perspective skill of painters, emphasis has been on accurate use of vanishing points. The current study investigated the skill of painters to depict equidistant intervals. Depicted rows of equidistant columns, tiles, tapestries, or trees were analyzed in 30 paintings and engravings. Computational analysis shows that from the middle ages until now, artists either represented equidistance in physical space or in a visual space of very limited depth. Among the painters and engravers who depict equidistance in a highly nonveridical visual space are renowned experts of linear perspective.

We introduce a one-step implicit iterative method for two finite families of asymptotically nonexpansive mappings in a hyperbolic space and use it to approximate common fixed points of these families. The results presented in this paper are new in the setting of hyperbolic spaces. On top, these are generalizations of several results in literature from Banach spaces to hyperbolic spaces. At the end of the paper, we give an example to validate our results.

An approach to geometry of visual space with no a priori mapping functions: Multidimensional mapping according to Riemannian metrics

Results of experiments made under the scheme of the Luneburg's model in the author's laboratory were reviewed and were also discussed two fundamental postulates: Frameless binocular perceptual space as a Riemannian space of constant curvature K and the simple and rigid mapping functions between the physical space and the Euc1idean map of the perceptual space.Then, experimental results to embed perceptual configurations into a Euclidean space with the aid of the metric multidimensional scaling method were reviewed.In the last part, possibilities of testing the two fundamental postulates independently with each other and of incorporating into the model perturbation as to K and/or to the mapping functions were discussed.

The optic tectum (OT) of barn owls contains topographic maps of auditory and visual space. Barn owls reared with horizontally displacing prismatic spectacles (prisms) acquire a novel auditory space map in the OT that restores alignment with the prismatically displaced visual map. Although juvenile owls readily acquire alternative maps of auditory space as a result of experience, this plasticity is reduced greatly in adults. We tested whether hunting live prey, a natural and critically important behavior for barn owls, increases auditory map plasticity in adult owls. Two groups of naive adult owls were fit with prisms. The first group was fed dead mice during 10 weeks of prism experience, while the second group was required to hunt live prey for an identical period of time. When the owls hunted live prey, auditory maps shifted substantially farther (five times farther, on average) and the consistency of tuning curve shifts within each map increased. Only a short period of time in each day, during which the two groups experienced different conditions, accounts for this effect. In addition, increased map plasticity correlated with behavioral improvements in the owls' ability to strike and capture prey. These results indicate that the experience of hunting dramatically increases adult adaptive plasticity in this pathway.

The experiments described in this review have demonstrated that the SC contains a two-dimensional map of auditory space, which is synthesized within the brain using a combination of monaural and binaural localization cues. There is also an adaptive fusion of auditory and visual space in this midbrain nucleus, providing for a common access to the motor pathways that control orientation behaviour. This necessitates a highly plastic relationship between the visual and auditory systems, both during postnatal development and in adult life. Because of the independent mobility of difference sense organs, gating mechanisms are incorporated into the auditory representation to provide up-to-date information about the spatial orientation of the eyes and ears. The SC therefore provides a valuable model system for studying a number of important issues in brain function, including the neural coding of sound location, the co-ordination of spatial information between different sensory systems, and the integration of sensory signals with motor outputs.

Currently, with the development of public relations and production systems, there is a need to increase the capacity of communication systems and information transmission. It has been shown theoretically that it is possible to increase throughput by using multidimensional signals in space instead of real signals on a plane. It is now accepted that a multidimensional space, MultipleInput Multiple-Output (MIMO), can be formed using multiple antennas to transmit and receive in physical space. However, as physicists point out, such space is three-dimensional, and with the addition of time it is four-dimensional. It is clear that in such a physical space, when using more than 2 antennas for transmission and 2 for reception, it is impossible to obtain a gain in throughput of more than 4 times, since according to the laws of cybernetics, the diversity at the channel input will not be transmitted to the exit. It follows that it is necessary to reconsider existing views on the dimension of physical space. Previously, in the work the MIMO data transfer line with three-frequency quaternion carrier, it was shown that it is possible to use a hypercomplex quaternion number as a model of physical space. In this case, the dimension of space will be equal to 4 with 3 imaginary (spatial) axes and one scalar axis. In addition, combinations of three quaternion angular frequencies on the imaginary axes formed 4 single-frequency channels. Accordingly, the gain in throughput compared to real signals reached 4 in orthogonal axes and 4 in frequencies. In this work, an octonion with 7 imaginary (spatial) axes and one scalar is used as a mathematical model of physical space. It is shown that the dimension of physical space will be 8 with 64 single-frequency channels in the form of combinations of 7 angular frequencies. Hence, the gain in throughput will be 8 in orthogonal axes and 64 in frequencies.