Consistent mapping of orientation preference across irregular functional domains in ferret visual cortex.

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.

Simple and cost-effective hardware and software for functional brain mapping using intrinsic optical signal imaging

Orientation tuning and its dynamics of cat's primary visual cortex neurons located in pinwheel centers and orientation columns were studied during development of response in time. Functional domains in the Cortex were revealed by intrinsic signal optical imaging on functional and vascular maps of cortex. Both maps were used for precise placement of electrodes during recordings. Orientation tuning dynamic of each neuron was analyzed by temporary slices technique. Several types of neurons were observed in different functional domains: neurons with stable preferred orientation (14.5%); cells with preferred orientation dynamically shifted by 102 +/- 5 degrees (40.8%) and neurons with mixed dynamics type (44.7%). In pinwheel centers neurons with stable preferred orientation are differed from neurons with unstable preferred orientation in their features. In particular, they are showing greater response strength for preferred orientation. In orientation columns neurons with stable tuning are demonstrating larger latent periods for all orientations including preferred and non-preferred in comparison to cells with unstable response dynamics. We observed better detection quality of stable orientation neurons than in unstable preferred orientation neurons. Further coding features of neurons belonging to one functional type but located in different domains were compared. In general, located in pinwheel centers stable neurons have shorter latencies and stronger responses than for the stable cells located in orientation columns. Detection features were similar for this functional type of neurons. Unstable neurons located in different functional domains don't differ from each other in orientation tuning characteristics. Functional significance of neurons with stable and unstable preferred orientation located in pinwheel center and orientation columns in visual information processing are discussed.

Alleys in visual space

Event Abstract Back to Event Diminished plasticity of visual function and sensory maps after cortical stroke in mice Franziska Greifzu1*, Silvio Schmidt2, Friedrich Schmidt1, Otto W. Witte2 and Siegrid Löwel1 1 Friedrich-Schiller-University, Germany 2 University of Jena Medical School, Germany Stroke is a major cause of death and disability in the industrialized countries. It is an encouraging observation that clinically most patients who do suffer from stroke recover to some degree from the deficits which they incur. The most straightforward assumption is usually that this is due to plasticity. Many in vitro studies indicated that there is an increased plasticity in the perilesional zone of cortical infarcts. In the present study we investigated in vivo the impact of a photothrombotically induced cortical stroke on the plasticity of the neighbouring visual cortex after short periods of monocular deprivation (MD). Visual function was analyzed behaviourally with a virtual optomotor system. In addition, visual cortical maps were recorded using intrinsic signal optical imaging. After 7 days of MD, control animals showed a significant enhancement of visual acuity in the non-deprived eye and a significant ocular dominance shift towards the open eye in the optical imaging experiments. In contrast, in animals with a cortical stroke, both the enhancement of visual acuity and the ocular dominance shift were significantly lower. Thus our in vivo data rather indicate that neuronal plasticity is diminished in the surround of a cortical infarct. Conference: Bernstein Symposium 2008, Munich, Germany, 8 Oct - 10 Oct, 2008. Presentation Type: Poster Presentation Topic: All Abstracts Citation: Greifzu F, Schmidt S, Schmidt F, Witte OW and Löwel S (2008). Diminished plasticity of visual function and sensory maps after cortical stroke in mice. Front. Comput. Neurosci. Conference Abstract: Bernstein Symposium 2008. doi: 10.3389/conf.neuro.10.2008.01.052 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: 14 Nov 2008; Published Online: 14 Nov 2008. * Correspondence: Franziska Greifzu, Friedrich-Schiller-University, Jena, Germany, Franziska.Greifzu@uni-jena.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 Franziska Greifzu Silvio Schmidt Friedrich Schmidt Otto W Witte Siegrid Löwel Google Franziska Greifzu Silvio Schmidt Friedrich Schmidt Otto W Witte Siegrid Löwel Google Scholar Franziska Greifzu Silvio Schmidt Friedrich Schmidt Otto W Witte Siegrid Löwel PubMed Franziska Greifzu Silvio Schmidt Friedrich Schmidt Otto W Witte Siegrid Löwel 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.

Visual cortical neurons are sensitive to visual stimulus contrast and most cells adapt their sensitivity to the prevailing visual environment. Specifically, they match the steepest region of their contrast response function to the prevailing contrast (contrast gain control), and reduce spike rates to limit saturation (response gain control). Most neurons are also tuned for stimulus orientation, and neurons with similar orientation preference are clustered together into iso-orientation zones arranged around pinwheels, i.e. points where all orientations are represented. Here we investigated the relationship between the contrast adaptation properties of neurons and their location relative to pinwheels in the orientation preference map. We measured orientation preference maps in cat cortex using optical intrinsic signal imaging. We then characterized the contrast adaptation properties of single neurons located close to pinwheels, in iso-orientation zones, and at regions in between. We found little evidence of differential contrast sensitivity of neurons adapted to zero contrast. However, after adaptation to their preferred orientation at high contrast, changes in both contrast and response gain were greater for neurons near pinwheels compared with other map regions. Therefore, in the adapted state, which is probably typical during natural viewing, there is a spatial map of contrast sensitivity that is associated with the orientation preference map. This differential adaptation revealed a new dimension of cortical functional organization, linking the contrast adaptation of cells with the orientation preference of their nearest neighbours.

The development of both long-range intracortical and interhemispheric connections depends on visual experience. Previous experiments showed that in strabismic but not in normal cats, clustered horizontal axon projections preferentially connect cell groups activated by the same eye. This indicates that there is selective stabilization of fibers between neurons exhibiting correlated activity. Extending these experiments, we investigated in strabismic cats: (1) whether tangential connections remain confined to columns of similar orientation preference within the subsystems of left and right eye domains; and (2) whether callosal connections also extend predominantly between neurons activated by the same eye and preferring similar orientations. To this end, we analyzed in strabismic cats the topographic relationships between orientation preference domains and both intrinsic and callosal connections of area 17. Red and green latex microspheres were injected into monocular iso-orientation domains identified by optical imaging of intrinsic signals. Additionally, domains sharing the ocular dominance and orientation preference of the neurons at the injection sites were visualized by 2-deoxyglucose (2-DG) autoradiography. Quantitative analysis revealed that 56% of the retrogradely labeled cells within the injected area 17 and 60% of the transcallosally labeled neurons were located in the 2-DG-labeled iso-orientation domains. This indicates: (1) that strabismus does not interfere with the tendency of long-range horizontal fibers to link predominantly neurons of similar orientation preference; and (2) that the selection mechanisms for the stabilization of callosal connections are similar to those that are responsible for the specification of the tangential intrinsic connections.

Current trends in intraoperative optical imaging for functional brain mapping and delineation of lesions of language cortex

Optical imaging, PET and fMRI all rely on vascular responses to image neuronal activity. Although these imaging techniques are successfully used for functional brain mapping, the detailed spatio-temporal dynamics of hemodynamic events in the various microvascular compartments have remained unknown. Here, we used high-resolution optical imaging in area 18 of anesthetized cats to explore sensory-evoked blood-volume (CBV) changes in the various cortical microvascular compartments, selectively. To avoid the confounding effects of hematocrit and oximetry changes, we developed and used a new fluorescent blood plasma tracer and combined these measurements with optical imaging of intrinsic signals at a near-isosbestic wavelength for hemoglobin (565 nm). The vascular response began at the arteriolar level, rapidly spreading towards capillaries and venules. Larger veins lagged behind. Capillaries exhibited clear blood-volume changes. Arterioles and arteries had the largest response, whereas the venous response was smallest. Information about compartment-specific oxygen consumption dynamics was obtained in imaging sessions using 605 nm illumination, a wavelength known to reflect primarily oximetric changes, thus being more directly related to electrical activity than CBV changes. Those images were radically different: the response began at the parenchyma level, followed only later by the other microvascular compartments. These results have implications for the modeling of fMRI responses and suggest that the Balloon Model in its original formulation needs to be modified. Furthermore, functional maps obtained by imaging the capillary CBV response were similar but not identical to those obtained using the early oximetric signal, suggesting the presence of different regulatory mechanisms underlying these two hemodynamic processes.

Functional topography of single cortical cells: an intracellular approach combined with optical imaging

Early alcohol exposure disrupts visual cortex plasticity in mice

Cortical neurons with similar properties are grouped in columnar structures and supplied by matching vascular networks. The hemodynamic response to neuronal activation, however, is not well described on a fine spatial scale. We investigated the spatiotemporal characteristics of microvascular responses to neuronal activation in rat barrel cortex using optical intrinsic signal imaging and spectroscopy. Imaging was performed at 570 nm to provide functional maps of cerebral blood volume (CBV) changes and at 610 nm to estimate oxygenation changes. To emphasize parenchymal rather than large vessel contributions to the functional hemodynamic responses, we developed an ANOVA-based statistical analysis technique. Perfusion-based maps were compared with underlying neuroanatomy with cytochrome oxidase staining. Statistically determined CBV responses localized accurately to individually stimulated barrel columns and could resolve neighboring columns with a resolution better than 400 microm. Both CBV and early oxygenation responses extended beyond anatomical boundaries of single columns, but this vascular point spread did not preclude spatial specificity. These results indicate that microvascular flow control structures providing targeted flow increases to metabolically active neuronal columns also produce finely localized changes in CBV. This spatial specificity, along with the high contrast/noise ratio, makes the CBV response an attractive mapping signal. We also found that functional oxygenation changes can achieve submillimeter specificity not only during the transient deoxygenation ("initial dip") but also during the early part of the hyperoxygenation. We, therefore, suggest that to optimize hemodynamic spatial specificity, appropriate response timing (using < or =2-3 sec changes) is more important than etiology (oxygenation or volume).

A laminar model for the joint development of ocular dominance columns and CO blobs in the primary visual cortex

How does the brain represent and process color in the primary visual cortex (V1)? Experimental evidence from macaque monkey suggests that cells selective for color are organized into small, spatially separated blobs in V1. This organization is strikingly different from that of orientation and ocular dominance maps, which consist of large, spatially contiguous patterns. In this paper, a self-organizing tri-chromatic model of V1 is constructed using natural color image input. Neurons in the modeled V1 are initially unselective, and develop multi-lobed ON/OFF receptive fields through Hebbian learning of retinal responses to visual patterns. The model develops realistic color-selective receptive fields, color maps, ocular dominance columns, and orientation maps. Color-selective blobs are located inside ocular dominance columns, and lateral connections link cells with similar orientation preferences, matching previous experimental results. Further, the model makes a number of predictions for future experiments, including: 1. The color map has three types of color-selective blobs and a unique cortical activation pattern exists for each of the pure color hues. 2. The usual blob-like organization for color emerges as long as the training images have a higher brightness contour gradient compared to the hue contour gradient, and the inputs are highly correlated between the eyes. Otherwise the color blobs regularly extend across borders of ocular dominance stripes (contrary to macaque results). 3. Neurons in areas where red and green patches are near each other respond to both red and green, causing them to maximally prefer yellow, even though there are no yellow photoreceptors in the retina. 4. Cells selective for color connect to other cells with similar chromatic preferences: Blue-selective neurons connect to blue selective neurons, red-selective to other red-selective neurons, and so forth. Thus the model replicates the known data on the organization of color selectivity in V1, gives a detailed explanation for how this structure develops and functions, and provides concrete predictions that can be tested in future experiments. These findings suggest that a single self-organizing system may underlie the development of orientation selectivity, eye preference, color selectivity, and lateral connectivity in the primary visual cortex.

The deeper layers of the mammalian superior colliculus (SC) contain a two-dimensional map of auditory space, which is in register with maps of visual space and of the body surface (King and Carlile, 1995; Stein and Meredith, 1993). This arrangement facilitates the integration of multisensory signals from particular positions in space and the guidance of orientation movements toward both unimodal and multimodal targets. In contrast to the visual and somatosensory maps, which arise from the topographic arrangement of axons leaving their respective receptor surfaces, the map of auditory space has to be computed centrally by neurons that are differentially sensitive to the acoustic localization cues that result from the interaction of sound with the ears and head (King and Carlile, 1995).