Flat Map Research Articles

Multidirectional Projectional Rigid Neuro-Endoscopy: Prototype and Initial Experience

The role of neuro-endoscopy is emerging. Traditional endoscopy is complicated by limited 2D views that make surgical interventions difficult. We have developed a rigid endoscope with a variable direction view that provides 3D visualization. A prototype of the EndActive endoscope was used to examine 2 brain/intraventricular models. A 360-degree view is controlled via integrated joystick. Alternatively, the computer can volumetrically capture the ventricular surface. The captured video image can be viewed later or processed to create a flat projection map. The performance of this endoscope was compared to standard endoscopy with fixed directions of view. To simulate endoscopy, the center of the first brain model had eight labeled projections. The model was inspected with the multidirectional endoscope, standard rigid endoscopes (0-, 30- and 70-degree), and via a projection map. Ten neurosurgeons proficient in neuro-endoscopy were recruited for the experiments. The second brain model was labeled with 32 intraventricular tumors. With a 0-degree endoscope, only the number directly opposite the site of entry was visualized. With increasing angles, additional numbers were visualized. The 70-degree endoscope allowed 4 of 8 numbers to be visualized. Using the multidirectional endoscope, all 8 numbers were visualized. The multidirectional endoscope was more accurate in identifying markers compared to standard endoscopy (p = 0.031). The mean endoscopy times using the multidirectional endoscope and standard endoscopy were 143 and 117 seconds, respectively (p = 0.243). The best performance was obtained when the flat projection map was read (p < 0.01). Using the endoscope prototype, an average of 30.8 (96%) tumors was identified on the brain model. The EndActive endoscope is a rigid endoscope that provides complete visualization of a 3D space by controlling an adjustable viewing direction. In our study, the multidirectional endoscope provided superior visualization compared to standard endoscopy.

Cytology and functionally correlated circuits of human posterior cingulate areas

Human posterior cingulate cortex (PCC) and retrosplenial cortex (RSC) form the posterior cingulate gyrus, however, monkey connection and human imaging studies suggest that PCC area 23 is not uniform and atlases mislocate RSC. We histologically assessed these regions in 6 postmortem cases, plotted a flat map, and characterized differences in dorsal (d) and ventral (v) area 23. Subsequently, functional connectivity of histologically guided regions of interest (ROI) were assessed in 163 [ 18F]fluorodeoxyglucose human cases with PET. Compared to area d23, area v23 had a higher density and larger pyramids in layers II, IIIc, and Vb and more intermediate neurofilament-expressing neurons in layer Va. Coregisrtration of each case to standard coordinates showed that the ventral branch of the splenial sulci coincided with the border between d/v PCC at −5.4 ± 0.17 cm from the vertical plane and +1.97 ± 0.08 cm from the bi-commissural line. Correlation analysis of glucose metabolism using histologically guided ROIs suggested important circuit differences including dorsal and ventral visual stream inputs, interactions between the vPCC and subgenual cingulate cortex, and preferential relations between dPCC and the cingulate motor region. The RSC, in contrast, had restricted correlated activity with pericallosal cortex and thalamus. Visual information may be processed with an orbitofrontal link for synthesis of signals to drive premotor activity through dPCC. Review of the literature in terms of a PCC duality suggests that interactions of dPCC, including area 23d, orient the body in space via the cingulate motor areas, while vPCC interacts with subgenual cortex to process self-relevant emotional and non-emotional information and objects and self-reflection.

Cortical Representation of Space Around the Blind Spot

The neural mechanism that mediates perceptual filling-in of the blind spot is still under discussion. One hypothesis proposes that the cortical representation of the blind spot is activated only under conditions that elicit perceptual filling-in and requires congruent stimulation on both sides of the blind spot. Alternatively, the passive remapping hypothesis proposes that inputs from regions surrounding the blind spot infiltrate the representation of the blind spot in cortex. This theory predicts that independent stimuli presented to the left and right of the blind spot should lead to neighboring/overlapping activations in visual cortex when the blind-spot eye is stimulated but separated activations when the fellow eye is stimulated. Using functional MRI, we directly tested the remapping hypothesis by presenting flickering checkerboard wedges to the left or right of the spatial location of the blind spot, either to the blind-spot eye or to the fellow eye. Irrespective of which eye was stimulated, we found separate activations corresponding to the left and right wedges. We identified the centroid of the activations on a cortical flat map and measured the distance between activations. Distance measures of the cortical gap across the blind spot were accurate and reliable (mean distance: 6-8 mm across subjects, SD approximately 1 mm within subjects). Contrary to the predictions of the remapping hypothesis, cortical distances between activations to the two wedges were equally large for the blind-spot eye and fellow eye in areas V1 and V2/V3. Remapping therefore appears unlikely to account for perceptual filling-in at an early cortical level.

Architecture and neurocytology of monkey cingulate gyrus

Human functional imaging and neurocytology have produced important revisions to the organization of the cingulate gyrus and demonstrate four structure/function regions: anterior, midcingulate (MCC), posterior (PCC), and retrosplenial. This study evaluates the brain of a rhesus and 11 cynomolgus monkeys with Nissl staining and immunohistochemistry for neuron-specific nuclear binding protein, intermediate neurofilament proteins, and parvalbumin. The MCC region was identified along with its two subdivisions (a24' and p24'). The transition between areas 24 and 23 does not involve a simple increase in the number of neurons in layer IV but includes an increase in neuron density in layer Va of p24', a dysgranular layer IV in area 23d, granular area 23, with a neuron-dense layer Va and area 31. Each area on the dorsal bank of the cingulate gyrus has an extension around the fundus of the cingulate sulcus (f 24c, f 24c', f 24d, f 23c), whereas most cortex on the dorsal bank is composed of frontal motor areas. The PCC is composed of a dysgranular area 23d, area 23c in the caudal cingulate sulcus, a dorsal cingulate gyral area 23a/b, and a ventral area 23a/b. Finally, a dysgranular transition zone includes both area 23d and retrosplenial area 30. The distribution of areas was plotted onto flat maps to show the extent of each and their relationships to the vertical plane at the anterior commissure, corpus callosum, and cingulate sulcus. This major revision of the architectural organization of monkey cingulate cortex provides a new context for connection studies and for devising models of neuron diseases.

The CLASS Gravitational Lens Search

To exploit gravitational lensing for cosmology large, reliable and statistically complete surveys are required. With the Cosmic Lens All-Sky Survey (CLASS) we have set out to achieve these goals. We pre-select targets to be flat spectrum radio sources and map every source with the VLA at 200mas resolution. Candidates having multiple compact components with flux density ratios ≤10:1 and separation in the range 0.3 to 15 arcsec are followed up with high resolution MERLIN and VLBA observations, eliminating those candidates which do not match strictly defined surface brightness and morphological criteria. A complete sample of 11685 sources have been surveyed and nineteen lens systems have been found.

The Representation of Neural Data Using Visualization

Currently, the focus of research within Information Visualization is steering towards genomic data visualization due to the level of activity that the Human Genome Project has generated. However, the Human Brain project, renowned within Neuroinformatics, is equally challenging and exciting. Its main aim is to increase current understanding of brain function such as memory, learning, attention, emotions and consciousness. It is understood that this task will require the ‘integration of information from the level of the gene to the level of behaviour'. The work presented in this paper focuses on the visualization of neural data. More specifically, the data being analysed is multi-dimensional spike train data. Traditional methods, such as the ‘raster plot’ and the ‘cross-correlogram', are still useful but they do not scale up for larger assemblies of neurons. In this paper, a new innovative method called the Tunnel is defined. Its design is based on the principles of Information Visualization; overview the data, zoom and filter data, data details on demand. The features of this visualization environment are described. This includes data filtering, navigation and a ‘flat map’ overview facility. Additionally, a ‘coincidence overlay map’ is presented. This map washes the Tunnel with colour, which encodes the coincidence of spikes.

Donne's Nocturnal

In Donne's poem, A Nocturnall upon S. Lucies day, Being the shortest day,1 the word nocturnal is understood in the first place as 'night-piece' - the meaning given in the Oxford English Dictionary directly referring to this locus. 'Nightpiece', applied to a poem, is transferred from visual art: Ben Jonson uses the word to describe the cloudy back-cloth of his Masque of Blackness,2 and Webster, in the closing scene of The White Devil, makes Lodovico acknowledge his part in the tragedy as having 'limn'd this night-piece'.3 Herrick and Vaughan use the word in its transferred sense.4 Nocturnal, however, also carries a religious overtone as officium nocturnale, and may be found in this sense denoting the last service of the day. By analogy with such words as diurnal, ordinal - and even Herrick's trentall5 - used in a religious context, nocturnal takes on a solemn, ceremonious quality appropriate to the commemoration of St Lucy's Day, here marked - old style - as the shortest day of the year, the winter solstice. As St Lucy's name indicates, the saint, in the words applied to her by St Agatha, is 'indeed a light', but this is the day that contains the fewest daylight hours, and so must be considered the darkest of the year; the irony of what has been celebrated as a festival of light as the year reaches its nadir adds to the poignancy of the poem, Lucy its only light. Donne further emphasises the darkness of his spiritual annihilation by using the language of alchemy; the process of nigredo is a total reduction, marked by the repeated 'nothing' that particularises his desolate state.So far the language is richly layered, but there is a further dimension. In A Valediction, of Weeping, he had envisaged the world map, as it might be by Mercator's projection, as marvellously figuring the creation itself:On a round ballA workeman that hath copies by, can layAn Europe, Afrique and an Asia,And quickly make that, which was nothing, All.6It is a commonplace that the new discoveries of science inset in what had hitherto been the common stock of literate knowledge augmented poetic vocabularies in the sixteenth and seventeenth centuries, and Donne was able to draw upon the cabinet of curiosities opened up by new explorations and new philosophies. In a figure based on the effect of the moon on ocean tides, when the gravitational pull was observed but not understood, he develops his imagery out of the supposition (noted by Roger Bacon in his Opus Maius) that the moon's rays drew up vapours from the bottom of the sea, causing the ocean to swell. His hyperbolical image takes in legends of the Flood, whose limit was believed to touch the sphere of the moon; the attractions of the lady he addresses are deemed far in excess of the lunar powers:O more than MooneDraw not up seas to drowne me in thy Spheare7In a similar fashion, in the Hymne to God my God, in my sicknesse Donne exploits the new cartography by depicting the sick body as a cosmic map superimposed on a world map such as actual explorers might have used. The body-map marks out the journey of the soul towards the west, by tradition the place of death into which the sun nightly disappeared, but as the flat map curves round to follow the shape of the real world when pasted on a globe, the farthest west becomes the east, the Orient, from which the sun rises. The Orient is further identified with Christ, the dayspring, so that the journey towards death is a journey towards eternal life. The merging of east and west is similarly recorded in Goodfriday, 1613. Riding Westward:There I should see a Sunne, by rising set,And by that setting endless Day beget.8The language of Donne's Nocturnall relies heavily on the technical vocabulary of alchemy. But as Donne had used the physical imagery of the map to chart his spiritual journey towards death, cross-referencing the microcosm, man, with the macrocosm, the universe, so that the body of the dying man itself becomes the map, in this poem the state of the bereaved lover makes him the instrument by which the lowest point in the year is marked, the field shifted from earth to sky. …

Multireference object pose retrieval with volume feedback

Pose retrieval of a rigid object from monocular video sequences or images is addressed. Initially, the object pose is estimated in each image assuming flat depth maps. Shape-from-silhouette is then applied to make a 3-D model (volume), which is used for a new round of pose estimations, this time by a model-based method that gives better estimates. Before repeating this process by building a new volume, pose estimates are adjusted to reduce error by maximizing a novel quality factor for shape-from-silhouette volume reconstruction. The feedback loop is terminated when pose estimates do not change much, as compared with those produced by the previous iteration. Based on a theoretical study of the proposed system, a test of convergence to a given set of poses is devised. Reliable performance of the system is also proved by several experiments on both synthetic and real image sequences. No model is assumed for the object and no feature point is detected or tracked as there is no problematic feature matching or correspondence. Our method can be used for 3-D object tracking in video, 3-D modeling, and volume reconstruction from video.

Analysis of experimental time-resolved crystallographic data by singular value decomposition.

Singular value decomposition (SVD) separates time-dependent crystallographic data into time-independent and time-dependent components. Procedures for the effective application of SVD to time-resolved macromolecular crystallographic data have yet to be explored systematically. Here, the applicability of SVD to experimental crystallographic data is tested by analyzing 30 time-resolved Laue data sets spanning a time range of nanoseconds to milliseconds through the photocycle of the E46Q mutant of photoactive yellow protein. The data contain random and substantial systematic errors, the latter largely arising from crystal-to-crystal variation. The signal-to-noise ratio of weighted difference electron-density maps is significantly improved by the SVD flattening procedure. Application of SVD to these flattened maps spreads the signal across many of the 30 singular vectors, but a rotation of the vectors partitions the large majority of the signal into only five singular vectors. Fitting the time-dependent vectors to a sum of simple exponentials suggests that a chemical kinetic mechanism can describe the time-dependent structural data. Procedures for the effective SVD analysis of experimental time-resolved crystallographic data have been established and emphasize the necessity for minimizing systematic errors by modification of the data-collection protocol.

Délinéation des aires visuelles rétinotopiques chez le sujet individuel à l'aide de l'IRM fonctionnelle

Delineation of the retinotopic visual areas in the individual subject, using functional MR Imaging The methodology presented allows the delineation of primary visual areas by taking advantage of their retinotopic organization. Visual stimuli, which cover the visual field in a periodic fashion, are used. They induce, in the retinotopic areas, periodic activations measured by means of functional MRI. The visual-field sign changes between adjacent retinotopic areas. These changes may be detected in the phase maps obtained using Fourier analysis. The borders between adjacent areas are reconstructed on a flattened representation of the cortical ribbon. We present here such delineated flat maps generated on the basis of functional MRI experiments performed at 1.5 T. To cite this article: J. Warnking et al., C. R. Chimie 7 (2004).

Informatics approaches to functional MRI odor mapping of the rodent olfactory bulb: OdorMapBuilder and OdorMapDB.

The present study applies informatics tools to aid and extend fMRI analysis of the coding mechanism of neural signals in the rodent olfactory system. Odor stimulation evokes unique spatial patterns of activity in the glomerular layer of the mammalian olfactory bulb (OB). An open-source software program, OdorMap-Builder, has been developed to process the high resolution anatomical and functional MRI images of the OB and to generate single two-dimensional flat maps, called odor maps, that describe the spatial activity patterns in the entire glomerular layer. Odor maps help identify the spatial activity patterns from the tremendous amount of fMRI data and they serve as ideal representation of space coding for the olfactory signals in the OB in response to a given odor stimulation. Based on the fMRI technology, OdorMapBuilder provides comparable odor maps on the intra-subject basis, a significant step towards the detailed analyses of the effects of odor types and/or concentrations. In addition, a new database, OdorMapDB, is developed to provide a repository for the generated odor maps. Web interfaces to the database are provided for the data entry, modification and retrieval. OdorMapDB is based on the EAV/CR (entity-attribute-value with classes and relationships) architecture and it is integrated with two other SenseLab olfactory databases: the olfactory receptor and odor databases. Both OdorMapBuilder and OdorMapDB should serve as useful tools and resources for the field and help facilitate experimental research in understanding the olfactory system and the mechanism for smell perception.

Odor maps of aldehydes and esters revealed by functional MRI in the glomerular layer of the mouse olfactory bulb.

Odorant identity is believed to be encoded in the olfactory bulb (OB) by glomerular activity patterns. It has not yet been possible to visualize and compare entire patterns for different odorants in the same animal because of technical limitations. For this purpose we used high-resolution functional MRI at 7 T, combined with glomerular-layer flat maps, to reveal responses to aliphatic homologues in the mouse OB. These odorants elicited reproducible patterns in the OB, with the medial and lateral regions containing the most intense signals. Unexpectedly, in view of the symmetrical projections of olfactory receptor neurons to medial and lateral glomeruli, the activity patterns in these regions were asymmetrical. The highly activated medial and lateral areas were shared by homologous members, generating a conserved "family signature" for a homologous series. The moderately active areas, including the dorsal region that has been extensively studied by optical imaging, were more sensitive to the length of the carbon chain, producing more subtle features of individual members and different changing trends among homologues. The global mapping with functional MRI not only extended previous studies but also revealed additional rules for representation of homologues in the OB. Insights into possible relations between the functional patterns, molecular projections, and odor perception may now be obtained based on the global from the olfactory epithelium to the OB glomerular activity patterns.

Surround modulation measured with functional MRI in the human visual cortex.

Visual context profoundly influences 1) the responses of mammalian visual neurons and 2) the perceptual sensitivity of human observers to localized visual stimuli. We present data from functional MRI studies demonstrating contextual modulation in the human visual cortex. Subjects viewed a circular grating patch that was continuously present. A surround grating was added in an ON-OFF block design to reveal its effect on the central region. Stimulus-correlated activation was quantified and visualized on a flattened map of the occipital gray matter. Modulation was measured in a region of interest activated by the central grating alone. The observed effects were predominantly suppressive, consistent with the effects typically found in single neurons and perception. Suppression was greatest when the surround and center had the same orientation and was reduced or absent when it was orthogonal. When spatial phase was manipulated, suppression was greatest for in-phase center/surround gratings and much reduced or reversed (facilitation) for opposite-phase stimuli. With eccentric stimulus presentation, suppression was reduced and facilitation became more common. The findings provide a direct demonstration of the existence of powerful and stimulus-specific surround effects in human visual cortex.

Test ideals and base change problems in tight closure theory

Test ideals are an important concept in tight closure theory and their behavior via flat base change can be very difficult to understand. Our paper presents results regarding this behavior under flat maps with reasonably nice (but far from smooth) fibers. This involves analyzing, in depth, a special type of ideal of test elements, called the CS test ideal. Besides providing new results, the paper also contains extensions of a theorem by G. Lyubeznik and K. E. Smith on the completely stable test ideal and of theorems by F. Enescu and, independently, M. Hashimoto on the behavior of F F -rationality under flat base change.

Aesthetics Versus Functionality

Information Visualization (2002) 1, 93 – 94. doi:10.1057/palgrave.ivs.9500018 This is the second issue of our young journal. This issue continues what we started in the first issue – to provide an interdisciplinary forum for the field of information visualization. To shape the interdisciplinary forum, we continue to seek original and stimulating articles on a variety of topics that in one way or another contribute to the advancement of information visualization and have the potential to make a significant impact on our research agenda in the field. Contributions to this issue include one commentary and five original research articles towards the fulfillment of this goal. Aaron Marcus in his commentary article addresses a number of challenges which stemmed from the design of advanced vehicle information displays. He outlines these challenges in the broader context of information visualization and emphasizes their implications for information visualization beyond vehicle information displays. His article is entitled ‘Information Visualization for Advanced Vehicle Displays.’ The first research article in this issue is authored by Colin Ware, Helen Purchase, Linda Colpoys and Matthew McGill on cognitive measurements of graph aesthetics. Graph drawing is concerned with ways to depict a network algorithmically. Graph drawing algorithms typically rely on a set of aesthetic heuristics – rules that algorithms aim to optimize quantitatively. However, there have been few empirical studies of these aesthetic heuristics in the relevant literature. The authors of this article introduce a methodology for evaluating the cognitive cost of graph aesthetics and apply it to the task of finding the shortest paths in spring layout graphs, one of the widely known graph drawing algorithms in information visualization. They provide cognitive cost estimates for three important parameters: the length of the path, continuity, and edge crossings. The number of branches emanating from nodes on the path is also found to be important. The second research article is by Archana Sangole and George K. Knopf on representing high-dimensional data in a spherical self-organizing feature map (SOM). SOMs have a unique position in the history of information visualization. Traditionally, SOMs are represented in the form of a flat two-dimensional map. Sangole and Knopf present a three-dimensional color-coded surface model. They illustrate the use of their model with a small synthetic test data set and a large environmental database. Robert Spence addresses a wide-ranging question in the third research article: How should we design information visualization interfaces that would enable users to navigate effectively in information space? He introduces the concept of sensitivity encoding as part of his design guideline for navigation in information spaces. Sensitivity encoding is a feature of a data display. The goal of sensitivity encoding is to provide ‘road signs’ to guide users through information space. The fourth article is strongly application-oriented. Mohamed Sammouda, Rachid Sammouda, Noboru Niki and Kiyoshi Mukai describe a liver cancer detection system. The system can be used to analyze digitized color images of tissue samples obtained using needle biopsy. The key to the system is a combination of an unsupervised segmentation algorithm and an analysis algorithm based on image quantization. The segmentation Information Visualization (2002) 1, 93 – 94 a 2002 Palgrave Macmillan Ltd. All rights reserved 1473 – 8716 $15.00

Curved feature metrics in models of visual cortex

We study the relation between maps of a high-dimensional stimulus manifold onto an essentially two-dimensional cortical area and low-dimensional maps of stimulus features such as centroid position, orientation, spatial frequency, etc. Whereas the former safely can be represented in a Euclidean space, the latter are shown to require a Riemannian metric in order to reach qualitatively similar stationary structures under a standard learning algorithm. We show that the non-Euclidean framework allows for a tentative explanation of the presence of the so-called “pinwheels” in feature maps and compare maps obtained numerically in the flat high-dimensional maps and in the curved low-dimensional case.

Evaluating Conservation Practices Using GIS and Virtual Reality Modeling Language

In order for conservation practices to be installed most effectively,watershedplannersneedtoconsidernumerousfactors such as hydrology, topology, and farming practices. Flat maps, however, may not give decision-makers sufficient perspective to determine the best location for a particular conservation practice. Geographic information systems (GIS) and virtual reality modeling language (VRML) can be used to generate a three-dimensional environment for a watershed. This view identifies spatial relationships in the watershed and can help direct the planning, installation, and maintenance of conservation practices. This paper explains the usefulness of VRML in the promotion of properly placed best management practices (BMPs). A three-dimensional environment for the Lake Springfield Watershed, in central Illinois, was created using GIS and VRML. A30-mresolutiondigitalelevationmodel(DEM)wasutilizedas the base for creating the topological layer for the three-dimensional environment. Other spatial points of interest included slope, land use, hydrology, soil type, roads, and cropping type. An additional benefit of viewing an environment in three-dimensions is that it provides watershed groups with a visual inventory of existing BMPs. This can be used to highlight conservationachievementsanddemonstratetheneedforadditionalefforts.

Differing Map Construction and Text Organization and Their Effects on Retention

On the basis of Kulhavy's (R. W. Kulhavy, J. B. Lee, & L. C. Caterino, 1985) conjoint retention model of text learning with organized spatial displays, the authors conducted 2 experiments to analyze the effects of different types of maps and a considerate text (i.e., a text that follows the scanning pattern of the map) or an inconsiderate text. In the 1st study, 158 participants viewed an intact or a segmented map and a considerate or a randomized text. Those participants who viewed the intact map and read the considerate text recalled significantly more information than those who viewed the intact map and read the randomized text. In the 2nd study, 179 participants viewed a flat map, a 1-point perspective map, or a 2-point perspective map, and a considerate text formulated on the basis of the predicted scanning pattern of the map. Those participants who viewed the flat map recalled significantly more information than those who viewed the perspective maps.

Flattening and Subanalytic Sets in Rigid Analytic Geometry

Let K be an algebraically closed field endowed with a complete non-archimedean norm with valuation ring R. Let f: Y → X be a map of K-affinoid varieties. In this paper we study the analytic structure of the image f(Y) ⊂ X; such an image is a typical example of a subanalytic set. We show that the subanalytic sets are precisely the D-semianalytic sets, where D is the truncated division function first introduced by Denef and van den Dries. This result is most conveniently stated as a Quantifier Elimination result for the valuation ring R in an analytic expansion of the language of valued rings. To prove this we establish a Flattening Theorem for affinoid varieties in the style of Hironaka, which allows a reduction to the study of subanalytic sets arising from flat maps, that is, we show that a map of affinoid varieties can be rendered flat by using only finitely many local blowing ups. The case of a flat map is then dealt with by a small extension of a result of Raynaud and Gruson showing that the image of a flat map of affinoid varieties is open in the Grothendieck topology. Using Embedded Resolution of Singularities, we derive in the zero characteristic case, a Uniformization Theorem for subanalytic sets: a subanalytic set can be rendered semianalytic using only finitely many local blowing ups with smooth centres. As a corollary we obtain the fact that any subanalytic set in the plane R2 is semianalytic. 2000 Mathematical Subject Classification: 32P05, 32B20, 13C11, 12J25, 03C10.

Cytology of human caudomedial cingulate, retrosplenial, and caudal parahippocampal cortices.

Brodmann showed areas 26, 29, 30, 23, and 31 on the human posterior cingulate gyrus without marking sulcal areas. Histologic studies of retrosplenial areas 29 and 30 identify them on the ventral bank of the cingulate gyrus (CGv), whereas standardized atlases show area 30 on the surface of the caudomedial region. This study evaluates all areas on the CGv and caudomedial region with rigorous cytologic criteria in coronal and oblique sections Nissl stained or immunoreacted for neuron-specific nuclear binding protein and nonphosphorylated neurofilament proteins (NFP-ir). Ectosplenial area 26 has a granular layer with few large pyramidal neurons below. Lateral area 29 (29l) has a dense granular layer II-IV and undifferentiated layers V and VI. Medial area 29 (29m) has a layer III of medium and NFP-ir pyramids and a layer IV with some large, NFP-ir pyramidal neurons that distinguish it from areas 29l, 30, and 27. Although area 29m is primarily on the CGv, a terminal branch can extend onto the caudomedial lobule. Area 30 is dysgranular with a variable thickness layer IV that is interrupted by large NFP-ir neurons in layers IIIc and Va. Although area 30 does not appear on the surface of the caudomedial lobule, a terminal branch can form less that 1% of this gyrus. Area 23a is isocortex with a clear layer IV and large, NFP-ir neurons in layers IIIc and Va. Area 23b is similar to area 23a but with a thicker layer IV, more large neurons in layer Va, and a higher density of NFP-ir neurons in layer III. The caudomedial gyral surface is composed of areas 23a and 23b and a caudal extension of area 31. Although posterior area 27 and the parasubiculum are similar to rostral levels, posterior area 36' differs from rostral area 36. Subregional flat maps show that retrosplenial cortex is on the CGv, most of the surface of caudomedial cortex is areas 23a, 23b, and 31, and the retrosplenial/parahippocampal border is at the ventral edge of the splenium. Thus, Brodmann's map understates the rostral extent of retrosplenial cortex, overstates its caudoventral extent, and abridges the caudomedial extent of area 23.