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PubMed1992

The Critical Period for Experience-dependent Plasticity in a System of Binocular Visual Connections in Xenopus laevis: Its Temporal Profile and Relation to Normal Developmental Requirements.

A commissural system of 'intertectal' connections in Xenopus mediates the registration of binocular visual maps at the midbrain optic tectum. Following surgical eye rotation in larval animals, the system can completely alter its pattern of connectivity to restore binocular visual registration at the tectum. This experimentally induced plasticity is known to require visual experience and thought to be subject to an age-related restriction: eye rotation in adult animals is reported to provoke no subsequent intertectal alteration. In this paper we describe the detailed age-dependence of this plasticity. One eye was rotated in 238 animals of various developmental stages between mid-larval and adult life. At each age, different animals received rotations of different sizes, ranging from 20 to 180 degrees. The pattern of intertectal connectivity was mapped electrophysiologically 1 - 2 years postoperatively. A 'critical' period was defined around the time of metamorphosis: the vast majority of animals receiving a rotation in larval life (up to approximately 2 weeks before metamorphic climax) showed altered intertectal connections, whereas none of the animals operated upon at 3 months or more postmetamorphosis displayed the plasticity. At intervening ages, altered intertectal connections were found only in response to progressively smaller eye rotations. The profile of this critical period was further shown to mirror temporal features of the changes in eye position that occur in Xenopus as natural consequences of head growth, and which themselves impose a normal developmental requirement for intertectal plasticity. We conclude that the capacity of the Xenopus intertectal system for plasticity in response to abnormal experience undergoes a progressive age-dependent decline, and that the profile of this decline is delimited by normal requirements.

Journal Article↗
PubMed2004

RETRACTED: Synaptic changes in layer 2/3 underlying map plasticity of developing barrel cortex.

The functional and anatomical rearrangements of cortical sensory maps accompanying changes in experience are not well understood. We examined in vivo and in vitro how the sensory map and underlying synaptic connectivity of the developing rat barrel cortex are altered when the sensory input to the cortex is partially deprived. In the nondeprived cortex, both the sensory responses and synaptic connectivity between columns were strengthened through an increase in the synaptic connection probability between L2/3 pyramids in adjacent columns. This was accompanied by a selective growth of L2/3pyramid axonal arbors between spared columns. In contrast, deprived and nondeprived cortical columns became weakly connected in their L2/3 pyramid connections.

Action Potentials↗
PubMed1989

Intrinsic connections of rat primary visual cortex: laminar organization of axonal projections.

The organization of local projections within the rat primary visual cortex (area 17) was investigated by tracing fibers with HRP in in vitro brain slices. The projections from different layers showed distinct laminar patterns. Layer 4 made a strong, topographically precise, projection to lower layer 2/3; weaker projections extended laterally and terminated diffusely in layer 2/3 but also ran vertically to layers 5 and 6. The connections of lower and upper layer 2/3 were reciprocal and point-to-point. Within layer 2/3, a large number of fibers ran horizontally and terminated at variable distances from the injection site without making terminal clusters. The main output from layer 2/3 was to layer 5. The most prominent projections from the upper half of layer 5 were to layers 2/3 and 6; lower layer 5, in contrast, made wide-ranging, clustered projections to layer 1, the bottom of layer 2/3, and the top of layers 4 and 5. The patches were 130-160 micron wide and spaced apart by 230-260 micron. The main projection that arose from the superficial layer 6 terminated in layer 4 above the injection site. In contrast, lower layer 6 made clustered projections to the layer 3/4 border, extending up to 2 mm in the coronal plane. The patches were 190-220 micron wide and spaced apart by 320-390 micron. Additional projections went to the layer 5/6 border and layers 1 and 2. These results indicate that geniculocortical input is processed through interlaminar connections that are topographically precise, widespread, or patchy. These connectivity patterns suggest a role for these connections in the transformation of functional maps between layers; focused projections preserve the architecture of the layers of origin, and diverging or patchy projections rearrange this organization and form new maps in the target layers (Lund: Annu. Rev. Neurosci. 11:253-288, '88). However, only a few interlaminar connections show one of these patterns in isolation, making it difficult to assign a single function to a particular connection. We, therefore, tentatively conclude that projections terminating in layers 1-4, with the possible exception of the connection between upper layer 6 and layer 4, transform functional maps. In contrast, the topographically precise projections from upper to lower layers preserve functional maps. The specific role of these connections in the construction of receptive field properties, however, is not known.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Radiation hybrid map of the mouse genome.

Radiation hybrid (RH) maps are a useful tool for genome analysis, providing a direct method for localizing genes and anchoring physical maps and genomic sequence along chromosomes. The construction of a comprehensive RH map for the human genome has resulted in gene maps reflecting the location of more than 30,000 human genes. Here we report the first comprehensive RH map of the mouse genome. The map contains 2,486 loci screened against an RH panel of 93 cell lines. Most loci (93%) are simple sequence length polymorphisms (SSLPs) taken from the mouse genetic map, thereby providing direct integration between these two key maps. We performed RH mapping by a new and efficient approach in which we replaced traditional gel- or hybridization-based assays by a homogeneous 5'-nuclease assays involving a single common probe for all genetic markers. The map provides essentially complete connectivity and coverage across the genome, and good resolution for ordering loci, with 1 centiRay (cR) corresponding to an average of approximately 100 kb. The RH map, together with an accompanying World-Wide Web server, makes it possible for any investigator to rapidly localize sequences in the mouse genome. Together with the previously constructed genetic map and a YAC-based physical map reported in a companion paper, the fundamental maps required for mouse genomics are now available.

Animals↗
PubMed1992

Framework multipoint map of the long arm of human chromosome 4 and telomeric localization of the gene for FSHD.

Mapping the long arm of Chromosome (Chr) 4 has assumed medical relevance with the establishment of linkage of facioscapulohumeral muscular dystrophy (FSHD) to distal 4q markers. We have constructed a multipoint linkage map using DNA markers that map to the long arm of Chr 4. Segregation data were collected for 17 DNA markers on the multigenerational CEPH mapping families, and data for one marker were taken from the published CEPH database. Genotypic information for six of these markers was also collected from a set of 24 families that exhibited inheritance of FSHD. Multipoint analyses allowed us to construct a map of 12 loci, connecting two previously separate linkage groups. Significant sex-specific differences in recombination were found for some genetic intervals. Four loci from the distal region of this map showed linkage with FSHD. A map using these terminal markers gave the strongest support for FSHD in the most distal position over all other possible positions.

Chromosome Mapping↗
PubMed1993

Fibrillin genes map to regions of conserved mouse/human synteny on mouse chromosomes 2 and 18.

Fibrillin proteins are major structural components of the 10-nm microfibrils found in elastic and nonelastic connective tissues. Previous studies have mapped the human genes for two fibrillins to chromosome bands 15q21 (FBN1) and 5q23-q31 (FBN2) and have demonstrated that FBN1 mutations are associated with Marfan syndrome, while FBN2 is linked to the gene for congenital contractural arachnodactyly. Here, we report the isolation of genomic clones of the corresponding mouse fibrillin genes (Fbn-1 and Fbn-2). By analyzing a mapping panel of mouse x rodent somatic hybrid cell lines, we have assigned the Fbn-1 gene to mouse chromosome 2 and the Fbn-2 gene to mouse chromosome 18. We then sublocalized the fibrillin genes to bands 2F (Fbn-1) and 18D-E1 (Fbn-2) by fluorescence in situ hybridization. These regions are known to exhibit conserved synteny with the regions on human chromosomes 15 and 5 that carry the homologous human fibrillin genes. In addition, the Fbn-1 gene maps in the vicinity of the gene for a connective tissue disorder on mouse chromosome 2 called Tight-skin (Tsk).

Amino Acid Sequence↗
PubMed2006

Morphometric analysis of neuromuscular topography in the serratus anterior muscle.

Groups of neurons form ordered topographic maps on their targets, and defining the mechanisms that develop such maps, and re-connect them after disruption, has biological as well as clinical importance. The neuromuscular system is an accessible and well-studied model for defining the principles that guide map formation, both during its development and its reformation after motor nerve damage. We present evidence for the expression of this map at the level of nerve terminal morphology and muscle fiber type in the serratus anterior muscle. Morphometric analyses indicate, first, a rostrocaudal difference in nerve terminal size depending on the ventral root of origin of the axons. Second, motor endplates are larger on type IIB than type IIA muscle fibers. Third, whereas IIB muscle fibers are distributed rather evenly along the rostrocaudal axis of the muscle, the more rostral type IIB fibers are preferentially innervated by anteriorly derived (C6) motor neurons, and more caudal IIB fibers are preferentially innervated by posteriorly derived (C7) motor neurons. This inference is supported by analysis of the size of nerve terminals formed in each muscle sector by rostral and caudal roots, and by evidence that the larger terminals are on IIB fibers. These results demonstrate a subcellular expression of neuromuscular topography in the serratus anterior muscle (SA) muscle in the form of differences in nerve terminal size. These results provide deeper insights into the organization of a neuromuscular system. They also offer a rationale for a topographic map, that is, to allow spinal motor centers to activate selectively different compartments within a muscle.

Animals↗
PubMed2004

A genetic linkage map of grape, utilizing Vitis rupestris and Vitis arizonica.

A genetic linkage map of grape was constructed, utilizing 116 progeny derived from a cross of two Vitis rupestris x V. arizonica interspecific hybrids, using the pseudo-testcross strategy. A total of 475 DNA markers-410 amplified fragment length polymorphism, 24 inter-simple sequence repeat, 32 random amplified polymorphic DNA, and nine simple sequence repeat markers-were used to construct the parental maps. Markers segregating 1:1 were used to construct parental framework maps with confidence levels >90% with the Plant Genome Research Initiative mapping program. In the maternal (D8909-15) map, 105 framework markers and 55 accessory markers were ordered in 17 linkage groups (756 cM). The paternal (F8909-17) map had 111 framework markers and 33 accessory markers ordered in 19 linkage groups (1,082 cM). One hundred eighty-one markers segregating 3:1 were used to connect the two parental maps' parents. This moderately dense map will be useful for the initial mapping of genes and/or QTL for resistance to the dagger nematode, Xiphinema index, and Xylella fastidiosa, the bacterial causal agent of Pierce's disease.

Base Sequence↗
PubMed2002

Connectivity of features in microlens array reduction photolithography: generation of various patterns with a single photomask.

Microlens array photolithography (MAP) is a technique in which arrays of microlenses positioned close to photoresist reduce cm-sized figures on photomasks and form mum-scale images in the photoresist. This work demonstrates that MAP, using a single photomask, can generate patterns having different symmetries and periodicities from that of the lens array. This capability of MAP depends on (i) the connectivity between the images produced by individual microlenses and (ii) the orientation of the photomask relative to the lens array prior to exposure. By changing this orientation, MAP, using a single mask and a single array of microlenses, could be used to generate patterns that (i) are separated from each other, (ii) overlap with each other, (iii) are 2D chiral, and thus different from both the lens array and the mask in symmetry, (iv) have a symmetry reduced from that of the lens array, or (v) have a smaller unit cell and smaller pitch than that of the lens array.

Biological Assay↗
PubMed1996

Topography, architecture, and connections of somatosensory cortex in opossums: evidence for five somatosensory areas.

Microelectrode maps of somatosensory inputs were related to cortical architecture and patterns of cortical connections to provide evidence for five subdivisions of the somatosensory or sensorimotor cortex in North American opossums (Didelphis marsupialis). Microelectrode recordings revealed three systematic representations of the body surface. A large mediolaterally oriented representation was identified as the primary somatosensory area (S1) by its relative position, somatotopy, architecture, and connections. S1 represented the hindlimb, trunk, forelimb, and face in a mediolateral sequence. Two additional representations of cutaneous receptors were found caudolateral to S1, each with face representations adjacent to the border of lateral S1 and other body-part representations progressing more caudally toward the auditory cortex. We identified the more dorsal field as the second somatosensory area (S2) and the more ventral field as the parietal ventral area (PV). Tracers injected into S1 labeled neurons and terminals in architectonically distinct fields rostral and caudal to S1, the somatosensory caudal area (SC) and the somatosensory rostral area (SR). Movements could be evoked by microstimulation from sites scattered over S1, SR, and the frontal cortex, but thresholds were high and uncharacteristic of motor cortex. S2 and PV merged caudally with the cortex responsive to auditory stimuli, possibly A1, and neurons in some caudal recording sites in PV were activated by both auditory and cutaneous stimuli. Primary (V1) and secondary (V2) visual areas were also identified by microelectrode mapping, architecture, and connections. In addition, at least part of the cortex between V2 and the somatosensory cortex had visual connections. Thus, most of the dorsolateral cortex of opossums appears to be somatosensory, auditory, or visual.

Animals↗
PubMed2005

Visual shape recognition with contour propagation.

A neural architecture is presented that encodes the visual space inside and outside of a shape. The contours of a shape are propagated across an excitable neuronal map and fed through a set of orientation columns, thus creating a pattern which can be viewed as a vector field. This vector field is then burned as synaptic, directional connections into a propagation map, which will serve as a "shape map". The shape map identifies its own, preferred input when it is translated, deformed, scaled and fragmented, and discriminates other shapes very distinctively. Encoding visual space is much more efficient for shape recognition than determining contour geometry only.

Form Perception↗
PubMed2002

Latent learning, shortcuts and detours: a computational model.

Voicu and Schmajuk (Rob. Auto. Syst. 35 (2001a) 23) described a model of spatial navigation and exploration that includes an action system capable of guiding, with the help of a cognitive system, the search for specific goals as determined by a motivation system. Whereas in the original model the cognitive map stores information about the connectivity between places in the environment, in the present version the cognitive map also stores information about the paths traversed by the agent. Computer simulations show that the network correctly describes experimental results including latent learning in a maze, detours in a maze, and shortcuts in an open field. In addition, the model generates novel predictions about detours and shortcuts in an open field.

Journal Article↗
PubMedDate not supplied

Studies of cortical interactions over short periods of time during the search for verbal associations.

Interactions between cortical areas were studied during the search for verbal associations and reading of words. The functional anatomy and the sequence of involvement of cortical areas during the solution of these tasks have been described previously, in studies using positron emission tomography and multichannel recordings of evoked potentials combined with identification of the locations of dipole sources [8, 9, 19, 25]. Cortical interactions reflected in terms of the synchronization of EEG rhythms were studied by developing a method based on correlating curve wavelets, which allows the moments at which this synchronization occurs to be identified over short periods of time comparable with the speeds of individual thought operations (up to 100 msec). Three main stages were identified in the search for associations. During the first 200 msec after stimulus presentation, cortical connections were seen between the right and left frontal areas; at 200-500 msec, there were connections between the frontal and the temporal-parietal areas; finally, at 450-700 sec, there were connections between the left temporal and the right frontal-central-temporal areas. These results are in good agreement with data obtained previously using other methods and supplement them with mapping data on cortical connections. A number of differences in the mechanisms of information processing during the search for associations and reading were also identified.

Adolescent↗
PubMedDate not supplied

Mind-mapped care plans: a remarkable alternative to traditional nursing care plans.

Nursing care plans have helped students learn problem solving for nursing practice, but creativity and the interrelationship of patient problems are not stimulated by their linear nature. Joining mind mapping with care planning forces connections, engages whole brain thinking, and stimulates creativity. The authors describe mind mapping, infusion of mind-mapped care plans into the curriculum, the teaching/learning process of mapped care plans, and the positive outcomes of mind mapping nursing care plans.

Colorado↗
PubMed1993

Radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus.

BACKGROUND: The purpose of this study was to test the feasibility of radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus. METHODS AND RESULTS: Four patients who fulfilled criteria for having Mahaim fibers and preexcited reciprocating tachycardia underwent radiofrequency catheter ablation. Three patients had atriofascicular connections, and one patient had an atrioventricular connection. The mean age was 27 years (age range, 11-48 years). All patients had highly symptomatic tachycardias, producing syncope in one patient and presyncope in the remaining three patients. Symptoms were present for a mean of 13 years (range, 4-23 years). All pathways conducted only anterogradely, and preexcitation resulted in a left bundle branch block QRS morphology. Adenosine caused block in the accessory pathway in the three patients in whom it was tested. The stimulus to delta interval increased by 75 msec (range, 35-90 msec) during rapid atrial pacing. The atrial insertion of the Mahaim fiber was in the right lateral atrium in one patient, right posterolateral atrium in two patients, and right posterior atrium in one patient. The ventricular insertion was in the distal right bundle branch in three patients and in the posterolateral right ventricle near the tricuspid annulus in the patient with an atrioventricular connection. Stimulus to delta wave mapping was used to help localize the atrial insertion of the atriofascicular connections. A mean of 15 radiofrequency pulses (range, 10-19 pulses) delivered to the tricuspid annulus in the posterior to lateral regions eliminated accessory pathway conduction in all patients. No complications occurred. Tachycardia did not recur during a mean follow-up of 8 months (range, 2-15 months). CONCLUSIONS: Radiofrequency current applied to the tricuspid annulus can safely eliminate tachycardia in patients with Mahaim fibers.

Adolescent↗
PubMed2000

A dual-color FISH framework map for the characterization of the Sai1 tumor suppression region on rat chromosome 5.

The analysis of cell hybrids between malignant mouse hepatoma cells and normal rat fibroblasts has previously demonstrated the critical role of a deletion in rat chromosome 5 (RNO5) that was related to an anchorage independent phenotype. Those hybrids that were anchorage independent displayed loss of the entire RNO5 or an interstitial deletion in RNO5. These findings suggested that a putative tumor suppressor gene, Sai1 (suppression of anchorage independence 1), was located within the deleted region. To explore the molecular basis of the tumor suppressor activity of the Sai1 region, we analyzed the RNO5q23-q36 region with several genes and microsatellite markers that could be assigned to the region, as well as with new markers derived by representational difference analysis (RDA) or by microdissection. Dual-color FISH was used to construct a detailed physical map of the entire RNO5. These new data can be used to connect the physical and linkage maps in the rat, as well as to identify the details of the comparative map with other mammalian species including humans and mice. Using as FISH reagents genomic YAC, P1, or phage lambda clones corresponding to RNO5 markers, the order and unique positions of 18 markers could be established. The map provided a framework for the detailed characterization of the deletion found in anchorage independent hybrids. All markers within the bands RNO5q31.3-q35 were shown to be lost, including known cancer-related genes such as Ifna (5q32), Cdkn2a, -b (5q32), Jun (5q34), and Cdkn2c (5q35). However, the aberration in the deletion chromosome turned out to be more complex than originally thought in that we detected the presence of a paracentric inversion in addition to a deletion. The inversion led to the juxtaposition of the gene markers Tal2 (5q24.1) and Cd30lg (5q24.3). The framework map will provide the basis for the detailed physical YAC clone contig mapping of this region, and facilitate the identification and characterization of the Sai1 locus.

Animals↗
PubMed1992

Patterns of anomalous pulmonary venous connection/drainage in hypoplastic left heart syndrome: diagnostic role of Doppler color flow mapping and surgical implications.

Differentiation between anomalous connection and anomalous drainage of the pulmonary veins in hypoplastic left heart syndrome is important before either the Norwood procedure or heart transplantation is performed. To determine the prevalence of echocardiographically detected anomalous connection or drainage, or both, of pulmonary veins in patients with this syndrome, preoperative two-dimensional echocardiographic and Doppler color flow mapping studies of 317 patients who underwent the stage I Norwood procedure were reviewed. The term "connection" was used to describe the precise anatomic attachment of the pulmonary veins and the term "drainage" to describe the physiologic end point of pulmonary venous flow. Twenty patients (6.3%) had anomalous connection or drainage, or both, of the pulmonary veins by preoperative echocardiographic and Doppler examination. The subcostal and suprasternal scans best showed the anatomic details of the pulmonary veins. All these patterns were confirmed intraoperatively and could be grouped as follows: 1) partial anomalous connection and drainage (two patients); 2) total anomalous connection and drainage (eight patients); 3) normal connection with total anomalous drainage (eight patients); and 4) normal connection with partial anomalous drainage (two patients). The advantage of adding Doppler color flow mapping to two-dimensional echocardiography and conventional Doppler study was clearly demonstrated in the detection of small accessory vertical veins, their course and the presence or absence of obstruction. Doppler color flow mapping was especially helpful in detecting anomalous drainage of the right pulmonary veins to the right of the superior attachment of the septum primum.

Anastomosis, Surgical↗
PubMed2000

Functional specificity of callosal connections in tree shrew striate cortex.

Although callosal connections have been shown to link extensive regions of primary visual cortex, the distribution of these connections with respect to the map of visual space and the map of orientation preference remains unclear. Here we combine optical imaging of intrinsic signals with injection of fluorescent microspheres to assess the functional specificity of callosal connections in the tree shrew. By imaging both hemispheres simultaneously while presenting a series of spatially restricted stimuli, we find that a substantial region of visual space is represented bilaterally. Each hemisphere includes a representation of the ipsilateral visual field that is highly compressed relative to that of the contralateral visual field and is most extensive in the lower visual field, where approximately 30(o) of central visual space are represented bilaterally. Callosal connections extend throughout the region of bilateral representation but terminate in a spatially restricted manner that links visuotopically corresponding sites in the two hemispheres. In contrast, callosal connections appear to terminate without regard for the map of orientation preference, showing little sign of the orientation-specific modular and axial specificity that is characteristic of long-range horizontal connections. By coordinating the activity in the two hemispheres in a way that preserves nearest neighbor relationships, callosal connections may best be viewed as elements of local circuits that operate within a single bilateral representation of visual space.

Animals↗