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PubMed1975

Effects of posterior parietal and frontal neocortical lesions in the squirrel monkey.

Brightness discrimination, three forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were separated (SSP), delayed response, form discrimination, and three forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were identical (ISP) were given, in the order mentioned, to two groups of squirrel monkeys with frontal lesions were impaired on delayed response, and those with parietal lesions were impaired on form and SSP discriminations. Neither group was impaired on brightness discrimination. The results confirm and extend previous findings by other investigators that the posterior parietal cortex of nonhuman primates is critically involved in visually guided spatial discriminations when the primary cue and the site of reinforcement are separated.

Animals↗

PubMed1991

Optical mapping of the early development of the response pattern to vagal stimulation in embryonic chick brain stem.

1. In both intact and slice preparations of vagus-brain stem isolated from 3- to 8-day-old chick embryos, the spatial pattern of neural responses to vagal stimulation and its development were assessed by means of multiple-site optical recording of electrical activity, using a voltage-sensitive merocyanine-rhodanine dye (NK2761) and a 12 x 12-element photodiode array. 2. The first neural responses, viz. fast optical signals (related to the action potential), were recorded in the 4-day-old brain stem preparation, and slow optical signals (related to excitatory postsynaptic potentials) were detected from late 7- and 8-day-old brain stem preparations. 3. The evoked optical signals appeared to be concentrated longitudinally in the central region of the stimulated side of the intact brain stem preparation and in a limited dorsal area in the slice preparation. The signal size gradually increased and the response area expanded as development proceeded. 4. Based on the above results, we have constructed developmental maps of the spatial patterns of the fast and slow optical responses. In the maps, the positions of the peak-size regions of the fast and slow signals were assessed and we have found that there were differences in the location of these areas for the fast vs. the slow signals in the late 7- and 8-day-old embryonic brain stem preparations. 5. In the maps for the late 7- and 8-day-old embryonic brain stems, the fast signal response area seems to correspond to the dorsal motor nucleus of the vagus nerve and the slow response area to the nucleus tractus solitarii.

Action Potentials↗

PubMed1989

A novel spatial transcription pattern associated with the segmentation gene, giant, of Drosophila.

The segmentation gene, giant, is located in 3A1 within a cloned chromosome region surrounding the zeste locus. Rearrangement breakpoints associated with giant mutations were localized on the genomic clone map, and nearby transcription units were identified. One transcription unit is active during early embryogenesis and its transcripts are spatially localized from blastoderm into extended germband stages, consistent with expected expression patterns predicted by the 'gap' phenotype of giant mutants. Germ line transformation experiments using a 10-kb DNA fragment containing this transcription unit gave complete rescue of the abdominal giant defect but only partial correction of the head defect. The effect of mutations in three other gap loci, Kr, kni and hb, were also analyzed.

Alleles↗

PubMed1987

The organization of mesodermal pattern in Xenopus laevis: experiments using a Xenopus mesoderm-inducing factor.

In this paper, we study the mechanism by which a Xenopus cell line-derived mesoderm-inducing factor (MIF) might establish the spatial pattern of cellular differentiation in the mesoderm. The effects of the factor on competent animal pole tissue are consistent with it being identical to the natural mesoderm-inducing factor. The signal can only act on those membrane domains of the animal pole that face the blastocoel, but it can be stably recorded there, such that axial mesoderm is formed, after 15 min exposure or less. This exposure can end some hours, or several cell cycles, before the onset of RNA synthesis yet nevertheless be fully effective, although competence to respond also extends well after the onset of transcription. Exposure of the entire blastocoel lining of intact embryos to MIF causes a synchronous and sudden transformation of the behaviour and adhesive properties of all inner animal cap cells. This transformation mimics and is contemporaneous with the involution behaviour of normal mesoderm in the early gastrula marginal zone. Although high concentrations of MIF totally disorganize gastrulation, lower concentrations permit gastrulation to proceed. However, the pattern of mesoderm in these embryos is disrupted and ectopic mesoderm is formed around the blastocoel remnant. When MIF is injected directly into blastomeres, rather than into the blastocoel, it has no effect. This suggests that the molecule is secreted from source cells and affects target cells through an extracellular receptor. Finally, we show that small pieces of animal pole tissue recently exposed to MIF go on to produce morphogenetic signals perhaps distinct from MIF. We discuss the role of these signals in establishing and modifying the spatial pattern of cellular differentiation in the mesoderm of Xenopus.

Animals↗

PubMedDate not supplied

A spatial analysis of 100 surnames in England and Wales.

Spatial patterns are described and analysed for the 84 most common surnames in England and Wales, as well as 16 others selected for various reasons. At least three-quarters of the surname frequencies show spatial structure and are heterogeneous over the area of study. While they do not exhibit clines extending over the entire area of study, they do divide into four characteristics patterns. Spatial autocorrelation, while significant, is relatively low; similarity in surname frequency does not extend much beyond 100 km. Correlograms could be clustered to yield groups of surfaces denoting partial clines, isolation by distance, and differentiation at far distances. A method for detecting zones of rapid change found 21 such zones, mostly near the periphery of the study area. These boundaries do not indicate barriers to gene flow, but appear to be patterns brought about by historical factors. There are diffusion patterns between areas that differ greatly in surname composition, such as Wales and central England. There is little evidence of long-distance movements involving several surnames. At least three characteristic migration patterns, east-west and north-south diffusion and local dispersal, were found.

England↗

PubMed1979

EEG analysis gives model of neuronal template-matching mechanism for sensory search with olfactory bulb.

The spatial pattern of EEG activity at the surface of the olfactory bulb tends to be invariant with respect to input and to change to a new pattern whenever an animal is trained to expect or search for a particular odor. It is postulated here that the spatial EEG pattern is dependent on a neural template for that odor that is formed during training. This hypothesis is expressed in the form of a model consisting of an array of interconnected elements (1 X 10 or 6 X 6). Each element represents 2 excitatory and 2 inhibitory subsets of neurons with 3 types of internal feedback: negative, mutually excitatory, and mutually inhibitory. The elements are interconnected only by mutual excitation and mutual inhibition. Each neural subset is represented by a nonlinear differential equation; the connections are represented by modifiable coupling coefficients. With appropriate values of the time, coupling, and gain coefficients, and with input that is modelled on olfactory input, the set of 40 or 144 equations gives output that simulates the time and space patterns of the EEG. In the naive state the coefficients are uniform. A template is formed by giving input to selected elements, cross-correlating the outputs, and weighting the mutually excitatory coupling coefficient between each pair of elements by the corresponding correlation coefficient. When a template has been formed, input to nontemplate elements is treated as noise. Optionally a matched filter is made to simulate habituation by reducing the synaptic gain coefficients of those excitatory subsets that receive the noise. The model is tested by giving input to nontemplate elements and to none, part or all of the template elements. There are two outputs of the model. One is the spatial pattern Vj of the root mean square (rms) amplitudes of the individual outputs v(j, t) of the elements. The other output is the rms amplitude Erms of the ensemble average E(t) over v(j, t). The results show that Vj depends on the template and is relatively insensitive to input, whether or not input is given to template elements. However, Erms increases in proportion to the number of "hits" on the template. If the number of elements receiving noise does not exceed the number of elements in a template, or if the noise is matched with a habituation filter, then Erms rises above the noise level for a "hit" on any one or more template elements irrespective of location or combination. Vj conforms to the performance of the surface EEG. Erms is not yet accessible to physiological measurement.

Animals↗

PubMed1990

Flow patterns and spatial distribution of atherosclerotic lesions in human coronary arteries.

To investigate the potential role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in humans, the exact anatomic locations of atherosclerotic lesions and the flow patterns at such sites in left and right human coronary arteries were studied in detail by flow visualization and high-speed cinemicrographic techniques using five isolated, transparent human coronary arterial trees prepared postmortem. It was found that atherosclerotic plaques and wall thickenings in left and right coronary arteries were localized almost exclusively on the outer wall of one or both daughter vessels at major bifurcations and T-junctions, which left the flow-divider free of lesions, and along the inner wall of curved segments. When flow patterns in such vessels were studied in detail, it was discovered that these sites were where flow was either slow or disturbed with the formation of slow recirculation and secondary flows and where wall shear stress was low. The results indicate that the major hemodynamic factors directly related to the localization of atherosclerotic plaques and wall thickenings in the human arterial system are the low fluid velocity and the resultant low shear stress that acts on the vessel wall.

Adolescent↗

PubMed1986

Relation of olfactory EEG to behavior: time series analysis.

Oscillatory electroencephalographic bursts were measured from 64 electrodes implanted on the olfactory bulbs of rabbits. Oscillatory bursts that occurred before and during presentation of odorant conditioned stimuli (CSs) were selected in brief segments. Comparisons between the 64 traces and their spectra showed that, despite amplitude differences between channels, every burst had a common waveform over the entire array. The spectra showed 2 to 5 distinct peaks in each burst. Each trace was fitted with the sum of 5 cosines to express the burst in ten 8 X 8 matrices of amplitude and phase values at its peak frequencies. Two types of burst were identified. Those with dominant frequencies greater than 55 Hz had one narrow dominant spectral peak and reproducible spatial patterns of its amplitude within subgroups of bursts relating to control and odorant CS conditions. Those with dominant frequencies less than 55 Hz were disorderly; their spectra were broad, and their spatial patterns of amplitude did not reproduce within subgroups. A behavioral assay showed that the high- and not the low-frequency bursts contained odor-specific information.

Animals↗

PubMed1991

Ultrastructural and morphometric analysis of the separation of two thigh muscles in the chick.

Limb muscles separate from one another in a complex but highly stereotyped sequence and spatial pattern. The process of separation is characterized by the progression of a region of increased extracellular space, the cleavage zone, along the proximodistal axis between the individual muscle anlagen. We analyzed ultrastructurally the muscles and cleavage zone during the separation of two representative muscles, the developing sartorius and iliotibialis in the chick thigh, to establish an accurate baseline for an analysis of the mechanisms of separation. Comparisons of the morphology and distribution of cells before and after separation show no evidence that muscles became separated by the massive influx of an exterior cell population; if populations invade the cleavage zone, they are small. We do find characteristic transitions within the cell population of the cleavage zone in situ that could accomplish cleavage without invoking massive cell movements. These progressive transitions within the cleavage zone include a loss of close cell-cell interactions, an increase in extracellular space, the assumption of a more stellate morphology by mesenchyme cells, and a gradual alteration in the composition of the extracellular matrix from one typical of early muscle to one typical of loose connective tissue. Myotubes do differentiate between the incipient muscles, ruling out the possibility that the location where muscles will separate is defined by sites where myotubes fail to differentiate. Instead, the myotubes in the cleavage zone gradually diminish in number and appear to be specifically recognized and removed from the cleavage zone by phagocytes. We suggest that the transitions within the cleavage zone, including the loss of muscle cells, are a result of the progressive differentiation of loose connective tissue. If so, then the spatial pattern and process of cleavage is a consequence of spatially programmed cell differentiation.

Animals↗

PubMed1989

Developmental and environmental regulation of a phenylalanine ammonia-lyase-beta-glucuronidase gene fusion in transgenic tobacco plants.

A 1.1-kilobase promoter fragment of the bean (Phaseolus vulgaris L.) phenylalanine ammonia-lyase (EC 4.3.1.5) gene PAL2 was translationally fused to the beta-glucuronidase reporter gene and transferred to tobacco by Agrobacterium tumefaciens-mediated leaf disk transformation. The distribution of beta-glucuronidase activity in these transgenic plants is very similar to that of endogenous PAL2 transcripts in bean, with very high levels in petals; marked accumulation in anthers, stigmas, roots, and shoots; and low levels in sepals, ovaries, and leaves. Histochemical analysis of the spatial pattern of beta-glucuronidase activity showed that the PAL2 promoter is highly active in the shoot apical meristem, the zone of cell proliferation immediately adjacent to the root apical meristem, and in the early stages of vascular development at the inception of xylem differentiation. Wounding and light evoke specific changes in the spatial pattern of beta-glucuronidase activity in stems, including induction in the epidermis. These data indicate that the PAL2 promoter transduces a complex set of developmental and environmental cues into an integrated spatial and temporal program of gene expression to regulate the synthesis of a diverse array of phenylpropanoid natural products.

Ammonia-Lyases↗

PubMed1988

Mathematical simulation of proton tracks in water vapor and their microdosimetric analysis.

The spatial pattern of primary physical events was calculated for protons in water vapor by means of a Monte Carlo program. Two different cross section data sets were used to cover the proton energy range from 0.2 to 15 MeV. From the spatial pattern of primary energy deposition, proximity functions were derived and from these the dose mean lineal energy yD was calculated. The contributions of different track components to yD for spherical target volumes of 1-100 nm were analysed. The results are compared with the LET approximation and with analytical calculations of yD based on expectation values of the radial energy deposition around the proton path (radial dose profiles). Finally the associated volume of proton tracks was calculated using the so called 'linear approximation', and energy deposition distributions were derived. These were compared with distributions calculated by means of restricted-LET.

Algorithms↗

PubMed1986

Differentiation, cell sorting and proportion regulation in the slug stage of Dictyostelium discoideum.

Recent experimental work suggests that under normal conditions cell sorting plays an important part in maintaining and re-establishing the axial pattern of cell types in the slug stage of the cellular slime mold Dictyostelium discoideum. Following removal of the anterior zone of the slug, anterior-like cells that are normally distributed throughout the posterior of the slug rapidly migrate to the anterior end of the transected slug, and new anterior-like cells appear in the posterior portion. These results provide evidence that the direct linkage between spatial location and differentiation hypothesized in positional information models of spatial pattern formation is not universal. In this paper we develop and analyze a class of mathematical models of the slug in which cell determination can be less rigidly tied to spatial location, and which involve chemotactic cell sorting to re-establish and maintain the spatial pattern of cell types. We show that these models can reproduce the qualitative aspects of the experimental observations and that sorting takes place on the observed time scale when reasonable values of the parameters are used.

Cell Differentiation↗

PubMedDate not supplied

Visual discrimination of target displacement remains after damage to the striate cortex in humans.

Damage to the striate cortex usually causes blindness in those regions of the visual field which map to the area of neural damage. Nonetheless, there are reports that some patients with such damage can localize and perform certain visual discriminations between light stimuli presented within the 'blind' area of the visual field. Experiments on animals with different brain areas ablated suggest that visual function is served by two principal projection pathways from the retina. That to the striate cortex is primarily responsible for fine discrimination between stimulus parameters such as colour and spatial pattern, whereas that to the superior colliculus in the midbrain is responsible for visual localization of stimuli. The residual visual functions in patients with cortical damage are usually attributed to the non-striate retinal projection to the superior colliculus. We now present measurements of spatial discrimination in two observers with large visual field defects (scotomata) caused by damage to the striate cortical region. Both exhibit a near normal ability to discriminate displacements of targets when two lights are flashed sequentially in their defective visual field, but they are unable to discriminate spatial pattern or size. We argue that these results are consistent with the 'two visual systems' interpretation of ablation studies on non-human species.

Adult↗

PubMed1992

Changes in the cortical map of the hand following postnatal median nerve injury in monkeys: modification of somatotopic aggregates.

Median nerves to the hands of 8-15-d-old marmoset monkeys were transected and precluded from regeneration by ligation. Following periods of 0.4-1.5 years, features of organization in the cortical area 3b hand map were assessed neurophysiologically, and compared to features in normally reared monkeys. Cortical features in monkeys with both histories were similar in certain respects. (1) Receptive field organization was similar in terms of tactile thresholds and receptive field size, continuity, and glabrous-hairy specificity. (2) Somatotopic organization was similar in terms of the continuity of the glabrous representation, and progressions of receptive field shifts across some parts of the hand map. (3) Finally, the overall size of the hand map did not change. In contrast, other cortical features clearly differed following these developmental histories. (1) Neurons at virtually all recording sites in normal hand maps responded to light mechanical stimulation, whereas, following injury, neurons at about 8% of the recording sites responded only to high-intensity stimuli. (2) Somatotopic organization differed in terms of the presence or absence of the representation of skin autonomously innervated by the median nerve, the number and continuity of representations of hairy skin, and the spatial interfacing of representations. (3) Finally, there were differences in the areas and widths of representations of parts of the hand. The overall impression is that there is a correspondence between the cortical features that changed most after injury, and the features that varied most in individual normal monkeys: in both circumstances the most variable features involved properties of spatial patterning across large aggregates of neurons as reflected by the size, shape, continuity, and interfacing of representations. A hypothesis is proposed that suggests that the cortical hand map normally consists of a number of representations that are capable of developing and surviving somewhat autonomously of each other. The features of spatial patterning in the mosaiclike map of these representations are influenced by postnatal availability of inputs from intact hand nerves.

Animals↗

PubMed1990

Immunocytochemical study of S-100 positive glial cells in the brainstem and spinal cord of the rat embryo.

A light and electronmicroscopic immunocytochemical study of the glial cells in the brainstem and spinal cord of the 18th day rat embryo was performed using an anti-S-100 protein antiserum. Only the radial glia and the free immature glial cells are S-100 immunoreactive. Neurons are devoid of S-100 immunoreactivity. The radial glia form two paramedial plates and a great number of lateral plates, uniformly spaced along the ventral portion of the brainstem from the mesencephalon to the medulla. The S-100 protein was also detected in the perivascular membranes and glial limitans. Embryonic glia adopt a highly organized spatial pattern in the brainstem that could set the structural basis for an organized assembly of the developing nervous tissue. The use of the S-100 protein as a glial marker in the embryonic rat brain proved to be of great value. Antibodies to S-100 protein allow the demonstration of immature glial cells and a highly organized spatial pattern in the brainstem and spinal cord of the rat embryo.

Animals↗

PubMed1986

Responses of spatial mechanisms can explain hyperacuity.

A recently developed nonlinear mathematical model for spatial pattern discrimination, which is formally analogous to line element models in color vision, was applied to a variety of hyperacuity tasks. The computed results are in reasonable agreement with data on vernier acuity as a function of line length and separation, chevron acuity, periodic vernier acuity using sinusoidal lines, three line bisection acuity, vernier acuity using cosine gratings, and spatial interference with vernier acuity. In agreement with model predictions, data are presented showing that vernier acuity improves as a power function of contrast. It is concluded that the nonlinear, contrast dependent responses of visual mechanisms tuned for size and orientation can explain a wide range of hyperacuity and other spatial pattern discrimination tasks.

Discrimination, Psychological↗

PubMed1986

Two simple methods of spatial analysis and their applications in location-oriented health services research.

This paper illustrates the usefulness of cartographic and centrographic methods in examining the locational characteristics of health care resources, such as specialist physicians' offices. Cartographic analysis involving map comparisons not only describes the nature of particular spatial patterns, but it also suggests relevant hypotheses on the basis of observed locational relationships among the mapped phenomena. Centrographic analysis generally substantiates the findings of simple map analysis by providing certain objective quantitative measures regarding the basic characteristics of a point distribution; additionally, it generates a graphic summary, the Standard Deviational Ellipse (SDE), which offers a convenient means for direct comparison of multiple spatial patterns. The essentially complementary nature of the two methods is highlighted, and it is concluded that they are most useful when used in conjunction with one another.

Catchment Area, Health↗

PubMed1990

'Clustering'--real or apparent? Probability maps of childhood cancer in the West Midlands Health Authority region.

The West Midlands Regional Children's Tumour Registry collects detailed information on all cases of childhood cancer in the West Midlands Health Authority Region (WMHAR). The distribution by electoral ward of all cases diagnosed in the WMHAR between 1980 and 1984 has been determined. Analysis has also been performed for leukaemias/non-Hodgkin's lymphomas alone. We suggest that this latter grouping should be universally employed, owing to the difficulty of accurately separating out cases of leukaemia. Both spatial analyses showed several wards with significantly excessive rates on the basis of their cumulative Poison probability. Observed/expected ratios of 3-35 were seen for cases in significant wards, which are similar to the ratios seen in analysis of incidence around nuclear installations. However, further detailed consideration of these individual significance levels in the light of the number of statistically significant wards which would occur by chance alone, due to the multiple use of the test, accounted completely for the number of wards obtained in each of the groups considered. Thus, apparent 'clustering' of cases could be mere statistical artefact. In the WMHAR, therefore, using the technique of probability mapping, no true spatial pattern of incidence was found, other than that which would occur by chance alone. This, in a large area without nuclear installations and an even mix of rural and industrialised regions, could be seen as control data for those studies which have considered cases of childhood leukaemia around nuclear facilities, where the observation of single point clusters associated with suspected sites restricts assessments of spatial pattern in the rest of the area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗