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At least 19 recordsLinked to original sources

PubMed1983

Spatiotemporal variation of chromatic and achromatic contrast thresholds.

Moving the retinal image of a sinusoidal grating at a constant velocity (compensated for eye movements) provides controlled spatial and temporal frequencies at every point in the stimulus field. Using this controlled-velocity technique, we have measured the detection threshold for isoluminance, red/green gratings as a function of their spatial and temporal frequencies. The chromatic contrast-threshold surface obtained in this way is analogous to the achromatic contrast-threshold surface measured previously, but the results are quite different. For very low temporal frequencies (below 0.2 Hz), the chromatic sensitivity decreases steadily with decreasing temporal frequency. Below 0.01 Hz, chromatic patterns disappear completely even at maximum contrast (although achromatic or homochromatic patterns do not). In the region above 0.2 Hz, both achromatic and chromatic thresholds can be explained by the same receptive-field-like model. When the center and the surround components of this model are additively combined, they form the chromatic threshold surface; when the sign of either component is reversed, they form the achromatic one.

Color Perception↗

PubMed1992

Myosin heavy chain expression in rabbit masseter muscle during postnatal development.

The expression of isoforms of myosin heavy chain (MHC) during postnatal development was studied in the masseter muscle of the rabbit. Evidence is presented that in addition to adult fast and slow myosin, the rabbit masseter contains neonatal and 'cardiac' alpha-MHC. During postnatal growth myosin transitions take place from neonatal and fast (IIA, IIA/IIB--referring to a fibre containing both IIA and IIB MHCs) MHC to adult 'cardiac' alpha-MHC and I/alpha-MHC. Since there is a temporary population of fibres containing IIA/alpha-MHC during the first 4 wk of development with a peak in the 3rd to 4th wk, the transition from IIA-MHC to alpha-MHC may occur in these IIA/alpha-MHC-containing fibres. The appearance of 'cardiac' alpha-MHC coincides with the timing of weaning, suggesting that the changes in MHC content, that probably result in a transition to a lower speed of contraction, have functional significance related to weaning. The finding of neonatal MHC in adult rabbits indicates that the masseter develops at a rate and in a way that is distinct from most other skeletal muscles. A spatiotemporal variation in expression of myosin isozymes within the masseter was observed, with many fibres containing more than one myosin type, indicating developmentally regulated spatial differences in function.

Adenosine Triphosphatases↗

PubMed2026

The Charcot-Marie-Tooth Neuropathy (CMTX3) Complex Structural Variation Causes Differential SOX3 Spatiotemporal Expression.

Charcot-Marie-Tooth (CMT) neuropathy is a clinically and genetically heterogeneous group of diseases characterized by the length-dependent axonal degeneration of peripheral nerves. We previously mapped a rare form of X-linked CMT, CMTX3, to a 5.7-Mb interval on chromosome Xq26.3-q27.1 and excluded the coding region of all known genes in the linkage interval for mutations. Whole genome sequencing subsequently identified a 78-kb region of chromosome 8q24.3 that had been duplicated and inserted into the CMTX3 locus between the genes HAPSTR2 and SOX3. The 78-kb insertion, which contains a partial transcript of ARHGAP39, fully segregated in families with CMTX3 and was absent in neurologically normal controls. To retain the CMTX3 insertion and investigate its consequences in appropriate neuronal tissue, we generated induced pluripotent stem cells (iPSCs) from CMTX3 fibroblasts. Using bulk RNA sequencing of patient-derived spinal motor neurons, ARHGAP39 was deemed nonpathogenic by excluding both the formation of novel fusion transcripts and dosage effects from the partial duplication. Subsequent NanoString expression analyses of candidate genes within the CMTX3 locus, across different stages of neuronal differentiation, identified spatiotemporal dysregulation of SOX3. NanoString showed reduced SOX3 expression in patient iPSCs. RNA sequencing detected SOX3 downregulation in CMTX3 neuroepithelial progenitor cells, which was further confirmed by quantitative proteomics. Given the early onset and relatively rapid progression of CMTX3, these data prioritise SOX3 as a leading candidate gene, consistent with its role as one of the earliest transcription factors expressed in the developing nervous system and a key regulator of neuronal fate.

Humans↗

PubMed2025

Tracking microplastic contamination across seasons in a freshwater reservoir: Evidence from surface water, sediments, and fishes.

Microplastics (MPs) are prevalent contaminants in aquatic environments, posing substantial ecological and health risks. These particles migrate within the different layers of aquatic bodies with time and affect the respective biota. Thus, to get an in-depth understanding of the particles, this current study investigated the seasonal distribution, morphological and chemical characteristics, along with potential ecological and human health impacts in the samples including surface water, sediment, and fish from a drinking water supplying reservoir in eastern India. Across three different seasons, pre-monsoon, monsoon, and post-monsoon samples were collected using optimized methods. Results revealed distinct seasonal trends: MP abundance in surface water peaked during the monsoon (mean: 1.15 MPs/L), while sediment showed the highest concentrations in the pre-monsoon (mean: 596 MPs/kg), indicating temporal accumulation dynamics influenced by runoff, hydrodynamics, and sedimentation. Fish gut analysis confirmed ingestion of MPs across five species, with concentrations ranging from 26 to 100 MPs/kg, depending on feeding habits. The most dominant MP type were fragments, followed by fibers, films, and beads. Polymer analysis via µFTIR identified polyethylene, polypropylene, and polyvinyl chloride as prevalent, with hazard assessments (i.e., Polymer Hazard Index (PHI)) indicating medium to very high ecological risks. Heavy metal association was more dominant in the MPs isolated from sediments than the waterborne MPs. Pollution Load Index (PLI) values were > 1 in most seasons, confirming contamination. Health risk analysis suggested potential exposure through both drinking water and fish consumption. This study emphasizes the need for seasonal monitoring, improved waste management, and mitigation strategies to address MP pollution in freshwater ecosystems.

Microplastics↗

PubMed1988

The development of grooming and its expression in adult animals.

We have seen that grooming is a class of heterogeneous activities, widely represented in animal taxa, yet sufficiently homogeneous within some phyletic groups to generate and test phylogenetic hypotheses. In the life of the grooming animal, the functions served by these activities are also diverse. Similar acts of grooming may serve different functions in different species or in different contexts. Sometimes these different functions can be discovered by careful attention to variations in the spatiotemporal patterning or sequencing of grooming elements. In several species a general cephalocaudal progression has been noted during both the ontogeny of grooming and during its expression in adults. During early development and in adulthood, the components or functional units of grooming appear to be hierarchically organized. Scratching with the hindpaw, for example, appears in rodents to be separate from the hierarchical branches in which one finds licking and face wiping. At least some transitions between functional units can be predicted from changes in the temporal patterning of one grooming unit (e.g., eye wipe) just prior to the onset of another unit (e.g., ear wipe). Analyses of genital and other types of grooming during two forms of sexual activity (copulation and the display of penile erections ex copula) were used to demonstrate once again that the stimulus regulation of grooming is context dependent. Among the implications of this review for the physiological study of grooming are the following: 1. Careful attention should be given to the spatiotemporal patterning of grooming, in order to reduce errors of "lumping" and "splitting" in classifying grooming acts, and also to detect alterations in the patterning when they occur. Such changes in patterning may be assumed to reflect changes in the physiological state of the animal. 2. Grooming acts that appear formally similar in different contexts may operate under rather different physiological systems. 3. Experimental manipulations may affect grooming directly, that is, by generating grooming efference without changing afference, or indirectly, by altering the "motivational state" or by creating stimulation that potentiates grooming, as from itching or from reafference due to provoking other behavior patterns.

Aging↗

PubMed1992

Spatiotemporal irregularities of spiral wave activity in isolated ventricular muscle.

Voltage-sensitive dyes and high resolution optical mapping were used to analyze the characteristics of spiral waves of excitation in isolated ventricular myocardium. In addition, analytical techniques, which have been previously used in the study of the characteristics of spiral waves in chemical reactions, were applied to determine the voltage structure of the center of the rotating activity (ie, the core). During stable spiral wave activity local activation occurs in a periodic fashion (ie, 1:1 stimulus: response activation ratio) throughout the preparation, except at the core, which is a small elongated area where the activity is of low voltage and the activation ratio is 1:0. The voltage amplitude increases gradually from the center of the core to the periphery. In some cases, however, regular activation patterns at the periphery may coexist with irregular local activation patterns near the core. Such a spatiotemporal irregularity is attended by variations in the core size and shape and results from changes in the core position. The authors conclude that functionally determined reentrant activity in the heart may be the result of spiral waves of propagation and that local spatiotemporal irregularities in the activation pattern are the result of changes in the core position.

Animals↗

PubMed1983

Suprathreshold spatiotemporal response characteristics of the human visual system.

The apparent contrasts of suprathreshold stationary gratings, countermodulated gratings, and homogeneous flickering fields were assessed with a contrast-matching procedure. Results show that, as stimulus amplitude is increased relative to threshold, variations in apparent contrast with spatiotemporal-frequency content become much less pronounced. In other words, the contrast-matching functions are more uniform across both spatial and temporal frequency at levels of contrast well above threshold. These data are interpreted in terms of a compensatory stage in the visual system that varies its gain characteristics according to the detectability of the stimulus.

Differential Threshold↗

PubMed2026

Effects of an actuated ankle exoskeleton on walking stability in healthy adults: a controlled laboratory study.

BACKGROUND: Ankle exoskeletons are widely used to reduce the metabolic cost of walking, yet their effects on walking stability during unperturbed gait remain insufficiently understood. Walking stability can be characterized using complementary measures that capture stride-to-stride variability, global temporal organization, and local dynamic stability. Understanding how walking with an actuated ankle exoskeleton system influences these different aspects of gait stability is essential for the safe design and control of wearable robotic devices. METHODS: Eighteen healthy adults walked on a treadmill at a constant speed (1.1 m/s) with and without an actuated bilateral ankle exoskeleton in a randomized crossover design. Spatiotemporal variability was quantified using coefficients of variation (CoV) of stride length, step width, and stance ratio. Global gait stability was assessed using detrended fluctuation analysis of stride time. Local dynamic stability was evaluated using maximum Lyapunov exponent calculated for the trunk, hip, upper leg, lower leg, and foot. Paired-samples two-sided t-tests were used to compare conditions. RESULTS: Walking with the ankle exoskeleton resulted in increased stride-to-stride spatiotemporal variability, reflected by higher CoV values for stride length (p < 0.001) and stance ratio (p = 0.005), while mean stride length and step width remained unchanged. Mean stance ratio was reduced in the exoskeleton condition (p < 0.001). Global gait stability did not differ between conditions, indicating preserved long-range temporal gait organization. Local dynamic stability increased at the lower leg (p < 0.001) and foot (p = 0.019) when walking with the exoskeleton. CONCLUSIONS: Walking with the actuated ankle exoskeleton alters gait control across multiple levels during steady walking. While stride-to-stride variability in stride length and stance ratio increased, global gait stability remained unchanged. Local dynamic stability was increased at the lower leg and foot, suggesting segment-specific effects of ankle-level assistance close to the assisted joint. However, these findings should be interpreted as the combined effect of wearing the exoskeleton and receiving active assistance, rather than the isolated effect of plantarflexion assistance. These results provide insight for the design and control of ankle exoskeletons with respect to stability-related effects during walking.

Humans↗

PubMed1990

Simulation of motion on the skin. III. Mechanisms used by rapidly adapting cutaneous mechanoreceptors in the primate hand for spatiotemporal resolution and two-point discrimination.

1. The contribution of rapidly adapting (RA) mechanoreceptors to two-point discrimination has been evaluated by examining their ability to resolve the spacing of grating patterns shifted across the skin. The experiments test two different neural coding mechanisms that have been proposed to underlie resolution of spatial detail on the hand: 1) a rate-intensity code in which the spacing of surface features is encoded by the average frequency of firing of individual sensory afferents, and 2) an isomorphic representation of shape in which variations in the firing patterns of individual afferents reflect the spatiotemporal profile of skin indentation. 2. To measure the spatial acuity of RA mechanoreceptors innervating the hands of macaque monkeys, we displayed pairs of horizontal bars spaced 1-13 mm apart on a computer-controlled OPTACON stimulator placed over glabrous skin. Two-point resolution was measured by simultaneously pulsing pairs of rows at rates of 100, 50 and 25 Hz; each pair was shifted in tandem across the hand to simulate lateral motion. Single-fiber recordings were made from physiologically identified RA afferents in anesthetized monkeys. 3. Receptive field diameter appears to be the critical determinant of spatial resolution of gaps between two bars. RAs fire continuously if bar spacing is less than the field diameter but do not summate inputs when both active rows are contained within the field. Response profiles evoked by two bars spaced less than 4.8 mm apart can be predicted from the single-bar profiles, assuming occlusion between overlapping inputs with the strongest member dominating axonal output. Two-thirds of the RAs tested discharge 1 spike/pulse as bar patterns cross the field, yielding a uniform spike train whose frequency reflects stimulus pulse rates but fails to indicate gaps between bars. An additional 17% fire 2 spikes/pulse when the bars contact or straddle the field center, but also fail to differentiate individual stripes spaced less than 3.6 mm apart. 4. Only 17% of RAs represent gaps narrower than the field diameter. These fibers show double-peaked response profiles to bar patterns spaced at least 2.4 mm apart, firing 2 spikes/pulse as first one, and then the second stripe crosses the field center. Timing between peaks corresponds to bar spacing. Responses are reduced in amplitude when adjacent bars straddle the field center, as occlusion between simultaneous inputs prevents summation of inputs from the two stimuli. Fifteen of 16 RAs failed to resolve bars spaced 1.2 mm apart, as double-spike responses were evoked only by the leading stripe.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1984

Effects of disturbed sleep on contingent negative variation.

To understand better the pathophysiological aspects of disturbed sleep, six healthy male students underwent a series of sleep recordings. On the experimental night, subjects' sleep was disturbed, and the effects on contingent negative variation (CNV) were studied. Mean CNV amplitude decreased in magnitude in the Fz as well as Cz areas; the decrease in Fz-CNV tended to be greater in those subjects whose sleep was most disturbed. The decrease in amplitude of CNV appears to be a nonspecific phenomenon that occurs after any kind of disturbed sleep. Contingent negative variation is composed of two or more components with different spatiotemporal distribution. Depending on the placement of electrodes, the effect that disturbed sleep has on CNV will or will not be observed. The decreases in CNV amplitude were noted in the Fz and Cz areas. Other than subjective discomforts, psychometric measurements did not change significantly. Our data indicate, from the topographical and constructional analysis of CNVs, the possible involvement of the frontal lobe function after disturbed sleep.

Adult↗

PubMed1990

Spatiotemporal properties of stereoacuity.

This study investigated the effects of spatial and temporal luminance variations on stereoacuity across three experiments. In Experiment 1, the effect of counterphase flicker on performance was examined at five spatial frequencies. Flicker impaired performance at a high spatial frequency, whereas it improved performance at a low spatial frequency. In Experiment 2, the effect of sustained vs. transient temporal modulation on performance was investigated at four spatial frequencies. Relative to sustained modulation, transient modulation impaired performance at high spatial frequencies, but it affected performance little at low spatial frequencies. In Experiment 3, the effect of exposure duration on performance was examined at three spatial frequencies. Decreasing duration impaired performance at a high spatial frequency, but it affected performance less at low spatial frequencies. These results show that spatial and temporal variables interact to govern stereoacuity performance; stereoacuity is good only when tested with high spatial- and low temporal-frequencies.

Depth Perception↗

PubMed1987

Conduction velocity variations minimize conduction time differences among retinal ganglion cell axons.

The visual system is able to accurately represent the spatiotemporal relations among the elements of a changing visual scene as the image moves across the retinal surface. This precise spatiotemporal mapping occurs despite great variability in retinal position and conduction velocity even among retinal ganglion cells of the same physiological class-a variability that would seem to reduce the precision with which spatiotemporal information can be transmitted to central visual areas. There was a strong negative relation between the intraretinal and extraretinal conduction time for axons of individual ganglion cells of the X-cell class. The effect of this relation was to produce a nearly constant total transmission time between the soma of a retinal X cell and its central target site. Thus, the variation in the conduction velocities of retinal ganglion cell axons may ensure that, regardless of the constraints imposed by retinal topography, a precise spatiotemporal central representation of the retinal image is maintained.

Action Potentials↗

PubMed1990

Sensitivity for interaural time and intensity difference of auditory midbrain neurons in the grassfrog.

The sensitivity for interaural time (ITD) and intensity (IID) difference was investigated for single units in the auditory midbrain of the grassfrog. A temporally structured stimulus was used which was presented by means of a closed sound system. At best frequency (BF) the majority of units was selective for ITD as indicated by an asymmetrically (73%) or symmetrically (7%) shaped ITD-rate histogram. About 20% appeared to be nonselective. Units with a symmetrical rate histogram had BFs well above 0.9 kHz, whereas for the other categories no relationship with BF was observed. Most units had a selectivity for ITD which was rather independent from frequency and absolute intensity level. In 62% of the units interaural time difference could be traded by interaural intensity difference. In most cases this so-called time-intensity trading could be explained by the intensity-latency characteristics of auditory nerve fibres. About 20% was sensitive to IID only and 5% to ITD only. A binaural model is proposed which is based on the intensity-rate and intensity-latency characteristics of auditory nerve fibres, the linear summation of excitatory and inhibitory post synaptic potentials in second order neurons, and spatiotemporal integration at the level of third order neurons. By variation of only a small number of parameters, namely strengths and time constants of the connectivities, the range of experimentally observed response patterns could be reproduced.

Acoustic Stimulation↗

PubMed1991

Spatiotemporal representation of moving luminance edges in human vision.

The edges of straight bars in a square-wave luminance grating appear undulating to an observer when the retinal image of this pattern is in motion. The amplitude of the perceived undulations increases linearly with retinal image speed with an average slope of 30 +/- 4 ms. The period of the motion-induced bulges is 2.5 +/- 0.5 degree and shows no consistent variation with the retinal image velocity of the pattern. The close quantitative agreement between the spatiotemporal extent of this effect and recent estimates of the spatiotemporal parameters of human motion-sensitive mechanisms suggests the existence of motion-sensitive cells in the central nervous system that have a fixed time constant but change the shape and size of their retinal support with retinal image velocity.

Humans↗

PubMed1983

Gradients of cellular maturation and synaptogenesis in the superior colliculus of the fetal rhesus monkey.

Light (LM) and electron microscopic (EM) qualitative and quantitative analyses were employed to determine the tempo and spatial gradients of synaptogenesis and cellular differentiation in the superficial superior colliculus (SC) of the rhesus monkey between embryonic (E) days E47 and E84. By E47, a majority of the neurons of the prospective superficial gray layer (SGS) have arrived at their final positions and contribute to a uniform band of small, darkly Nissl-stained neurons at the outer surface of the SC. By E54, cells in the middle of the rostral pole of the superficial SC become considerably larger, paler staining, and less densely packed than the more medially or laterally located cells. These regional differences, which extend posteriorly through about the middle of the SC at this age, are evident on both the LM and EM levels and were confirmed by a quantitative EM analysis of the cytodifferentiation and synaptogenesis in the SGS. Several overlapping EM probes made across the medial, middle, and lateral regions of the SGS at each of three coronal levels reveal consistently more developed neuropil and smaller amounts of extracellular space in the middle region than in the medial and lateral portions of the more anterior SC. Further, the densities of synapses, both in terms of synapses/micron2 of total cross-sectional area and synapses/micron2 of neuropil alone, are also higher in the middle than the peripheral regions. Most of the middle-peripheral differences found in the mid-E50s are still evident by the early E60s, but have disappeared by midgestation (E80s). The present results are interpreted to indicate that the middle region of the SGS at a given transverse level begins to mature significantly earlier than the medial or lateral areas. Since our previous 3H-thymidine analysis (Cooper and Rakic, '81a) failed to reveal significant regional variation in the time of neuron origin in the superficial SC, the observed spatiotemporal gradients of neuronal maturation in the primate SGS probably do not arise from underlying gradients of cellular proliferation.

Animals↗

PubMed1985

A qualitative dynamic analysis of reiterant speech production: phase portraits, kinematics, and dynamic modeling.

The departure point of the present paper is our effort to characterize and understand the spatiotemporal structure of articulatory patterns in speech. To do so, we removed segmental variation as much as possible while retaining the spoken act's stress and prosodic structure. Subjects produced two sentences from the "rainbow passage" using reiterant speech in which normal syllables were replaced by /ba/ or /ma/. This task was performed at two self-selected rates, conversational and fast. Infrared LEDs were placed on the jaw and lips and monitored using a modified SELSPOT optical tracking system. As expected, when pauses marking major syntactic boundaries were removed, a high degree of rhythmicity within rate was observed, characterized by well-defined periodicities and small coefficients of variation. When articulatory gestures were examined geometrically on the phase plane, the trajectories revealed a scaling relation between a gesture's peak velocity and displacement. Further quantitative analysis of articulator movement as a function of stress and speaking rate was indicative of a language-modulated dynamical system with linear stiffness and equilibrium (or rest) position as key control parameters. Preliminary modeling was consonant with this dynamical perspective which, importantly, does not require that time per se be a controlled variable.

Female↗

PubMed2025

Cilia in the brain display region-dependent oscillations of length and orientation.

In this study, we conducted high-throughput spatiotemporal analysis of primary cilia length and orientation across 22 mouse brain regions. We developed automated image analysis algorithms, which enabled us to examine over 10 million individual cilia, generating the largest spatiotemporal atlas of cilia. We found that cilia length and orientation display substantial variations across different brain regions and exhibit fluctuations over a 24-h period, with region-specific peaks during light-dark phases. Our analysis revealed unique orientation patterns of cilia, suggesting that cilia orientation within the brain is not random but follows specific patterns. Using BioCycle, we identified rhythmic fluctuations in cilia length across five brain regions: the nucleus accumbens core, somatosensory cortex, and the dorsomedial, ventromedial, and arcuate hypothalamic nuclei. Our findings present novel insights into the brain cilia dynamics, and highlight the need for further investigation into cilia's role in the brain's response to environmental changes and regulation of oscillatory physiological processes.

Animals↗

PubMed1983

Commentary: somatosensory evoked potentials and magnetic fields.

Evidence is offered for the requirement of more careful comparisons between the new event related magnetic fields of the brain (ERMFb) and their conventional counterparts the event related brain potentials (ERBP), in the somato-sensory (SEP) and auditory (AEP) modalities at least, because the existing ERBP literature contains a wealth of well-documented data on these crucial issues: (1) Contralateral and ipsilateral SEP; (2) the relevance of "background" intrinsic periodicity; and (3) the relevance of stimulus parameters, receptive fields, and subjective perceptual status to variations in the waveforms. The importance of the new 2nd derivative magnetic gradiometry for better spatiotemporal resolution of sources and for functional understanding of cerebral electrophysiology cannot be overestimated. So it may be equally important to ensure that existing, historical data from conventional scalp-conductance, systematically recorded and analyzed during the past twenty years, are not ignored at the inception of essential comparisons using complementary electromagnetic techniques.

Animals↗