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PubMed2006

Coral reef diversity refutes the neutral theory of biodiversity.

The global decline of coral reefs highlights the need to understand the mechanisms that regulate community structure and sustain biodiversity in these systems. The neutral theory, which assumes that individuals are demographically identical regardless of species, seeks to explain ubiquitous features of community structure and biodiversity patterns. Here we present a test of neutral-theory predictions with the use of an extensive species-level data set of Indo-Pacific coral communities. We show that coral assemblages differ markedly from neutral-model predictions for patterns of community similarity and the relative abundance of species. Within local communities, neutral models do not fit relative abundance distributions as well as the classical log-normal distribution. Relative abundances of species across local communities also differ markedly from neutral-theory predictions: coral communities exhibit community similarity values that are far more variable, and lower on average, than the neutral theory can produce. Empirical community similarities deviate from the neutral model in a direction opposite to that predicted in previous critiques of the neutral theory. Instead, our results support spatio-temporal environmental stochasticity as a major driver of diversity patterns on coral reefs.

Animals↗

PubMed2002

Alpha-sarcoglycan deficiency featuring exercise intolerance and myoglobinuria.

An 8-year-old boy was referred for recent onset of easy fatigue. He showed hyperCKemia and mild scapular winging. Muscle biopsy on the quadriceps muscle demonstrated slight fibre size variability. Dystrophin was normally distributed, carnitine palmitoyl transferase and glycolytic enzymes had normal activities. In the following years the patient developed exercise intolerance and myoglobinuria. Immunohistochemistry showed marked reduction of alpha-sarcoglycan, confirmed by Western blotting. Molecular analysis revealed compound heterozygosity with Arg284Cys and Glu137Lys substitutions, corresponding to nucleotide changes C850 T and G409 A in the gene. At present the patient, 20 years old, shows mild proximal weakness with prominent involvement of the paraspinal muscles, dorsal kyphosis and lumbar hyperlordosis. Exercise intolerance and myoglobinuria, already described in Becker muscular dystrophy, should be also considered among the possible presentations of sarcoglycan deficiencies.

Biopsy↗

PubMed1999

Performance of an enzyme-linked immunosorbent assay for the diagnosis of Brucella ovis infection in rams.

AIM: To describe the performance characteristics (sensitivity and specificity) of an enzyme-linked immunosorbent assay (ELISA) for the diagnosis of Brucella ovis infection in rams. METHODS: Sera from a negative (n = 2535) and a positive (n = 589) reference population were tested in an ELISA for anti-B. ovis antibodies and cut-off values calculated from the raw, log10-transformed and fitted data. Statistical methods were used to fit curves to the frequency distribution of the data and receiver-operated characteristics analysis used to optimise the cut-off values. RESULTS: Analysis of the frequency distribution of the positive ELISA values suggested a normal distribution of the data, whereas, in the case of the negative population, a Pearson type IV curve appeared to best fit the data. The cut-off values calculated as the mean plus 1.96 standard deviations (s.d.) from the raw, log-transformed and fitted ELISA data did not differ markedly. The differences were much greater at the mean plus 3.09 s.d. cut-off, with the cut-off value calculated from the log-transformed data giving a much better estimate of specificity. Optimisation (minimisation of classification error) of the cut-off calculated from the fitted curves suggested varying cut-off values, depending on the prevalence of B. ovis infection. DISCUSSION: Calculation of cut-off values from curves that were fitted from the observed data give more accurate estimations of the performance characteristics of an assay than traditional calculations from observed values. They also allow the calculation of optimal cut-off values taking into account the prevalence of B. ovis infection and give additional information about the performance of the assay at cut-off values varied according to the epidemiological situation.

Journal Article↗

PubMedDate not supplied

Evidence for a major gene effect in the distributions of digital ridge counts.

Previous attempts to isolate major gene effects in digital dermatoglyphics have been approached from two main directions. One has been concerned with analysing the components of total ridge count (TRC) distributions and examining various parameters of these distributions. The other has concentrated on the inheritance of various combinations of digital patterns. This study is primarily concerned with the shape of TRC and digital ridge count distributions. It suggests that a major gene effect may be as conspicuous in the distributions of digital counts as it is in TRC if these are viewed from the standpoint of global variation. The relationship between mean TRC, the standard deviation of TRC, skewness and kurtosis is examined and the results are compared with those obtained from a simple major locus model in which the overall distribution of TRC is composed of three overlapping normal distributions. As predicted by the model there is a negative correlation between mean TRC and its standard deviation, also a positive correlation with kurtosis. The expected relationship between mean TRC and skewness is non-linear, taking the form of an asymmetric U-shaped curve. There is evidence that the relationship between mean TRC and g1 in population samples covering a wide range of mean total ridge count follows this trend. The concordance between the predicted relationships and the observed frequency distributions is taken as evidence in favour of a single major locus hypothesis.

Dermatoglyphics↗

PubMedDate not supplied

The distribution of stature among Danish conscripts in 1852-56.

Stature measurements on large samples of unselected 22-year-old Danish males from the period 1852-56 are analysed. Data are given for 18 rural counties and the City of Copenhagen. The distribution of stature deviates significantly and systematically from Normality in all counties. A mixture of two Normal distributions with equal variances describes the empirical distribution of stature in the 18 rural counties and explains important aspects of the distribution of stature in the City of Copenhagen. This mixed structure of the population is accomplished by a factor reducing the mean stature of a fraction of the population by nearly 20 cm. The factor generating this mixed population is probably genetic and inbreeding may play a major part in raising the frequency of affected persons to the observed values, 0.2-2%. The mean stature of the majority of the population and the mixing proportion show significant geographical variation. The frequency of the small subpopulation is generally highest in the least-developed main province, Jutland, and lower on the islands, particularly in and around the City of Copenhagen. On the Zealand group of islands the mean stature of the majority of the population is highest in the most developed area, whereas the reverse occurs in Jutland.

Body Height↗

PubMed2006

Pre- and post-synaptic abnormalities associated with impaired neuromuscular transmission in a group of patients with 'limb-girdle myasthenia'.

The properties of neuromuscular junctions (NMJs) were studied in motor-point biopsy samples from eight patients with congenital myasthenic syndromes affecting primarily proximal limb muscles ['limb-girdle myasthenia' (LGM)]. All had moderate to severe weakness of the proximal muscles, without short-term clinical fatigability but with marked variation in strength over periods of weeks or months, with little or no facial weakness or ptosis and no ophthalmoplegia. Most had a characteristic gait and stance. All patients showed decrement of the compound muscle action potential (CMAP) on repetitive stimulation at 3 Hz, and increased jitter and blocking was detected by SFEMG, confirming the presence of impaired neuromuscular transmission. None of the patients had serum antibodies against acetylcholine receptors (AChRs). Two of the patients had similarly affected siblings. Intracellular recording from isolated nerve-muscle preparations revealed that the quantal content (the number of ACh quanta released per nerve impulse) was only approximately 50% of that in controls. However, the quantal size (amplitude of miniature end-plate currents) and the kinetic properties of synaptic potentials and currents were similar to control values. The area of synaptic contact and extent of post-synaptic folding were approximately 50% of control values. Thus, the quantal content per unit area of synaptic contact was normal. The number of AChRs per NMJ was also reduced to approximately 50% of normal, so the local AChR density was normal. Immunolabelling studies revealed qualitatively normal distributions and abundance of each of 14 proteins normally concentrated at the NMJ, including components of the basal lamina, post-synaptic membrane and post-synaptic cytoskeleton. DNA analysis failed to detect mutations in the genes encoding any of the following proteins: AChR subunits, rapsyn, ColQ, ChAT or muscle-specific kinase. Response of these patients to treatment was varied: few showed long-term improvement with pyridostigmine and some even deteriorated with treatments, while others had intolerable side-effects. Several patients showed improvement with 3,4-diaminopyridine, but this was generally only transient. Ephedrine was helpful in half of the patients. We conclude that impaired neuromuscular transmission in these LGM patients results from structural abnormalities of the NMJ, including reduced size and post-synaptic folding, rather from any abnormality in the immediate events of neuromuscular transmission.

Adolescent↗

PubMed1993

Estimation of protein coding density in a corpus of DNA sequence data.

A number of experimental methods have been reported for estimating the number of genes in a genome, or the closely related coding density of a genome, defined as the fraction of base pairs in codons. Recently, DNA sequence data representative of the genome as a whole have become available for several organisms, making the problem of estimating coding density amenable to sequence analytic methods. Estimates of coding density for a single genome vary widely, so that methods with characterized error bounds have become increasingly desirable. We present a method to estimate the protein coding density in a corpus of DNA sequence data, in which a 'coding statistic' is calculated for a large number of windows of the sequence under study, and the distribution of the statistic is decomposed into two normal distributions, assumed to be the distributions of the coding statistic in the coding and noncoding fractions of the sequence windows. The accuracy of the method is evaluated using known data and application is made to the yeast chromosome III sequence and to C. elegans cosmid sequences. It can also be applied to fragmentary data, for example a collection of short sequences determined in the course of STS mapping.

Animals↗

PubMed1998

The efficiency of CO2 elimination during high-frequency jet ventilation for laryngeal microsurgery.

UNLABELLED: For adequate and safe use of high-frequency jet ventilation (HFJV), reliable monitoring of the PCO2 status and course is necessary. Because of improved handling and performance, recently available transcutaneous PCO2 monitoring devices such as MicroGas 7650 (Kontron Instruments Medical Sensors, Basel, Switzerland) should enable more effective surveillance of CO2 elimination and, subsequently, better control of subglottic HFJV. Adult patients (n = 164) undergoing laryngeal microsurgery during total i.v. anesthesia were assessed. The resulting transcutaneous PCO2 values, as well as the necessary driving pressure settings, were analyzed to define the CO2 elimination capacity of each patient. Therefore, an individual CO2 elimination coefficient (ECCO2) was calculated. The frequency distribution of the obtained ECCO2 values showed a normal distribution with a median at 0.79 and a range between 0.30 and 2.17. A significant difference in the frequency of obstructive lung disease was found between two patient subpopulations separated by the 25th percentile at an ECCO2 value of 0.63. Other co-factors of CO2 elimination during HFJV were age, gender, and body weight, whereas height and ventilation duration were not involved. We conclude that the individual assessment of ECCO2 enables one to find adequate ventilator settings, resulting in lower airway pressure and less cooling and drying of the tracheobronchial mucosa. IMPLICATIONS: CO2 elimination during high-frequency jet ventilation can be assessed by calculating the CO2 elimination coefficient (ECCO2) of each patient from the required driving pressure and the resulting transcutaneous CO2 partial pressure. The frequency distribution of ECCO2 in a typical laryngological patient population was analyzed, and a value of 0.63 was found to be a characteristic limit between sufficient and difficult CO2 elimination. The individual assessment of ECCO2 enables one to find adequate ventilator settings, resulting in lower airway pressure and less cooling and drying of the tracheobronchial mucosa.

Adult↗

PubMed1993

Effect of hypothyroidism on rat peripheral nervous system.

The function and structure of the peripheral nervous system of Sprague-Dawley rats, 3 months after the induction of hypothyroidism by administration of N-propylthiouracil in drinking water, has been studied. The motor action potential amplitude of the caudal nerve showed a significant reduction (p < 0.001) when compared with an age-matched control group of animals. Computer-assisted morphometric analysis of sciatic nerves of hypothyroid rats showed normal distribution and density of myelinated fibers, and a normal axon/myelin ratio. Electron microscopy revealed only minor alterations in axons of myelinated fibers characterized by a dissolution of neurotubules. After two months of substitution therapy these effects were reversed. The present data suggest that early impairment of nerves induced by hypothyroidism is rare and could be related to metabolic alterations rather than to structural changes and is reversible with hormone treatment.

Action Potentials↗

PubMed1994

Statistical analysis of radioactive contamination levels in settlements of the Chernobyl middle zone.

A statistical analysis of the measurements of 137Cs activity density carried out in 1990-1991 in 30 settlements of the mesozone (and partially in the nearest zone) of the Chernobyl nuclear power plant is presented. It is shown that the mean activity density of radionuclides is close to 14 Bq cm-2 for the inspected settlements of Byelorussia which is significantly less than that for the inspected settlements of the nearest zone (48 Bq cm-2). The analysis shows that there is a near linear correlation between rms deviation of activity density and its mean value. It is also shown that the correlation radius of the data is comparable with the spatial step of the measurements and that the activity density distribution is reasonably described in terms of a normal distribution.

Accidents↗

PubMed2001

Dimensions of stabident intraosseous perforators and needles.

Problems can be encountered inserting intraosseous injection needles through perforation sites. This in vitro study examined the variability and size compatibility of Stabident intraosseous injection components. The diameters of 40 needles and perforators from a single Stabident kit were measured in triplicate with a toolmakers microscope. One-way ANOVA revealed that mean needle diameter (0.411 mm) was significantly narrower than mean perforator diameter (0.427 mm) (p < 0.001). A frequency distribution plot revealed that needle diameter followed a normal distribution, indicating tight quality control during manufacture. The diameter of perforators was haphazardly distributed, with a clustering of 15% at the lower limit of the size range. However on no occasion was the diameter of a perforator smaller than that of an injection needle. We conclude that components of the Stabident intraosseous anaesthetic system are size-compatible, but there is greater and more haphazard variability in the diameter of perforators than injection needles.

Analysis of Variance↗

PubMed2005

Monte Carlo calibration of avalanches described as Coulomb fluid flows.

The idea that snow avalanches might behave as granular flows, and thus be described as Coulomb fluid flows, came up very early in the scientific study of avalanches, but it is not until recently that field evidence has been provided that demonstrates the reliability of this idea. This paper aims to specify the bulk frictional behaviour of snow avalanches by seeking a universal friction law. Since the bulk friction coefficient cannot be measured directly in the field, the friction coefficient must be calibrated by adjusting the model outputs to closely match the recorded data. Field data are readily available but are of poor quality and accuracy. We used Bayesian inference techniques to specify the model uncertainty relative to data uncertainty and to robustly and efficiently solve the inverse problem. A sample of 173 events taken from seven paths in the French Alps was used. The first analysis showed that the friction coefficient behaved as a random variable with a smooth and bell-shaped empirical distribution function. Evidence was provided that the friction coefficient varied with the avalanche volume, but any attempt to adjust a one-to-one relationship relating friction to volume produced residual errors that could be as large as three times the maximum uncertainty of field data. A tentative universal friction law is proposed: the friction coefficient is a random variable, the distribution of which can be approximated by a normal distribution with a volume-dependent mean.

Complex Mixtures↗

PubMed2002

Viscosity and transient electric birefringence study of clay colloidal aggregation.

We study a synthetic clay suspension of laponite at different particle and NaCl concentrations by measuring stationary shear viscosity and transient electrically induced birefringence (TEB). On one hand the viscosity data are consistent with the particles being spheres and the particles being associated with large amount bound water. On the other hand the viscosity data are also consistent with the particles being asymmetric, consistent with single laponite platelets associated with a very few monolayers of water. We analyze the TEB data by employing two different models of aggregate size (effective hydrodynamic radius) distribution: (1) bidisperse model and (2) log-normal distributed model. Both models fit, in the same manner, fairly well to the experimental TEB data and they indicate that the suspension consists of polydisperse particles. The models also appear to confirm that the aggregates increase in size vs increasing ionic strength. The smallest particles at low salt concentrations seem to be monomers and oligomers.

Journal Article↗

PubMed2004

A simple method to assess severity of polymorphic light eruption.

BACKGROUND: The severity of polymorphic light eruption (PLE) is highly variable. The results of studies of the prevalence, pathogenesis, provocation and treatment of PLE may be highly dependent on the severity of disease in the patients studied. OBJECTIVES: To produce a simple, valid and reproducible method to assess the severity of PLE. PATIENTS AND METHODS: Eighty patients were asked about the PLE they had experienced during the preceding 12 months, using a standardized interview comprising 16 questions. The answer to each question received a score. A PLE Severity Index (PLESI) was formulated, consisting of 10 questions, with a possible total score of 2-100. The internal consistency of the PLESI (the extent to which the responses to different questions correlated with each other) was assessed by reliability analysis, using Cronbach's method. Twenty patients were re-interviewed 7-27 days later to assess the repeatability of the PLESI. The ease of provocation of PLE by exposure at 24-h intervals to solar-simulated radiation was assessed on a five-point scale in nine of the 80 subjects (the EOPSSR score). RESULTS: The value of Cronbach's alpha for the PLESI was 0.77. The distribution of the PLESI was consistent with a normal distribution, with a mean value of 52.7 and standard deviation of 19.4. It had a coefficient of repeatability of 20.1. The PLESI was positively correlated with EOPSSR (rs =0.69, P = 0.039) and the number of years since onset of PLE (rs = 0.25, P = 0.03). There was no association between the PLESI and the duration of persistence of the eruption after ceasing sun exposure (rs = 0.12, P = 0.30), the development of tolerance as summer progressed (rs = -0.14, P = 0.39), gender (P = 0.50) or skin type (P = 0.87). CONCLUSIONS: This study has (i) validated the concept that a single score can reflect disease severity in PLE by showing that the principal characteristics of the condition, including, for example, the extent of anatomical distribution and the ease of provocation of the eruption, correlate with each other; (ii) formulated the PLESI, which is a simple, valid and reproducible way of assessing disease severity; we suggest it could be used worldwide to determine the severity of PLE among patients enrolled in future PLE research; (iii) shown that the ease with which the eruption is provoked by solar-simulated radiation correlates with the severity of the condition; and (iv) shown that the duration of persistence of the eruption after sun exposure does not correlate with the severity of the condition.

Adolescent↗

PubMed2000

Treatment planning algorithm corrections accounting for random setup uncertainties in fractionated stereotactic radiotherapy.

A number of relocatable head fixation systems have become commercially available or developed in-house to perform fractionated stereotactic radiotherapy (SRT) treatment. The uncertainty usually quoted for the target repositioning in SRT is over 2 mm, more than twice that of stereotactic radiosurgery (SRS) systems. This setup uncertainty is usually accounted for at treatment planning by outlining extra target margins to form the planning target volume (PTV). It was, however, shown by Lo et al. [Int. J. Radiat. Oncol., Biol., Phys. 34, 1113-1119 (1996)] that these extra margins partly offset the radiobiological advantages of SRT. The present paper considers dose calculations in SRT and shows that the dose predictions could be made at least as accurate as in SRS with no extra margins required. It is shown that the dose distribution from SRT can be calculated using the same algorithms as in SRS, with the measured off-axis ratios (OARs) replaced by "effective" OARs. These are obtained by convolving the probability density distribution of the isocenter positions (assumed to be normal) and the original OARs. An additional output correction factor has also been introduced accounting for the isocenter dose reduction (2.4% for a 7 mm collimator) due to the OARs "blurring." Another correction factor accommodates for the reduced (by 1% for 6 MV beam) dose rate at the isocenter due to x-ray absorption in the relocatable mask. Mean dose profiles and the standard deviations of the dose (STD) were obtained through simulating SRT treatment by a combination of normally distributed isocenters. These dose distributions were compared with those calculated using the convolution approach. Agreement of the dose distributions was within 1%. Since standard deviation reduces with the number of fractions, N, as STD/square root(N), the planning predictions in fractionated stereotactic radiotherapy can be made more accurate than in SRS by increasing N and using "effective" OARs along with corrected dose output.

Algorithms↗

PubMed1993

Periodic synchronized bursting and intracellular calcium transients elicited by low magnesium in cultured cortical neurons.

1. In Mg(2+)-free external solution, rat cortical neurons in cultured networks entered a stable firing mode, consisting of regular bursts of action potentials superimposed on long-lasting depolarizations. The average separation between bursts varied from culture to culture, but was usually between 5 and 20 s. The distribution of burst intervals followed a Gaussian or normal distribution, with a standard deviation of typically 10% of the average burst period. 2. A gradually depolarizing pacemaker potential was never observed between bursts, but the threshold for action potentials during the quiescent phase was > or = 10 mV above the resting potential. No progressive change in conductance or excitability was observed during the quiescent period. Intracellular stimulation of action potentials did not reproduce the long-lasting depolarization. 3. Switching from current clamp to voltage clamp at the resting potential revealed large postsynaptic currents, mainly excitatory but with a small inhibitory component, at the same phase and frequency as the spike bursts, showing that periodic synaptic input is responsible for the burst-depolarizations. The current could be eliminated by local application of 2-amino-5-phosphonovaleric acid (APV) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) to the postsynaptic cell. In the presence of tetrodotoxin, irregular miniature excitatory postsynaptic currents were observed. 4. A fluorescent calcium indicator (fluo-3, 100 microM) was included in the whole-cell pipette solution, to allow simultaneous electrical and calcium measurements in the same cell. In current clamp, transient intracellular calcium increases were found, which were synchronized to the spike bursts. The Ca2+ rise lasted as long as the action potential burst, and was followed by an exponential decay considerably slower than that of the membrane potential. Calcium transients disappeared during voltage clamp at the resting potential, suggesting that calcium influx through voltage-dependent calcium channels greatly exceeds that through synaptic channels. 5. Multisite Ca2+ recording, after loading with fluo-3 acetoxymethyl (AM) ester, revealed that the onsets of burst-related calcium transients were synchronized in all active cells of each view-field, to within approximately 20 ms. Occasionally, secondary rhythms were observed in which only a subset of cells participated. The times to peak and the decay times of calcium transients varied among synchronized cells. 6. The pharmacology of the burst-related calcium transients was investigated by bath application of a variety of compounds.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1996

Synchronization of neurons during local field potential oscillations in sensorimotor cortex of awake monkeys.

1. The neural activity associated with 20- to 40-Hz oscillations in sensorimotor cortex of awake monkeys was investigated by recording action potentials of single and multiple units. At a given site, activity of many units became synchronized with local field potential (LFP) oscillations. Cycle-triggered histograms (CTHs) of unit spikes aligned on cycles of LFP oscillations indicated that about two thirds of the recorded units (n = 268) were entrained with LFP oscillations. On average, units had the highest probability of spiking 2.7 ms before peak LFP negativity, corresponding to a -27.6 degrees phase shift relative to the negative peak of the LFP. 2. The average relative modulation amplitude (RMA), defined as the ratio of amplitude of oscillatory component of CTH and the baseline multiplied by 100, was 45 +/- 27% (mean +/- SD). The RMAs of single units did not differ significantly from those of multiple units. 3. Phase shifts and RMAs did not vary systematically with the cortical depth of recorded units. 4. Autocorrelation histograms (ACHs) of entrained units exhibited clear 20- to 40-Hz periodicity if they were compiled with spikes that occurred during oscillatory episodes in LFPs. ACHs of spikes outside oscillatory episodes usually did not show periodicity. Global ACHs of all spikes typically showed weak or no evidence of periodic activity. 5. Cross-correlation histograms (CCHs) between pairs of units complied with all spikes, whether they occurred during or outside LFP oscillations, seldom revealed significant features (19 of 134 pairs or 14%). However, CCHs compiled with spikes that occurred during oscillatory episodes (OS-CCHs) had significant features in 67 of 134 pairs recorded ipsilaterally; in these 67 cases, units at both sites showed modulation in CTHs. 6. The latencies of the OS-CCH peaks (taking the medial unit as reference) were normally distributed about a mean of -0.5 +/- 13 ms. Normalized peak height of CCHs (peak/baseline x 100) was, on average, 14.3 +/- 11.2%. Peak latency and normalized peak amplitude did not change significantly with horizontal separation of recorded precentral pairs up to 14 mm. 7. Units in the left and right hemispheres could become synchronized during oscillations. Significant features in OS-CCH were detected in 22 of 42 pairs of units recorded bilaterally. The average peak latency was 0.2 +/- 8.0 ms and the average normalized peak amplitude was 10 +/- 8%. These parameters did not differ significantly from those for ipsilateral OS-CCHs. 8. Oscillations tended to affect both the temporal structure and net rate of unit firing. For each unit, the firing rate was clamped to a narrow range of frequencies during oscillatory episodes. The coefficient of variation (SD/mean) of firing rates was significantly reduced during oscillatory episodes compared with prior rates (P < 0.001, paired t-test). However, the overall mean firing rate of each unit during all oscillatory episodes did not differ from its average rate immediately before the episodes. Thus oscillatory episodes tended to clamp mean firing rates to the cells' average rates outside episodes. 9. The strength of synchronization between units during oscillatory episodes was unrelated to their involvement in the task. For pairs of precentral units recorded ipsilaterally, the probability of occurrence of significant features in the OS-CCH was slightly larger when both units of the pair were task related (33 of 56 pairs or 59%) than when only one unit was task related (20 of 39 pairs or 51%) or neither unit was task related (7 of 16 or 44%). However, these differences were not statistically significant. The magnitude of the correlation peak and the latency to peak were also not significantly different for the three cases. 10. These results suggest that units across wide regions can become transiently synchronized specifically during LFP oscillations, even if their spikes are uncorrelated during nonoscillatory periods.

Action Potentials↗

PubMed1996

Distribution of astigmatism in the adult population.

We have quantified statistically the astigmatic frequency distribution. Vectorial analysis was used, as it enables formal multivariate statistical techniques to be applied to astigmatic data, allowing the simultaneous inclusion of both modulus and axis in the analytical procedure. These methods were applied to population data for each of total, corneal, and residual astigmatism from a sample of 198 adults. Right and left eyes were analyzed separately. All the distributions were found to depart significantly from a normal distribution. All the distributions were significantly leptokurtic (p < 0.005), and the distributions of total right eye, corneal right eye, and residual left eye astigmatism were also found to be significantly skewed (p < 0.05). Significant mild correlations were found between total and corneal astigmatism (p < 0.05). These findings add to the database of knowledge of astigmatic refractive error and may be of interest to those investigating refractive-error development.

Adolescent↗