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Objectives: Clinical reasoning can be difficult to teach to pre-professional physiotherapy students due to their lack of clinical experience. It may be that tools such as clinical prediction rules (CPRs) could aid the process, but there has been little investigation into their use in physiotherapy clinical education. This study aimed to determine the perceptions and experiences of physiotherapy students regarding CPRs, and whether they are learning about CPRs on clinical placement., Design: Cross-sectional survey using a paper-based questionnaire., Participants: Final year pre-professional physiotherapy students (n=371, response rate 77%) from five universities across five states of Australia., Results: Sixty percent of respondents had not heard of CPRs, and a further 19% had not clinically used CPRs. Only 21% reported using CPRs, and of these nearly three-quarters were rarely, if ever, learning about CPRs in the clinical setting. However most of those who used CPRs (78%) believed CPRs assisted in the development of clinical reasoning skills and none (0%) was opposed to the teaching of CPRs to students. The CPRs most commonly recognised and used by students were those for determining the need for an X-ray following injuries to the ankle and foot (67%), and for identifying deep venous thrombosis (63%)., Conclusions: The large majority of students in this sample knew little, if anything, about CPRs and few had learned about, experienced or practiced them on clinical placement. However, students who were aware of CPRs found them helpful for their clinical reasoning and were in favour of learning more about them., (Copyright © 2016 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.)

Background: Research antibodies are used by thousands of scientists working in diverse disciplines, but it is common to hear concerns about antibody quality. This means that researchers need to carefully choose the antibodies they use to avoid wasting time and money. A well accepted way of selecting a research antibody is to identify one which has been used previously, where the associated data has been peer-reviewed and the results published., Description: CiteAb is a searchable database which ranks antibodies by the number of times they have been cited. This allows researchers to easily find antibodies that have been used in peer-reviewed publications and the accompanying citations are listed, so users can check the data contained within the publications. This makes CiteAb a useful resource for identifying antibodies for experiments and also for finding information to demonstrate antibody validation. The database currently contains 1,400,000 antibodies which are from 90 suppliers, including 87 commercial companies and 3 academic resources. Associated with these antibodies are 140,000 publications which provide 306,000 antibody citations. In addition to searching, users can also browse through the antibodies and add their own publications to the CiteAb database., Conclusions: CiteAb provides a new way for researchers to find research antibodies that have been used successfully in peer-reviewed publications. It aims to assist these researchers and will hopefully help promote progress in many areas of life science research.

Background: The relationship between health-related quality of life (HRQoL) in people with Parkinson's disease and their caregivers is little understood and any effects on caregiver strain remain unclear. This paper examines these relationships in an Australian sample., Methods: Using the generic EuroQol (EQ-5D) and disease-specific Parkinson's Disease Questionnaire-39 Item (PDQ-39), HRQoL was evaluated in a sample of 97 people with PD and their caregivers. Caregiver strain was assessed using the Modified Caregiver Strain Index. Associations were evaluated between: (i) caregiver and care-recipient HRQoL; (ii) caregiver HRQoL and caregiver strain, and; (iii) between caregiver strain and care-recipient HRQoL., Results: No statistically significant relationships were found between caregiver and care-recipient HRQoL, or between caregiver HRQoL and caregiver strain. Although this Australian sample of caregivers experienced relatively good HRQoL and moderately low strain, a significant correlation was found between HRQoL of people with PD and caregiver strain (rho 0.43, p < .001)., Conclusion: Poor HRQoL in people with PD is associated with higher strain in caregivers. Therapy interventions may target problems reported as most troublesome by people with PD, with potential to reduce strain on the caregiver.

Objective: To determine the efficacy of proton-pump inhibitor (PPI) therapy for chronic laryngo-pharyngitis treated with lifestyle modification., Study Design and Methods: Double-blind, randomized trial comparing two-month Rabeprazole (20 mg b.i.d.) to placebo control., Results: Compared to baseline, both PPI and control patients had significant improvement in total reflux symptoms (P = 0.002 and P = 0.03 respectively), with significant improvement in "laryngo-pharyngeal" but not "typical" reflux symptoms. No significant difference was noted for change in reflux symptoms between PPI-treated and control patients (P = 0.44). Significant global improvement was noted by 50% of control and 53% of PPI-treated patients (P = 1.0). No significant differences were noted within or between treatment groups for change in health status or videostrobolaryngoscopy grade. Lifestyle modification compliance correlated significantly with global improvement., Conclusion: Compared to baseline, lifestyle modification for 2 months significantly improved chronic laryngo-pharyngitis symptoms. When compared to control, treatment with a PPI failed to demonstrate significantly greater improvement in reflux symptoms, health status, or laryngeal appearance.

Our purpose was to identify and further characterize physiologic mechanisms relevant to autoresuscitation from hypoxic apnea in infants dying suddenly and unexpectedly. We studied cardiorespiratory recordings of 24 infants (age range, 0.8-21 months) who died suddenly while being monitored at home. These recordings were analyzed for features indicated by studies in animal models to be characteristic of hypoxic gasping, and of recovery from bradycardia and apnea associated with gasping (e.g., autoresuscitation). Findings in 5 infants diagnosed as having sudden infant death syndrome were compared with 6 non-SIDS infants whose deaths resulted from other conditions. Additionally, we studied 15 healthy infants during sleep, using home monitor and other respiratory recording techniques, in order to obtain comparison data. We found in recordings from 23 of 24 subjects that hypoxic gasps with characteristic features occurred immediately preceding death. A unique pattern of complex, closely spaced gasps ("double" or "triple" gasps) was present in many subjects. Evidence of partially successful autoresuscitation closely following one or more gasps occurred in 11 subjects, while another 4 had evidence of complete autoresuscitation with return of normal heart rate and resolution of apnea on one or more occasions. Significant differences between SIDS infants and those dying from other causes included increased occurrence of complex gasps and decreased occurrence of partial or complete autoresuscitation in the SIDS infants. The non-SIDS cases were different from the SIDS cases in that only one had "double" gasps (n = 7), while none had "triple" gasps, as compared with 4 out of 5 SIDS cases with these patterns (P < 0.05, chi-square). Also, in contrast with the SIDS cases, more of the cases with specific postmortem diagnoses had evidence of partial (5 out of 6 cases) or complete (1 out of 6 cases) autoresuscitation (P < 0.05, chi-square). We conclude that partial or complete autoresuscitation by gasping is not uncommon in moribund infants during the first year of life. Failure of autoresuscitation mechanisms other than failure to initiate gasping may be characteristic of infants dying of SIDS. Some SIDS infants appear to be different from infants dying with other diagnoses with respect to efficacy and characteristics of hypoxic gasping., (Copyright 2003 Wiley-Liss, Inc.)

Laryngeal cancer commonly causes loss of bodily functions, damage to the body image, and threat to life itself. Amputation of the voice as the result of laryngectomy alters the way patients, their families, and others perceive their bodily changes of function and often results in alterations in the activities and roles that they are able to carry out. Loss of body parts can have enormous physical and emotional impact on the patient. Likewise, the surgical creation of alternative openings and passages, which are readily seen during even the most casual contact, can have a profound effect on body image.

The geometric optics of an endoscope can be used to determine the absolute size of an object in an endoscopic field without knowing the actual distance from the object. This study explores the accuracy of a technique that estimates absolute object size from endoscopic images. Quantitative endoscopy involves calibrating a rigid endoscope to produce size estimates from 2 images taken with a known traveled distance between the images. The heights of 12 samples, ranging in size from 0.78 to 11.80 mm, were estimated with this calibrated endoscope. Backup distances of 5 mm and 10 mm were used for comparison. The mean percent error for all estimated measurements when compared with the actual object sizes was 1.12%. The mean errors for 5-mm and 10-mm backup distances were 0.76% and 1.65%, respectively. The mean errors for objects <2 mm and > or =2 mm were 0.94% and 1.18%, respectively. Quantitative endoscopy estimates endoscopic image size to within 5% of the actual object size. This method remains promising for quantitatively evaluating object size from endoscopic images. It does not require knowledge of the absolute distance of the endoscope from the object, rather, only the distance traveled by the endoscope between images.

This study aimed to evaluate the inter-rater and intra-rater reliability of a weight-bearing dorsiflexion (DF) lunge in 13 healthy subjects. Our raters with varying clinical experience tested all subjects in random order. Two of the raters repeated the measurements one week later. Two methods were used to assess the DF lunge: (i) the distance from the great toe to the wall and (ii) the angle between the tibial shaft and the vertical using an inclinometer. The average of three trials was used in data analysis. Intra-rater intraclass correlation coefficients (iccs) ranged from 0.97 to 0.98. Inter-rater ICC values were 0.97 (angle) and 0.99 (distance). results indicate excellent reliability for both methods of assessing a DF lunge.

To investigate the hypothesis that weight gain can influence periodic breathing in healthy infants, we prospectively studied, by nocturnal pneumogram technique, respiration and heart rate in 99 full-term infants during the first month of life. Eighty-eight infants had a repeat study at about 2 months of age. Pneumograms were analyzed visually for percent periodic breathing (%PB), and by computer for mean respiratory rate and mean heart rate. We found a median %PB of 0.9 initially and of 0.3 at about 2 months of age. The 95th percentile was 13.5 at 2 weeks and 7.3 at 2 months, higher than previously reported. Between the two ages tested, %PB was inversely correlated with weight gain (P < 0.001, < 0.03, respectively). Infants with greater weight gain had a greater fall in %PB (P < 0.03). We conclude that in the first 2 months of life, slow weight gain is associated with increased periodic breathing.

Several types of measurement were made of the negative afterimages formed by viewing chromatic and achromatic sine-wave conditioning gratings that were stabilized on the retina. We varied the spatial frequency, contrast, and duration of the conditioning stimulus and the interval between its offset and the afterimage measurement. Different methods of measuring afterimage contrast were also compared. We conclude that (1) an isoluminant chromatic stimulus creates an isoluminant chromatic afterimage; (2) afterimage contrast is linearly related to conditioning contrast; (3) chromatic and achromatic afterimages have similar low-pass spatial-frequency characteristics; (4) both types of afterimage build up and decay exponentially, with a (1/e) time constant of 4-8 s; (5) most important, both chromatic and achromatic afterimages raise the threshold for a chromatic flashed grating, but neither affects the threshold for an achromatic flashed grating; (6) we can explain these results by postulating that negative afterimages are subserved only by the sustained, or parvocellular, pathways.

Many children older than 12 months of age are now on home monitors. Home pneumograms performed on normal infants have established standards, and have been used to evaluate infants during their first year. However, no standards have been described for infants older than 12 months. We, therefore, recorded the standard pneumogram on 88 full-term healthy infants who were 12-18 months of age. We analyzed the recordings for average respiratory and heart rates, apnea (greater than or equal to 6 seconds) density, longest apnea, periodic breathing, and bradycardia for 12 hours. We compared the values in males vs. females and in infants 12-14.9 months vs. 15.0-18.0 months of age. Since there was no difference in any parameter measured in any group, we combined the values to determine the normal values for this population.

This paper reports an extended study of anomalous (enhanced) sensitivity to moving gratings in the range of 1-10 cycles per degree, at high temporal frequencies (greater than 20 Hz), i.e., in the high-frequency corner of the spatiotemporal threshold surface. The effect is very robust. All subjects (n = 5) show the effect with moving or flickering gratings and with or without stabilization of the retinal image. After eliminating various types of potential artifacts, the phenomenon was finally attributed to a form of transient destabilization associated with microsaccadic eye movements. In the unstabilized condition, microsaccades and voluntary saccades both interact with the grating motion to produce visible flashes. With image stabilization, the (1-msec) delay of the Purkinje-image eyetracker interacts with these saccades in a way that increases the visibility of the associated flashes. The form of the threshold data suggests that the size of the saccades may vary with the spatial period of the moving grating.

Lithium is known to affect several aspects of cellular regulation which may be related to ion channel function in epithelial cells. To determine whether the ion transport abnormality in cystic fibrosis (CF) is affected by lithium with resultant changes in clinical status, 36 CF patients, 12-37 years old, were enrolled in a 14 week, double-blind, placebo-controlled trial. Eighteen patients were randomly assigned to receive lithium carbonate for 10 weeks. At the end of therapy their average serum lithium concentration was 0.56 +/- 0.06 mmol (SEM) per liter. Their sweat chloride concentration fell from 92.1 +/- 4.8 mmol per liter to 87.4 +/- 4.0 mmol per liter after 10 weeks of therapy (P = 0.07) and rose to 94.4 +/- 3.5 mmol per liter 4 weeks after end of therapy (P less than 0.001 compared to results at end of therapy). Their forced vital capacity (FVC) fell from 72 +/- 5.3% of predicted to 66 +/- 5.1% of predicted after 4 weeks of therapy (P less than 0.01), and their forced expiratory volume in one second (FEV1) fell from 56 +/- 5.5% of predicted to 51 +/- 5.5% of predicted after 4 weeks of therapy (P less than 0.01). In a non-blind assessment, performed 19 weeks after the end of therapy, their FVC and FEV1 had risen and were not significantly different from baseline. Sweat chloride, FVC, and FEV1 remained unchanged in the placebo group throughout the period of study.(ABSTRACT TRUNCATED AT 250 WORDS)

Recordings of breathing movements and heart rate (pneumograms) were obtained prospectively in 89 preterm infants at 0-28 days of age to determine if those who develop apnea and/or bradycardia with cyanosis (Group 1) differ from those who do not (Group 2). The 148 pneumograms were blindly analyzed for periodic breathing, bradycardia, longest apnea, and quiet time. Pneumograms were compared between groups at weekly intervals during the first 4 weeks. Significant differences were found among infants who had pneumograms recorded during the 1st week of life. Although mean gestational age and mean postconceptional age at recording were similar, birthweight and weight at recording were significantly lower in Group 1 infants. Total time spent in periodic breathing and the longest episode of periodic breathing were significantly greater in Group 1 infants. Logistic regression analysis revealed significant independent relationships between birthweight and periodic breathing at less than or equal to 7 days of age and the occurrence of symptomatic apnea and/or bradycardia. It is concluded that preterm infants who develop apnea and/or bradycardia with cyanosis have a lower mean birthweight and mean weight at recording at less than or equal to 7 days of age than similar asymptomatic preterm infants. Periodic breathing at less than or equal to 7 days of age is associated with the occurrence of clinical symptoms of apnea and/or bradycardia. Normal pneumogram values for groups of 6-21 asymptomatic preterm infants are provided for the first 4 weeks of life.

We measure threshold for a vertical test grating superimposed on a fixed-contrast horizontal background grating of the same spatial and temporal frequency. The rate of change of this threshold with increasing contrast of the background grating is a measure of the contrast gain of the responding mechanism. Large slopes (high contrast gains) occur when spatial frequency is low and temporal frequency is high; small slopes (low contrast gains) occur when both spatial and temporal frequencies are low and when spatial frequency is high. This division of the spatiotemporal frequency domain into low- and high-gain regions is consistent with the transient/sustained dichotomy found in previous psychophysical studies. Furthermore, our results suggest that the mechanism responsible for detecting low spatial frequencies has a gain characteristic similar to that of cat retina Y cells and that the mechanism responsible for detecting high spatial frequencies has a gain characteristic similar to that of cat retina X cells, as found by Shapley and Victor [J. Physiol. (London) 285, 275-298 (1978)].

In the measurements of contrast thresholds for stationary, stabilized images, the choice of the psychophysical procedure may profoundly affect the results by constraining the time course of the stimulus presentation. With some procedures, the subject is unable to ignore transients; as a result, he necessarily responds to onset and offset transients rather than to the intended stimulus. Here we report significant effects of (a) the rapidly of onset and (b) the duration of the stimulus on thresholds for stabilized sinusoidal-grating patterns; these effects occur with both forced-choice and standard yes/no procedures. No value of either parameter (a) or (b) can eliminate such presentation effects when these procedures are used. However, we have devised a new, continuous-presentation procedure that yields results that do not depend on these parameters. Contrast thresholds for stabilized and for unstabilized stimuli measured by this procedure differ by 1 log unit or more, in good agreement with the results obtained by careful use of the method of adjustment.

Twenty-two full-term infants, aged 0 to 6 weeks, with a history of unexplained apnea and respiratory abnormalities on pneumogram recordings, were treated with theophylline (average dose 7.5 mg/kg/day and average serum level 11 micrograms/ml). Subsequent recordings showed a significant decrease in the amount of periodic breathing (14.3% vs 0.7%) and apnea 10 to 14.9 seconds (12.8 vs 1.0/100 min) when compared to the initial pneumogram. It is concluded that theophylline therapy in this group of infants will result in a reduction of apnea and periodic breathing.

The stabilized contrast-sensitivity function measured at a constant retinal velocity is tuned to a particular spatial frequency, which is inversely related to the velocity chosen. The Fourier transforms of these constant-velocity passbands have the same form as retinal receptive fields of various sizes. At low velocities, in the range of the natural drift motions of the eye, the stabilized contrast-sensitivity function matches the normal, unstablized result. At higher velocities (corresponding to motions of objects in the environment), this curve maintains the same shape but shifts toward lower spatial frequencies. The constant-velocity passband is displaced across the spatio-temporal frequency domain in a manner that is almost symmetric about the constant-velocity plane at v = 2 deg/s. Interpolating these diagonal profiles by a suitable analytic expression, we construct the spatio-temporal threshold surface for stabilized vision, and display its properties in terms of the usual frequency parameters; e.g., at low spatial frequencies, the temporal response becomes nearly independent of spatial frequency, while at low temporal frequencies, the spatial response becomes independent of temporal frequency.

This report examines the relationship between status origins and delinquency using an expanded range of status origin indicators together with both self-report and official measures of delinquency. Data were drawn from an ongoing investigation of adolescents in the Pacific Northwest. It was found that with few exceptions all four measures of status origins offer extremely low predictive utility vis-à-visdelinquent involvement. It is suggested that future efforts be directed at unraveling other more fruitful indicators of delinquency and, most especially, at examining the structure, process, and implications of differential status allocation within the educational arena.

When the image of a stationary, sinusoidal luminance grating is stabilized on the retina of a human subject, he becomes unable to detect this stimulus at contrasts that are readily visible in normal, unstabilized vision. At much higher contrasts, such stabilized gratings can still be seen over most of the normal range of spatial frequencies, although the threshold contrast may be increased by as much as 20 or 30 times. When the analogous experiment is performed with an isoluminance chromatic grating, however, there is no contrast that can restore the visibility of the stabilized grating; the threshold elevations for stabilized chromatic gratings are too great to measure. Saturated red/green gratings fade out and disappear at 100 percent contrast (even where this is 45 times the unstabilized threshold), and they do not reappear as long as stabilization is maintained. Without some kind of temporal variation of the proximal stimulus, the opponent-color pathways apparently do not respond to spatial patterns.

To test whether alveolar hypoventilation and an abnormal ventilatory response to inhaled carbon dioxide explains some episodes of sudden-infant-death syndrome, we assessed ventilatory control during quiet sleep in 12 normal infants and 11 infants who had required at least two resuscitations because of prolonged apnea (greater than 20 seconds) during sleep (aborted form of the syndrome). Infants with the aborted syndrome hypoventilated during quiet sleep (alveolar partial pressure of carbon dioxide, 38.9+/-3.5 mm Hg) as compared to normal infants (35.1+/-1.9, P less than 0.01). In addition, the ventilatory response to carbon dioxide breathing during quiet sleep was impaired (mean change in minute ventilation per change in partial pressure of carbon dioxide 22.1+/-8.9, as compared to 63.1+/-19.1 ml per kilogram per minute per millimeter of mercury in controls [p less than 0.001]). Three infants with the "aborted syndrome" subsequently died during sleep at home; autopsy, done in two, revealed no apparent cause of death. We conclude that infants who have had an episode consistent with sudden-infant-death syndrome have a defect in the regulation of alveolar ventilation.

It has been suggested that local variations of retinal sensitivity may be responsible for elevating the threshold in pattern-adaptation experiments of the Blakemore-Campbell type. Subjects are unable to scan high-contrast gratings uniformly enough to eliminate this possibility. To control this effect, we performed grating-adaptation experiments under stabilized-image conditions, while both adapting and test targets were moved at retinal velocities determined by the experimenter. By means of an afterimage technique, we also measured the strength of the retinal sensitivity mask that forms under these conditions. Varying the spatial frequency and velocity of the adapting stimulus, we inferred the spatial and temporal properties of the principal mechanism that contributes to the afterimage. We found that the Blakemore-Campbell effect persists at adapting velocities that are fast enough to rule out local variations of retinal sensitivity. More surprisingly, even the clearly visible afterimages that occur at a retinal velocity of 0.1 deg/s seem to have no effect on pattern adaptation. (Sensitivity masking can raise the adapted threshold, but only at adapting velocities slower than normal eye movements). By manipulating the image velocity, we were able to shift the spatial frequencies of some threshold-elevation curves, but these shifts were not great enough to suggest that velocity tuning plays important role in pattern adaptation.

The stabilized spatiotemporal threshold response surface can be modeled as the linear difference between the threshold response surfaces of two mechanisms, each of which is simply the product of a spatial and temporal frequency response curve. With no free parameters, the resulting model is shown to be a good fit to available data.

The exact relationship between cardiac arrhythmias and sudden infant death syndrome (SIDS) is uncertain. Several reports have implicated both ventricular and supraventricular arrhythmias in isolated cases, but there have been no studies of the incidence or type of arrhythmias that occur in populations at risk for SIDS. Of 1699 infants at high risk for SIDS, 60 (4%) were found to have a primary cardiac arrhythmia (i.e., not associated with disordered respiration or apnea). The incidence of atrial and ventricular premature beats, supraventricular tachycardia, and Wolff-Parkinson-White syndrome was similar to the incidence found in normal infants. Primary bradycardia (defined as a heart rate less than 60 for greater than 10 s not associated with abnormal respiration) was the most common arrhythmia, occurring with a frequency and severity not seen in normal infants. Thirty-two infants experienced periodic bradycardia. In 19 of these latter infants, there were symptoms associated with these bradyarrhythmias that necessitated treatment. Heart rates as low as 20 beats/min were recorded. One infant presented with an episode of ventricular fibrillation and on further evaluation was noted to have recurrent bradyarrhythmias. In no infant was there abnormal prolongation of the QT interval. Primary bradyarrhythmias are seen at an increased incidence in infants at high risk for SIDS and may play a causal role in this syndrome. Most symptomatic infants can be adequately controlled with sympathomimetic or parasympatholytic therapy. Other cardiac arrhythmias occur at a rate similar to that in normal infants and are therefore unlikely to play a major role in SIDS.

When stimulated in phase by a sinusoidally flickering, uniform field, the red and green cone systems tend to inhibit each other. This inhibition is minimized by (i) counterphase (luminance) patterns or (ii) red/green (chromaticity) flicker. However, when (i) and (ii) are combined, the usual flickering-pattern effect is reversed: instead of enhancing chromatic flicker, counterphase patterns tend to suppress it.

Twelve-hour nocturnal home recordings of respiration and heart rates were obtained during sleep in 32 infants with near-miss sudden infant death syndrome (SIDS) and in 32 control infants, and the recordings were analyzed for periodic breathing. An episode of periodic breathing was defined as three or more apneic pauses of three or more seconds. The duration of respirations interrupting the pauses was 20 seconds or less. Analysis revealed a statistically significant difference (P less than .001) between the two groups, using criteria of percent of periodic breathing episodes, number of periodic breathing episodes/100 min of recorded sleep time, average duration of all episodes, and duration of the longest episode of periodic breathing. It is concluded that periodic breathing is present in excessive amounts during sleep in infants with near-miss sudden infant death syndrome.

By compensating for retinal inhomogeneity and using the opponent-color characteristics of retinal receptive fields, some of the problems associated with previous methods of inferring local spatial-processing properties from sine-wave contrast-sensitivity measurements can be eliminated. Forced-choice contrast detection thresholds were obtained for circular frequency-modulated patterns, over a wide range of spatial and temporal frequencies, with three subjects. Eye-movement artifacts were minimized by image stabilization. The luminance contrast sensitivity (L) for a given isochromatic stimulus and the chromatic contrast sensitivity (C) for the corresponding isoluminance stimulus were measured in rapid succession, under identical conditions, using red and green components with accurately known spectral distributions. Receptive-field center (E) and surround (I) frequency functions were then calculated from the L and C data by solving two linear equations in two unknowns, with coefficients given by the spectral characteristics of the stimuli and the long-wave and middle-wave cone pigments. The results depend on the small differences of large numbers inherent in opponent-color responses, so they are somewhat noisy, but the forms of these (E-I) spatial profiles are similar to those obtained by other methods.

We have tested the hypothesis that autonomic instability, reflected in increased variability of heart rate and respiratory frequency, characterized high risk babies who died of sudden infant death syndrome. Using computer-based methods, we compared the power spectra of instantaneous heart rate and respiration on coded tape recordings from seven asymptomatic siblings and 10 babies with symptomatic apnea who died of sudden infant death syndrome to 34 age- and sex-matched controls. We confirmed our previous observation of increased respiratory bandwidth, an index of variability in respiratory frequency (p = 0.009) but failed to confirm our finding of increased low frequency fluctuations in heart rate (p = 0.18). In addition, we found an increase in mean respiratory frequency during quiet breathing (p = 0.001) and a significant relationship between respiratory bandwidth and mean respiratory frequency (r = 0.604, p = 0.0002). These variables along with those from a previous analysis of the same data base yield a discriminant function with 82% sensitivity and 100% specificity. These results confirm previous suggestions that high risk babies who die of sudden infant death syndrome exhibit autonomic instability.

Lingual vibrotactile thresholds (LVTs) were determined at 125, 250, and 500 Hz for 30 children with defective articulation and 30 children with normal articulation. Secondly, attempts to predict the phonemic and distinctive feature errors from LVTs for defective articulating children is presented. Children with normal articulation show significantly lower (better) LVTs at each frequency than do children with defective articulation. Significant relationships were not found between LVTs and phonemic scores or distinctive feature errors.

Over a range of high temporal and low spatial frequencies, counterphase flickering gratings evoke the so-called frequency-doubling illusion, in which the apparent brightness of the grating varies at twice its real spatial frequency. The form of the nonlinearity that causes this second-harmonic distortion of the visual response was determined by a cancellation technique. The harmonic distortion can be measured as a function of amplitude (or contrast) by adding to the flickering grating a real, nonflickering, double-frequency component with the amplitude and phase required to cancel the illusory second harmonic. Harmonic distortion curves obtained in this way imply that the nonlinearity is of the form /s/p, where s is the stimulus pattern (without its dc component) and p is close to 0.6. If p = 1, or if the absolute value is not taken, this expression predicts distortion curves that differ significantly from the experimental results. Hence neither rectification nor compression alone is sufficient to account for the second-harmonic distortion; both are required.

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.

Victims of sudden infant death syndrome (SIDS) have occasionally been reported to have had prolonged apnea or an increased frequency of short apnea prior to their deaths. To examine the extent of these abnormalities, we compared pneumograms obtained in 17 infants who subsequently died of SIDS (10 with history of apnea) with those of 34 age- and sex-matched controls. The recordings were analyzed by a computer program that avoided observer bias. SIDS infants had significantly greater mean heart rate (P less than 0.05) and periodic breathing during quiet time (P less than 0.003) than control infants had. The apnea in SIDS infants tended to be more periodic than in control infants (P less than 0.002). In addition, the incidence of bradycardia was greater in SIDS (three infants) than in controls (none) (P less than 0.03). These differences suggest a disturbance of autonomic function prior to death in some victims of SIDS.