The development of visual attention in infancy

Over the past decade, the study of attention in infancy has seen dramatic progress. This review delineates four attentional functions (alertness, spatial orienting, attention to object features, and endogenous attention) that are relevant to infancy and uses these functions as a framework for summarizing the developmental course of attention in infancy. Rudimentary forms of various attentional functions are present at birth, but each of the functions exhibits different and apparently dissociable periods of postnatal change during the first years of life. The role of attention in development should therefore be considered in the context of interaction among different systems at different levels of maturity during the first years of life.

Individual and developmental differences in disengagement of fixation in early infancy

The current study investigated whether individual and developmental differences in look duration are correlated with the latency for infants to disengage fixation from a visual stimulus. Ninety-four infants (52 3-month-olds, 42 4-month-olds) were tested in a procedure that measured ocular reaction time to shift fixation from a central target to a peripheral target under conditions in which the central-target either remained present ("competition" condition) or was removed from the display ("noncompetition" condition). Look duration was correlated with disengagement latency; longer-looking infants were slower than shorter-looking infants to shift fixation to the peripheral target on competition trials, but not noncompetition trials. Results were similar for 3- and 4-month-olds, although 3-month-olds showed slower latencies on all trials. Furthermore, long-looking infants were not consistently slower, but rather showed greater variability in their response latencies under conditions that required disengagement of fixation. The results support the position that developmental and individual differences in look duration are linked to the development of the neural attentional systems that control the ability to disengage, or inhibit, visual fixation.

A model of electrical excitation of the mammalian auditory-nerve neuron

A model of the mammalian auditory-nerve neuron has been developed based on the classical work of Frankenhauser and Huxley [(1964) J. Physiol. 171, 302-315], modified by McNeal [(1976) IEEE Trans. Biomed. Eng. BME-23, 329-336], and Reilly et al. [(1985) IEEE Trans. Biomed. Eng. BME-32, 1001-1011], and fine tuned to represent physiological data obtained from single auditory-nerve fiber experiments in squirrel monkeys. The model is capable of reproducing neural action potential waveforms due to electrical stimulation, and can reliably predict action potential thresholds and strength-duration curves. This paper explains the derivation of the mathematical model and the effects of varying certain independent parameters including fiber diameter, length of the nodes of Ranvier, internodal length, and myelin thickness. The model parameters were selected according to the anatomical findings of Liberman and Oliver [(1984) J. Comp. Neurol. 223, 163-176], and Liberman (Pers. Commun.). The length of the unmyelinated termination of the auditory-nerve that survives after aminoglycoside damage to the inner ear has not been experimentally determined. Therefore, it was investigated as an independent variable in the model. An unmyelinated terminal length of 10.0 micron was found to most accurately describe the experimental neural strength-duration curves obtained from aminoglycoside-deafened squirrel monkeys. The parameter that had the next most significant effect on the model was fiber diameter which affects all conduction pathways, across the membrane and through the fiber. Finally the results of the model are compared with behavioral data obtained from patients and monkeys implanted with cochlear prostheses. In the companion paper [(1987) Hear. Res. 31, 267-286] predictions of the model are quantitatively compared with single-neuron data from squirrel monkeys.

Heart rate-defined phases of attention, look duration, and infant performance in the paired-comparison paradigm

Four-month-old infants (N = 68) were tested in a paired-comparison familiarization-novelty recognition task in which the length of choice trials was systematically manipulated. Peak look duration during pretest and familiarization periods significantly predicted a dichotomous measure of recognition performance, but recognition was unaffected by choice-trial length. Heart rate (HR) was simultaneously assessed during the task, and the amount of time infants spent in various HR-defined phases of attention was assessed. Longer durations of looking during pretest and familiarization were significantly associated with more time spent in both sustained attention (SA) and attention termination (AT). Of these two variables, only individual differences in AT accounted for significant variance in recognition memory performance. A final analysis addressed the possibility that individual differences in AT mediated the relation between look duration and recognition performance. These findings provide support for the hypothesis that individual differences in the disengagement of attention underlie the relation between look duration and cognitive performance in early to midinfancy.

Serotonergic sprouting in primate MTP-induced hemiparkinsonism

Immunocytochemistry to serotonin, dopamine beta hydroxylase (DBH), and tyrosine hydroxylase (TH) was studied in the brains of 2 cebus monkeys that had developed permanent hemiparkinsonism after intracarotid injection of 1.2 mg N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and were sacrificed after 10-12 months. A pronounced depletion of TH-immunoreactive neurons was found in the substantia nigra, caudate nucleus, and putamen, ipsilaterally to the injected side. In these dopamine-denervated structures, the number of serotonergic fibers was increased in the ipsilateral compared with the contralateral side, or with an untreated control monkey. Serotonergic neurons in the brainstem appeared to be unaffected. Topography and number of DBH-positive fibers in the control and the MPTP-injected sides were comparable.

Nodal size of metastatic squamous cell carcinoma of the neck

The preoperative use of computed tomographic (CT) scanning continues to be the best diagnostic method for preoperative detection of metastatic neck disease. Current accepted criteria for CT diagnosis of nodal disease are not uniform, although nodal size, nodal grouping, and central necrosis correlate strongly with malignancy. To assess the relationship of nodal size and malignancy, a multicenter study was designed to evaluate the nodes from 100 neck dissections. Sixty-nine positive neck dissections were analyzed, and every node was measured. The relationship of central necrosis was also compared with node size. Our results showed that CT scanning continues to provide a reliable picture of the histologic status of lymph nodes. Using the criterion of central necrosis or node size larger than 1 cm, only 7% of necks had nodal disease that would have been missed by CT interpretation. This study supports the continued use of preoperative CT evaluation for metastatic neck disease.

Effects of docosahexaenoic acid supplementation during pregnancy on fetal heart rate and variability: a randomized clinical trial

DHA (22:6n-3) supplementation during infancy has been associated with lower heart rate (HR) and improved neurobehavioral outcomes. We hypothesized that maternal DHA supplementation would improve fetal cardiac autonomic control and newborn neurobehavior. Pregnant women were randomized to 600 mg/day of DHA or placebo oil capsules at 14.4 (+/-4) weeks gestation. Fetal HR and HRV were calculated from magnetocardiograms (MCGs) at 24, 32 and 36 weeks gestational age (GA). Newborn neurobehavior was assessed using the Neonatal Behavioral Assessment Scale (NBAS). Post-partum maternal and infant red blood cell (RBC) DHA was significantly higher in the supplemented group as were metrics of fetal HRV and newborn neurobehavior in the autonomic and motor clusters. Higher HRV is associated with more responsive and flexible autonomic nervous system (ANS). Coupled with findings of improved autonomic and motor behavior, these data suggest that maternal DHA supplementation during pregnancy may impart an adaptive advantage to the fetus.

Preservation of amplitude modulation coding in the presence of background noise by chinchilla auditory-nerve fibers

Sound envelope temporal fluctuations are important for effective processing of biologically relevant acoustic information including speech, animal vocalizations, sound-source location, and pitch. Amplitude modulation (AM) of sound envelopes can be encoded in quiet with high fidelity by many auditory neurons including those of the auditory nerve (AN) and cochlear nucleus. From both neurophysiological and clinical perspectives, it is critical to understand the effects of background masking noise on the processing of AM. To further this goal, single-unit recordings were made from AN fibers in anesthetized chinchillas. Units were classified according to spontaneous firing rate (SR) and threshold. Best frequency (BF) pure-tone bursts and AM (10-500 Hz) tone bursts were employed as stimuli at several sound levels, both in quiet and in the presence of a continuous wideband noise. It was found that (1) in quiet, low SR AN fibers show the strongest AM coding, followed in order by medium SR and high SR fibers, respectively. (2) AN units of all three classes generally preserve their AM coding even in the presence of loud (0 or +6 dB S/N) background noise and at high sound levels (over 75 dB SPL). (3) This preservation is usually achieved by lowering the average firing rate proportionately to decreases in the synchronous (fundamental frequency) response. (4) For a few AN fibers, the AM coding increases or is reduced in the presence of the background noise. These findings suggest that AN preservation of AM coding in the presence of a continuous masking noise results from shifts in the operating ranges and firing rates of AN fibers resulting from cochlear nonlinearities and adaptive mechanisms.

Infant visual attention in the paired-comparison paradigm: test-retest and attention-performance relations

The visual behavior of infants in the paired-comparison paradigm was assessed with multiple discrimination tasks week-to-week at 4 and 7 months and longitudinally from 4 to 7 months. Results indicated that although task-to-task reliability was extremely variable and typically low, most measures of infants' attention averaged across multiple tasks were reliable from 1 week to the next as well as relatively stable over the longer longitudinal period. Across all groups, infants who had shorter fixations (i.e., more fixations per fixed-exposure period) during the familiarization phase showed higher novelty preferences. While infants' shift rate during test phases was a reliable individual characteristic at 7 months, it was not at 4 months; rather, data suggested that the difficulty of the stimulus discrimination may be related to young infants' shift rate.

Extracorporeal lung perfusion and ventilation to improve donor lung function and increase the number of organs available for transplantation

INTRODUCTION

Ex vivo lung perfusion (EVLP) has been validated as a valuable technique to increase the pool of organs available for lung transplantation.

MATERIAL AND METHODS

After a preclinical experience, we obtained permission from the Ethics Committee of our institution to transplant lungs after EVLP reconditioning. ABO compatibility, size match, and donor arterial oxygen pressure (PaO(2))/fraction of inspired oxygen (FiO(2)) ≤ 300 mm Hg were considered to be inclusion criteria, whereas the presence of chest trauma and lung contusion, evidence of gastric content aspiration, pneumonia, sepsis, or systemic disease were exclusion criteria. We only considered subjects on an extra corporeal membrane oxygenation (ECMO) bridge to transplantation with rapid functional deterioration. Using Steen solution with packed red blood cells oxygenated with 21% O(2), 5% to 7% CO(2) was delivered, targeted with a blood flow of approximately 40% predicted cardiac output. Once normothermic, the lungs were ventilated with a tidal volume of 7 mL/kg a PEEP of 5 cmH(2)O and a respiratory rate of 7 bpm. Lungs were considered to be suitable for transplantation if well oxygenated [P(v-a) O(2) > 350 mm Hg on FiO(2) 100%], in the absence of deterioration of pulmonary vascular resistance and lung mechanics over the perfusion time.

RESULTS

From March to September 2011, six lung transplantations were performed, including two with EVLP. The functional outcomes were similar between groups: at T72 posttransplantation, the median PaO(2)/FiO(2) were 306 mm Hg (range, 282 to 331 mm Hg) and 323 mm Hg (range, 270 to 396 mm Hg) (P = 1, EVLP versus conventional). Intensive care unit ICU and hospital length of stay were similar (P = .533 and P = .663, respectively) with no mortality at 60 days in both groups. EVLP donors were older (49 ± 6 y versus 21 ± 7 y, P < .05), less well oxygenated (184 ± 6 mm Hg versus 570 ± 30, P < .05), displaying higher Oto scores (9.5 ± 0.7 versus 1.7 ± 1.5, P < .05).

CONCLUSIONS

The first 6 months of the EVLP program allowed us to increase the number of organs available for transplantation with short-term outcomes comparable to conventional transplantations.

Recent advances in infant cognition: implications for long-chain polyunsaturated fatty acid supplementation studies

The assessment of cognitive function in early life has recently become an issue for consideration in long-chain polyunsaturated fatty acid (LC-PUFA) supplementation studies. This article reviews the various means by which such assessment has been done in past LC-PUFA supplementation studies and provides some background on recent advances in the measurement of infant cognition that may need to be considered when planning or designing future supplementation studies. These include (i) consideration of the specificity of LC-PUFA effects on cognition, (ii) inclusion of multiple tasks or levels of measurement as outcome measures, and (iii) a stronger emphasis on developmental processes in the design of such studies.

Stimulus context and infant orientation discrimination

In three experiments, the effect of additional "contextual" elements on the discrimination of the orientation of linear and curvilinear segments was investigated with 4-month-old infants. In Experiment 1, paired visual matrices (one which contained some irregularity in orientation of internal elements, vs one which contained no irregularities) were presented. Infants detected irregular matrices significantly better than chance, but such detection was not aided by contextual elements. Discrimination of orientation in Experiment 2 was assessed with a paired-comparison familiarization-novelty paradigm. It was found that the addition of elements here significantly aided discrimination of linear segment orientation, but not curvilinear segment orientation. Experiment 3 investigated why this effect was not found for curvilinear segments; after equating the curvilinear stimuli to linear ones used in Experiment 2 with respect to the closedness of figure, discrimination of curvilinear orientation was observed.

Predicting the effect of maternal docosahexaenoic acid (DHA) supplementation to reduce early preterm birth in Australia and the United States using results of within country randomized controlled trials

The DHA to Optimize Mother Infant Outcome (DOMInO) and Kansas DHA Outcomes Study (KUDOS) were randomized controlled trials that supplemented mothers with 800 and 600mg DHA/day, respectively, or a placebo during pregnancy. DOMInO was conducted in Australia and KUDOS in the United States. Both trials found an unanticipated and statistically significant reduction in early preterm birth (ePTB; i.e., birth before 34 weeks gestation). However, in each trial, the number of ePTBs were small. We used a novel Bayesian approach to estimate statistically derived low, moderate or high risk for ePTB, and to test for differences between the DHA and placebo groups. In both trials, the model predicted DHA would significantly reduce the expected proportion of deliveries in the high risk group under the trial conditions of the parent studies. Among the next 300,000 births in Australia we estimated that 1112 ePTB (95% credible interval 51-2189) could be avoided by providing DHA. And in the USA we estimated that 106,030 ePTB (95% credible interval 6400 to 175,700) could be avoided with DHA.

Form categorization in 10-month-olds

In five experiments, 10-month-olds were habituated to exemplars of a form category and tested for categorization in paired-comparison trials involving in-category versus out-of-category stimuli. Across these experiments, color was systematically manipulated during habituation and/or test trials. Infants categorized form when color was either held constant or varied during habituation, but failed to categorize form when exposed to color-constant stimuli during habituation and tested for categorization with novel-color form exemplars. Two subsequent experiments traced this failure to the narrow experience of exposure to color-constant exemplars during habituation. These results suggest that (a) infants' internal representation for a category will not include a stimulus dimension not varied in the exemplars from which the category was derived, but (b) if variation in that dimension is experienced, exemplars constructed of novel instances of that dimension will still be regarded as belonging to the category.

Long- and short-looking infants' recognition of symmetrical and asymmetrical forms

Adults process symmetrical visual forms more rapidly than asymmetrical visual forms, presumably because symmetrical forms are amenable to a global visual encoding strategy. Individual differences in look duration during infancy have been hypothesized to covary with different modes of visual intake and encoding, with longer look durations reflecting encoding based on prolonged inspection of local visual properties, and briefer look durations reflecting encoding based on more of a global, or global-to-local processing sequence. This hypothesis predicts that short-looking infants would process symmetrical stimuli faster than asymmetrical stimuli, but that long-looking infants would not. Three experiments are described here in which this prediction is tested. Results were in general accord with the prediction, and provide further support for the hypothesis that individual differences in look duration may reflect different modes of visual encoding or inspection.

Sensitization during visual habituation sequences: procedural effects and individual differences

Although individual differences in visual habituation have long been interpreted in terms of processes derived from comparator theory, research over the last decade has suggested that arousal or arousability as manifest in sensitization may contribute to infants' attentional profiles, and thus, to individual differences in those profiles. We explored this possibility by habituating 4-month-old infants to 4 x 4, 10 x 10, or 20 x 20 checkerboards in a fixed-trial paradigm. The first specific aim was to examine the attentional characteristics of infants with habituation patterns showing sensitization versus those that did not. The second specific aim was to determine whether patterns of attention suggestive of sensitization effects reported in past research might be attributable to the use of illuminated interstimulus intervals (ISIs). Trends were observed for sensitization to occur more frequently with more complex than with less complex checkerboards. Infants who showed looking patterns characteristic of sensitization looked longer and did not habituate as readily as infants who did not show sensitization. Finally, different ISIs did not engender different levels of sensitization, but dark ISIs significantly increased infants' looking times to stimuli during trials.

Docosahexaenoic acid (DHA) supplementation in pregnancy differentially modulates arachidonic acid and DHA status across FADS genotypes in pregnancy

Some FADS alleles are associated with lower DHA and ARA status assessed by the relative amount of arachidonic acid (ARA) and docosahexaenoic acid (DHA) in plasma and red blood cell (RBC) phospholipids (PL). We determined two FADS single nucleotide polymorphisms (SNPs) in a cohort of pregnant women and examined the relationship of FADS1rs174533 and FADS2rs174575 to DHA and ARA status before and after supplementation with 600mg per day of DHA. The 205 pregnant women studied were randomly assigned to placebo (mixed soy and corn oil) (n=96) or 600mg algal DHA (n=109) in 3 capsules per day for the last two trimesters of pregnancy. Women homozygous for the minor allele of FADS1rs174533 (but not FADS2rs174575) had lower DHA and ARA status at baseline. At delivery, minor allele homozygotes of FADS1rs174533 in the placebo group had lower RBC-DHA compared to major-allele carriers (P=0.031), while in the DHA-supplemented group, all genotypes had higher DHA status compared to baseline (P=0.001) and status did not differ by genotype (P=0.941). Surprisingly, DHA but not the placebo decreased ARA status of minor allele homozygotes of both FADS SNPs but not major allele homozygotes at delivery. Any physiological effects of changing the DHA to ARA ratio by increasing DHA intake appears to be greater in minor allele homozygotes of some FADS SNPs.

Discrimination learning during the first year: Stimulus and positional cues

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues.

Mass hearing screening in kindergarten students

OBJECTIVE

To determine the types of hearing losses identified by mass hearing screenings in the public school system.

DESIGN

Prospective observational.

PARTICIPANTS

Students enrolled in kindergarten in the public school system.

SETTING

Major metropolitan area.

MAIN OUTCOME MEASURES

(1) hearing screening tests performed by speech pathologists using an audiometer in a quiet room; (2) formal audiologic testing including pure tone audiometry, tympanograms, speech discrimination, and acoustic impedance testing in a sound proof booth.

RESULTS

140 students failed hearing screening on two separate occasions; 91(65%) underwent formal audiologic testing at Milwaukee Public School, 43% demonstrated conductive hearing losses, 14% demonstrated sensorineural losses and 43% demonstrated normal hearing.

CONCLUSION

Mass hearing screening in the school system (1) is useful for detecting transient conductive hearing losses, (2) detects a significant number of sensorineural hearing losses and (3) has a very poor follow-through by the families of those students identified with hearing loss through the screening program.

Docosahexaenoic acid supplementation (DHA) and the return on investment for pregnancy outcomes

The Kansas University DHA Outcomes Study (KUDOS) found a significant reduction in early preterm births with a supplement of 600mg DHA per day compared to placebo. The objective of this analysis was to determine if hospital costs differed between groups. We applied a post-hoc cost analysis of the delivery hospitalization and all hospitalizations in the following year to 197 mother-infant dyads who delivered at Kansas University Hospital. Hospital cost saving of DHA supplementation amounted to $1678 per infant. Even after adjusting for the estimated cost of providing 600mg/d DHA for 26 weeks ($166.48) and a slightly higher maternal care cost ($26) in the DHA group, the net saving per dyad was $1484. Extrapolating this to the nearly 4 million US deliveries per year suggests universal supplementation with 600mg/d during the last 2 trimesters of pregnancy could save the US health care system up to USD 6 billion.

Spectral complexity and infant attention

In two experiments, infants selectively attended to auditory stimuli that presented an increasingly complex spectral structure. Using 2- and 4-month-olds as subjects, the first study demonstrated this selectivity in comparison to the rate of acoustic change. The second study demonstrated the increased attention of 4-month-olds in response to an increasingly complex structure. Results are discussed with respect to the neural activity produced by these stimuli along the auditory pathway, and an analogy to the literature on visual attention is drawn.

Streptococcal fasciitis with toxic shock syndrome in the pediatric patient

Necrotizing fasciitis (NF) is a distinctive soft tissue infection usually caused by Group A beta-hemolytic streptococcus, often seen in association with varicella in the previously healthy child. Its fulminant course is associated with great morbidity and high case-fatality rates, especially when it occurs in conjunction with streptococcal toxic shock syndrome. It differs from simple cellulitis in clinical presentation, appearance on examination, and need for urgent surgical intervention. The patient is irritable and complains of severe pain in the involved site, which is usually the extremity. On examination, exquisite pain on palpation of the involved site is confirmed, which is out of proportion to the cutaneous findings. Shock, multiorgran failure, and death will ensue if the diagnosis is not promptly recognized. The five keys to management include fluid management, aggressive debridement of necrotic tissues, anticipation and management of multisystem organ failure, appropriate parenteral antimicrobial therapy using penicillin and clindamycin, and use of intravenous immunoglobulin (IVIG).

Long chain polyunsaturated fatty acid supplementation in infancy increases length- and weight-for-age but not BMI to 6 years when controlling for effects of maternal smoking

Long chain polyunsaturated fatty acids (LCPUFA) are added to infant formula but their effect on long-term growth of children is under studied. We evaluated the effects of feeding LCPUFA-supplemented formula (n = 54) compared to control formula (n = 15) throughout infancy on growth from birth-6 years. Growth was described using separate models developed with the MIXED procedure of SAS(®) that included maternal smoking history and gender. Compared to children fed control formula, children who consumed LCPUFA supplemented formula had higher length-/stature-/and weight-for-age percentiles but not body mass index (BMI) percentile from birth to 6 years. Maternal smoking predicted lower stature (2-6 years), higher weight-for-length (birth-18 months) and BMI percentile (2-6 years) independent of LCPUFA effects. Gender interacted with the effect of LCPUFA on stature, and the relationship between smoking and BMI, with a larger effect for boys. Energy intake did not explain growth differences. A relatively small control sample is a limitation.

Discrimination learning during the first year: stimulus and positional cues

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues.

Establishing pharmaceutical care services in an HIV clinic

OBJECTIVE

To present a brief overview of human immunodeficiency virus (HIV) infection and to describe the implementation of pharmaceutical care services for adult patients with HIV infection.

SETTING

University hospital clinic.

PRACTICE DESCRIPTION

A pharmacist joined a multidisciplinary team serving HIV-infected patients in January 1994.

PRACTICE INNOVATION

Current pharmacy services include taking medication histories, educating patients, counseling patients on compliance, monitoring response to therapy, identifying drug-related problems, documenting all interventions, and making therapeutic decisions and formulary choices. The pharmacist also participates in research.

INTERVENTIONS

The pharmacist sees patients immediately after their physician appointments. Patients with one or more of the following characteristics are targeted to receive pharmaceutical care: multiple drugs, history of noncompliance, initiation of new drug therapy, recently discharged from hospital or emergency department, identification of potential adverse effects, identification of potential drug-drug interactions, and presence of drug toxicities.

CONCLUSION

Pharmacists are uniquely qualified to provide a wide range of pharmaceutical care services to HIV-positive patients. Pharmacy interventions should lead to improved outcomes and decreased costs for a chronic and very expensive disease.