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J Colombo

Publications and source records attributed to J Colombo.

At least 19 recordsLinked to original sources
PubMed2001

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.

Cognition↗
PubMed2001

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.

Arousal↗
PubMed2001

Infants' detection of contingency: a cognitive-neuroscience perspective.

Advances in developmental cognitive neuroscience have generated important and interesting data that are relevant to infants' perception of contingencies. The author discusses concepts of "binding" (i.e., the binding of stimulus properties across space, and binding of events across time) within the context of the cognitive-neuroscience approach to learning. Issues relevant to infant contingency perception are also addressed. Previously published data on infant contingency perception and discrimination learning from the author's laboratory are reinterpreted in terms of these binding concepts, as well as the development of the neural substrates that presumably underlie the perception of stimulus attributes and temporal redundancy.

Association Learning↗
PubMed1999

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.

Acoustic Impedance Tests↗
PubMed1998

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.

Analysis of Variance↗
PubMed1997

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.

Arousal↗
PubMed1996

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.

Animals↗
PubMed1996

Individual differences in infant visual attention: recognition of degraded visual forms by four-month-olds.

In 5 experiments, 4-month-old infants were tested for their ability to recognize degraded visual targets as a function of individual differences in fixation duration. Targets were degraded by removing 10% of the total contour either from vertices (vertex-absent) or from midsegments (vertex-present). Both qualitative and quantitative differences were found in long and short lookers' ability to recognize the degraded forms. Short-looking infants were able to recognize degraded forms in both vertex-absent and vertex-present conditions, but the vertex-absent discrimination was more difficult. Long-looking infants required longer familiarization times before showing evidence of recognition in the vertex-present condition, and were unable to recognize targets in which contour was removed at vertices. The findings are discussed within the framework of the persistence of early visual processing strategies, and reliance of long-looking infants on particular local elements in visual analysis.

Attention↗
PubMed1994

The nature and processes of preverbal learning: implications from nine-month-old infants' discrimination problem solving.

Nine-month-old infants' performance on discrimination-learning problems was investigated in four experiments using the synchronous reinforcement paradigm. These experiments were organized around basic theoretical postulates concerning the relation between attention and learning. In each of the experiments, infants were trained to respond differentially to a particular stimulus feature, with the goal of establishing whether they could learn to respond to a particular stimulus feature under conditions where other stimulus dimensions were present and varying. In the first experiment, 48 infants were trained to fixate visually on a particular feature in a pair of stimuli that varied in color, form, and position dimensions. Contingencies for responding were then shifted either within a dimension (reversal shift) or across dimensions (nonreversal shift). Infants learned to respond to the reinforced feature during initial training; moreover, infants assigned to a reversal shift condition showed a higher level of transfer of learning during the test phase than those assigned to a nonreversal shift condition. The second experiment extended the results of Experiment 1 by testing 48 additional infants under conditions in which the number of varying irrelevant dimensions was increased during the shift phase. Although the difficulty added to this task by this manipulation made transfer more difficult for all infants, results again indicated that transfer of learning was more evident for infants in a reversal shift than a nonreversal shift condition. In the third experiment, 64 infants were trained in a similar manner, except that completely new values were substituted during shift phases on the color and form dimensions. This manipulation was meant to probe whether infants were formulating a dimension response from previous training and to test the predictions of such dimension processing for transfer of learning to a functionally new problem. Infants were reinforced for fixating on a new feature either within the same dimension as during training (intradimension shift) or within the dimension that was not originally trained (extradimension shift). Transfer of learning was clearly superior in the intradimension shift condition. The findings of the first three experiments suggested that, during discrimination-learning problems, infants selected and tested individual stimulus features and dimensions from an array of potential solutions to the problem until discovering the one that was consistently associated with reinforcement.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

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.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

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.

Carcinoma, Squamous Cell↗
PubMed1993

Individual differences in infant visual attention: four-month-olds' discrimination and generalization of global and local stimulus properties.

Cognitive performance and development is negatively correlated with fixation duration patterns during infancy, and evidence suggests that long-looking infants may process visual information more slowly than short-looking infants. 3 experiments described here tested the possibility that these differences may be due to differential sensitivity to global and local visual information. Infants were administered discrimination and generalization tasks involving global and local information at varying levels of familiarization time. Results indicated that 4-month-olds process visual information in a global-to-local sequence. Both long- and short-looking infants were sensitive to both types of information, although long lookers required additional familiarization time to match the performance of short lookers. Finally, apparent "generalization" of global information at brief familiarization levels was traced to insensitivity to local stimulus properties. The results do not support the hypothesis that long- and short-looking infants are differentially sensitive to global versus local visual information at 4 months of age.

Attention↗
PubMed1991

Individual differences in infant visual attention: are short lookers faster processors or feature processors?

Individual differences in the duration of infants' visual fixations are reliable and stable and have been linked to differential cognitive performance; short-looking infants typically perform better than long-looking infants. 4 experiments tested the possibility of whether short lookers' superiority on perceptual-cognitive tasks is attributable to attention to the featural details of visual stimuli, or simply to differences in the speed or efficiency of visual processing. To do this, the performance of long- and short-looking 4-month-olds was examined on separate discrimination tasks that could be solved only by processing either featural or global information. The global task was easier than the featural task, but as the amount of time allotted for infants to solve either type of task was decreased, short lookers' performance was superior to that of long lookers. These results thus lend support to a speed or efficiency of stimulus processing interpretation of infant fixation duration.

Attention↗
PubMed1990

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.

Attention↗
PubMed1990

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.

Attention↗
PubMed1989

Neonatal state profiles: reliability and short-term prediction of neurobehavioral status.

Observations were made on 40 newborns prior to hospital discharge in which states were scored every 10 sec in two 35-70-min periods separated by 6-48 hours. Newborns' states, particularly sleep states and crying, were fairly reliable across observation sessions. Cluster analyses identified 3 separable state profiles that subsequently differentiated infants on the Neonatal Behavioral Assessment Scale with Kansas Supplements (NBAS-K) at 2 weeks of age. Additionally, state observations and NBAS-K exams showed significant agreement on individual differences in neurologically based measures, such as startles, tremulousness, and lability of state.

Arousal↗
PubMed1988

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.

Attention↗