Adverse effects of fetal cocaine exposure on neonatal auditory information processing.

BACKGROUND: Studies with animals have shown that in utero exposure to cocaine interferes with fetal brain development by disrupting the processes of neuronal proliferation, differentiation, and migration, often leading to subsequent neurobehavioral deficits. However, studies with humans have produced inconsistent findings. Although neurobehavioral abnormalities have been observed among cocaine-exposed infants in several studies and in some cases dose-response effects have been found, the specific neurobehaviors affected vary from one study to the next. Researchers studying the effects of fetal cocaine-exposure are faced with many difficult challenges. For example, women who use cocaine typically use other substances in addition to cocaine, many of the methods available for identifying cocaine-exposed neonates are not reliable, and the available methods for assessing cocaine-exposed newborns may not be sufficiently sensitive to detect the subtle effects of cocaine on the developing central nervous system. Despite these difficulties, there is a growing body of research that suggests that fetal cocaine exposure is associated with subsequent language deficits among children exposed in utero. However, it is virtually impossible to disentangle the effects of the impoverished environments in which these children are often raised from the effect, if any, of fetal cocaine exposure. To determine the effects of fetal cocaine exposure independent of postnatal environmental effects, cocaine-exposed neonates would ideally be tested within the first few weeks of birth, and to identify early risks for subsequent language delay, well-researched auditory information processing measures could be used. OBJECTIVE: The purpose of the present study was to assess the effects of fetal cocaine exposure on neonatal auditory information processing ability. To overcome limitations of some previous studies on the neuroteratogenic effects of cocaine, such as unreliable subject identification techniques, inadequate control over confounding variables, and questionable measures of central nervous system integrity, a valid measure of auditory information processing was used in a rigorous, case-control design. METHOD: Newborn information processing was assessed using habituation and recovery of head-turning toward an auditory stimulus across the 3 phases of the procedure: familiarization, novelty, and dishabituation. During the familiarization phase, the infant orients and habituates to a repeated word; during the novelty phase, the infant recovers head-turning to a novel word and subsequently habituates to this word; and during the dishabituation phase the infant displays renewed head-turning to the return of the original stimulus. Testing takes approximately 20 minutes. This procedure has been shown previously to discriminate among infants at high-, moderate-, and low-risk for subsequent developmental delay. Twenty-five cocaine-exposed and 25 nonexposed control neonates, identified by meconium analysis, urine analysis, and/or maternal self-report, were tested on the auditory information processing procedure. The majority of infants were tested within the first few days of birth. Cocaine-exposed and control neonates were matched on birth weight, gestational age, Apgar scores, age at testing, and socioeconomic status as reflected by household income. Mothers were matched on age, weight gain, cigarette smoking, and alcohol consumption. RESULTS: Fetal cocaine exposure was associated with impaired auditory information processing. Both cocaine-exposed and nonexposed control neonates oriented to the familiarization stimulus, but cocaine-exposed neonates displayed impaired habituation. Moreover, cocaine-exposed neonates did not recover or habituate to the novel stimulus or dishabituate to the return of the familiarization stimulus. (ABSTRACT TRUNCATED)

Maternal cocaine use without evidence of fetal exposure.

We report a case of lack of fetal exposure to cocaine and benzoylecgonine as evidenced by meconium and hair analysis, but exposure to nicotine and its metabolite cotinine, after extensive maternal use of cocaine and nicotine. These data suggest that the mode of maternal use of cocaine and individual differences in placental handling of the drug may protect some fetuses, and highlight the need to address interpatient variability.

Newborn response to auditory stimulus discrepancy.

Newborns were assessed for their recovery of head turning toward laterally presented auditory stimuli (titi) that varied from a familiar standard on 1 of 5 levels of fundamental frequency. Following habituation to repeated standard trials, newborns recovered to 14% and 21%, but not to 0%, 7%, or 28% discrepancies, indicating that recovery was a quadratic function of the degree of stimulus-schema discrepancy. Moreover, newborns reliably turned away from the standard stimulus during posthabituation no-change control trials, indicating that the neural network associated with that stimulus was not fatigued. Infants in every condition showed recovery of head turning to a novel posttest stimulus (papa). These data are interpreted with a dual processing model postulated to include both reflexive (context-independent) orientation and stimulus-schema comparison process (context-dependent) orientation.

The development of walking: new findings and old assumptions.

I have argued that a behavioral-cognitive perspective may shed light on some aspects of motor development generally, and unaided walking, specifically. Individual components of walking-stepping, standing, and placing, for example-are present at birth and can be maintained with practice. Moreover, consistent use can produce an earlier onset of unaided walking. Nonetheless, independent erect locomotion rarely occurs before about 9 months in most societies, implying that there is a maturational constraint. Independent research on changes in the quality of object use imply that the maturational limitation may be cognitive, in part. Changes in motor development-both the onset of unaided walking and the emergence of functional use-may be dictated by an underlying change in information processing ability. It is hypothesized that the infant's capacity to generate ideas or access different associations from memory rapidly may define the nature of this change. Improved access to memory may permit the necessary integrative capacity for balance and coordination to occur, thereby permitting unaided walking to develop. Weiss and Zelazo found that the capacity to perform two distinct actions in rapid succession in an independent environment-water-also appears to emerge from about 9 through 12 months. Not only may a cognitive change influence motor development, but mental and motor ability may develop asynchronously in some instances-a particularly important implication for developmental assessment. Procedures to distinguish information processing ability independent of gross and fine motor measures and productive language can lead to treatment that will reduce delays on conventional tests and contribute to the validity of this argument.

Infant reaction to parental separations when left with familiar and unfamiliar adults.

The results of two experiments examining infants at 6, 9, 12, 15, 18, and 21 months of age and varying levels of father interaction are summarized to show that separation protest is more a function of a strange person remaining in an unfamiliar laboratory situation with the infant than the temporary loss of a specific parent. The use of protest as an index of infant-parent attachment seems undesirable.

Separation protest in day-care and home-reared infants.

Separation protest was measured by the onset and duration of fretting or crying in 24 day-care and 28 home-reared infants during a two-minute period of isolated separation from their mothers in an unfamiliar room. Separation episodes were repeated under similarly controlled circumstances at two-month intervals from 3 1/2 through 13 1/2 months and at 20 months of age. The composition of the day-care and home-reared groups was similar for sex, ordinal position, and family background. Day-care and home-reared infants showed similar patterns in the manifestation of separation protest over age, with sharp reductions in latency to crying and marked increases in the occurrence of crying at 9 1/2 and 13 1/2 months. These results suggest that the psychological processes underlying separation protest are not materially altered by the continuing presence of the young infant in a day-care program designed to meet both his physical and psychological requirements.

"Walking" in the newborn.

Brief daily exercise of the walking and placing reflexes in the newborn leads to a high rate of responding by 8 weeks and to an earlier onset of walking alone. There appears to be a critical period during which the walking response can be transformed intac from a reflexive to an instrumental action.