Visual memory and learning in extremely low-birth-weight/extremely preterm adolescents compared with controls: a geographic study.

BACKGROUND: Contemporary data on visual memory and learning in survivors born extremely preterm (EP; <28 weeks gestation) or with extremely low birth weight (ELBW; <1,000 g) are lacking. METHODS: Geographically determined cohort study of 298 consecutive EP/ELBW survivors born in 1991 and 1992, and 262 randomly selected normal-birth-weight controls. RESULTS: Visual learning and memory data were available for 221 (74.2%) EP/ELBW subjects and 159 (60.7%) controls. EP/ELBW adolescents exhibited significantly poorer performance across visual memory and learning variables compared with controls. Visual learning and delayed visual memory were particularly problematic and remained so after controlling for visual-motor integration and visual perception and excluding adolescents with neurosensory disability, and/or IQ <70. Male EP/ELBW adolescents or those treated with corticosteroids had poorer outcomes. CONCLUSION: EP/ELBW adolescents have poorer visual memory and learning outcomes compared with controls, which cannot be entirely explained by poor visual perceptual or visual constructional skills or intellectual impairment.

Effects of correcting for prematurity on cognitive test scores in childhood.

AIMS: The American Academy of Pediatrics recommends that test scores should be corrected for prematurity up to 3 years of age, but this practice varies greatly in both clinical and research settings. The aim of this study was to contrast the effects of using chronological age and those of using corrected age on measures of cognitive outcome across childhood. METHODS: A theoretical model was constructed using norms from the Bayley Scales of Infant and Toddler Development, Third Edition; the Wechsler Preschool and Primary Scale of Intelligence, Third Edition Australian; and the Wechsler Intelligence Scales for Children, Fourth Edition Australian. Baseline scores representing different levels of functioning (70, below average; 85, borderline; and 100, average) were recalculated using the normative data for ages 6 months to 16 years to account for 1, 2, 3 and 4 months of prematurity. The model created depicted the difference in standardised scores between chronological and corrected age. RESULTS: Compared with scores corrected for prematurity, the absolute reduction in scores using chronological age was greater for increasing degree of prematurity, younger ages at assessment and higher baseline scores and was substantial even beyond 3 years of age. However, the pattern was erratic, with considerable fluctuation evident across different ages and baseline scores. CONCLUSIONS: Chronological age results in a lowering of scores at all ages for preterm-born subjects that is greater in the first few years and in those born at earlier gestational ages. Whether or not to correct for prematurity depends upon the context of the assessment.

Attention difficulties in a contemporary geographic cohort of adolescents born extremely preterm/extremely low birth weight.

The aim of this study was to evaluate attention difficulties in a contemporary geographic cohort of adolescents born extremely preterm (EP, <28 weeks' gestation) or extremely low birth weight (ELBW, birth weight <1000 g). The EP/ELBW group included 228 adolescents (mean age = 17.0 years) born in Victoria, Australia in 1991 and 1992. The control group were 166 adolescents (mean age = 17.4 years) born of normal birth weight (birth weight >2499 g) who were recruited in the newborn period and matched to the EP/ELBW group on date of birth, gender, language spoken and health insurance status. Participants were assessed on measures of selective, sustained, and executive (shift and divided) attention, and parents and participants completed behavioral reports. The EP/ELBW group performed more poorly across tests of selective and executive attention, had greater rates of clinically significant difficulties compared with the control group, and also had greater behavioral attention problems as reported by parents. Neonatal risk factors were weakly associated with attention outcomes. In conclusion, higher rates of attention impairments are observed in individuals born EP/ELBW well into adolescence and may have consequences for their transition to adulthood.

Deficits in selective attention in symptomatic Huntington disease: assessment using an attentional blink paradigm.

BACKGROUND: Impaired selective attention in Huntington disease (HD) may manifest as difficulty in identifying a single target embedded among a series of distractors in rapid serial visual presentation tasks. METHOD: We used an attentional blink (AB) paradigm to examine whether attentional control is impaired in symptomatic HD. Fourteen HD patients and 13 age-matched healthy controls performed a rapid serial visual presentation task in which 2 targets (T1 and T2) and numerous distractors were presented in rapid succession. We assessed the accuracy of T1 identification and the AB (impaired T2 detection after the correct identification of T1). RESULTS: Among the HD patients, identification of T1 was significantly impaired and AB was significantly larger but not longer. The HD patients also made significantly more random errors. CONCLUSIONS: Frontostriatal or frontoparietal dysfunction is likely to compromise attentional control in HD, such that well-masked and rapidly presented target stimuli are difficult to detect and identify, especially as the difficulty level increases. Although we previously reported no AB deficits in presymptomatic HD, with manifest disease we found that the progressive frontoparietal cortical changes compromise attentional control mechanisms.

Visual processing in adolescents born extremely low birth weight and/or extremely preterm.

BACKGROUND AND OBJECTIVES: Ocular growth and development differs between preterm and term-born infants and may cause long-term negative consequences for visual function, but contemporary data on long-term visual outcomes in representative samples of the highest risk extremely low birth weight (ELBW, <1000 g birth weight) or extremely preterm (EP, <28 weeks' gestation) survivors are lacking. Our objective was to compare visual functioning between ELBW/EP and normal birth weight (NBW, >2499 g birth weight) control adolescents. METHODS: Geographically determined cohort study of 228 consecutive ELBW/EP survivors born in the state of Victoria in 1991 and 1992, and 166 randomly selected NBW controls assessed between 14 and 20 years of age. Visual acuity, stereopsis, convergence, color perception, and visual perception were assessed and contrasted between groups. RESULTS: ELBW/EP subjects had significantly worse visual acuity with habitual correction in both the left and right eyes, and for the best eye (P < .001). The ELBW/EP adolescents also exhibited poorer stereopsis, odds ratio (OR) 3.22 (95% confidence interval [CI] 1.78 to 5.84), and convergence, OR 2.76 (CI 1.32 to 5.75) than controls, and more problems with visual perception, OR 3.09 (CI 1.67 to 5.71) after habitual correction. CONCLUSIONS: Despite advances in medical care improving the survival rate of high-risk ELBW/EP infants, visual morbidity is still relatively high compared with controls in late adolescence.

Contribution of brain size to IQ and educational underperformance in extremely preterm adolescents.

OBJECTIVES: Extremely preterm (EP) survivors have smaller brains, lower IQ, and worse educational achievement than their term-born peers. The contribution of smaller brain size to the IQ and educational disadvantages of EP is unknown. This study aimed (i) to compare brain volumes from multiple brain tissues and structures between EP-born (< 28 weeks) and term-born (≥ 37 weeks) control adolescents, (ii) to explore the relationships of brain tissue volumes with IQ and basic educational skills and whether this differed by group, and (iii) to explore how much total brain tissue volume explains the underperformance of EP adolescents compared with controls. METHODS: Longitudinal cohort study of 148 EP and 132 term controls born in Victoria, Australia in 1991-92. At age 18, magnetic resonance imaging-determined brain volumes of multiple tissues and structures were calculated. IQ and educational skills were measured using the Wechsler Abbreviated Scale of Intelligence (WASI) and the Wide Range Achievement Test(WRAT-4), respectively. RESULTS: Brain volumes were smaller in EP adolescents compared with controls (mean difference [95% confidence interval] of -5.9% [-8.0, -3.7%] for total brain tissue volume). The largest relative differences were noted in the thalamus and hippocampus. The EP group had lower IQs(-11.9 [-15.4, -8.5]), spelling(-8.0 [-11.5, -4.6]), math computation(-10.3 [-13.7, -6.9]) and word reading(-5.6 [-8.8, -2.4]) scores than controls; all p-values<0.001. Volumes of total brain tissue and other brain tissues and structures correlated positively with IQ and educational skills, a relationship that was similar for both the EP and controls. Total brain tissue volume explained between 20-40% of the IQ and educational outcome differences between EP and controls. CONCLUSIONS: EP adolescents had smaller brain volumes, lower IQs and poorer educational performance than controls. Brain volumes of multiple tissues and structures are related to IQ and educational outcomes. Smaller total brain tissue volume is an important contributor to the cognitive and educational underperformance of adolescents born EP.