ALTERED BRAIN-DEVELOPMENT IN TURNERS SYNDROME - AN EVENT-RELATED POTENTIAL STUDY

We compared event-related brain potentials (ERPs) and reaction time (R T) measures from untreated young (prepubertal and peripubertal; ages 9 to 14) and old (postpubertal; ages 15 to 20) Turner's syndrome (TS) s ubjects with those from normal age-matched controls. Comparisons among groups permitted the assessment of the relative roles of congenital a nd maturational brain alterations as possible bases of the cognitive d eficits in TS. All subjects were presented with series of auditory sti muli, and they either counted one of the two stimuli or made rapid dis criminative button presses to both. The results indicated that, wherea s the ERPs in young TS females were essentially the same as those in t heir age-matched controls, the ERPs in old TS females more closely res embled those in both young groups than those in their age-matched cont rols. Specifically, a late (400 to 900 msec) frontal negative slow wav e (Nc) in the old TS subjects failed to show the normal maturational c ourse in which the amplitude and duration of this component steadily d ecreases with age. Except for slightly greater amounts of N1 amplitude in the young TS group, the latencies, amplitudes, and scalp distribut ions of the other ERP components (N1, P2, N2, P300) were all the same at all ages in the TS subjects and their controls. Behaviorally, both TS groups had longer RTs than their controls but, consistent with the ERP results, they did not make more errors. The ERP and RT results poi nt to the existence of two kinds of abnormalities in TS females, each from a different mechanism: the ERP results suggest an age-dependent m aturational defect while the RT results suggest an age-independent con genital defect.