Central and peripheral timing variability in children with heavy prenatal alcohol exposure.

Background: The study examined whether prenatal alcohol exposure is associated with increased motor timing variability when the timing response is partitioned into central clock variability, which indexes information processing at the central nervous system (CNS) level and motor delay variability, which reflects timing processes at the level of the peripheral nervous system.

Methods: Eighteen children with histories of prenatal alcohol exposure and 22 control children were assigned to young (7 to 11 years) or older (12 to 17 years) groups. Children tapped a single response key with the index finger in synchrony with a series of externally generated tones (the paced phase). At the conclusion of these tones, children continued tapping (the continuation phase) while attempting to maintain the same rate of tapping imposed by the paced phase. Two blocks of tapping were completed with inter-tone-intervals set at either 400 or 900 milliseconds. Inter-response interval, central clock variability, and motor delay variability produced during the continuation phase were the dependent variables.

Results: Mean inter-response interval for the 4 groups did not differ for either time interval. Central clock variability produced by the young alcohol-exposed group was significantly greater than the two older groups for the 400 millisecond interval and all other groups for the 900 millisecond interval. Motor delay variability produced by the young alcohol-exposed group was significantly greater than the other three groups for both time intervals. Central and motor delay variability in children with and without alcohol exposure was directly related to the duration of the interval to be reproduced.

Conclusions: Central and peripheral timing variability was significantly greater for the young alcohol-exposed children. This atypical timing may be related to the teratogenic effects of alcohol, although the negative effects are limited to younger alcohol-exposed children since there were no differences in central and peripheral timing variability between the older alcohol-exposed children and controls.