Effects of Alcohol on Functional Development of the Auditory Pathway in the Brainstem of Infants and Chick Embryos

Abstract

The effects of alcohol on the development of neural function in the auditory pathway of the brainstem have been examined in human neonates and chick embryos. Auditory brainstem evoked responses were recorded in six infants of mothers for whom there was evidence of alcohol abuse during pregnancy. In four of the infants, evoked responses were abnormal, with poorly defined, inconsistent peaks. Neurophysiological and histological studies were done on chick embryos which received a single dose of alcohol early incubation. In most surviving embryos the neuroanatomical arrangement of the auditory nuclei in the brainstem was normal. However, Golgi impregnation revealed abnormalities in the length and structure of the dendrites in nucleus laminaris. Electrically evoked neuronal activity revealed abnormalities of synaptic function and the distribution of nerve terminals. The results indicate that in infants and chick embryos the functional development of the auditory pathway in the brainstem is disrupted by exposure to alcohol. Such early changes in this sensory pathway may contribute to the behavioural and intellectual handicaps associated with the fetal alcohol syndrome.