Auditory evoked responses in low-birth weight infants

Abstract

Averaged auditory evoked responses (AER) were obtained bipolarly from C-O, in 13 AFD and 6 SFD infants.T he recordings were made polygraphicallyd uring natural sleep and longitudinallyf rom 30 through 49 weeks' post-conceptionala ge. The stimuli were also given separatelyd uring the“bu rst”and “flat”periods of the trace alternant
There were two types of AER wave forms. Type A consisted of initialn egative deflection (N₁) with the peak latency of about 80m sec and the following positivec omponent P₂ with latency of 2 10m sec. The first P₁ deflection was not found constantly. Type B has peaks of N₁, P₂, N₂ at 250m sec and P₃ at about 470m sec. Type A responses were mainly found in infantsy ounger than 33-34week s, post-conceptionala ge and Type B mainly in infants older than 35-36weeks (Tab.1).There was no difference in AER wave form among different background EEG patterns, sleep with trace alternant and “burst” or “Hat” period of trace alternant. The latency of the component P₂ and N₂ decreased with maturation in both sleep stages.The amplitude of N₁-P₂ decreased withpost-con-ceptional age. After 35-36 weeks, the peak latency of N₂ is significantly shorter in REM stage than those in trace alternant stage. In contrast, no difference was found in the amplitude between RE M and trac E alternant. From these resu/ts, it may be concluded that the AER is useful for the as sess ment of maturation.