Ob/Gynecology Department, SARA Research Center, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America.
Department of Internal Medicine I, University Hospital Tübingen, Tübingen, Germany.
PLoS One. 2020 Jul 22;15(7):e0235310. doi: 10.1371/journal.pone.0235310. eCollection 2020.
Auditory steady-state responses (ASSRs) are ongoing evoked brain responses to continuous auditory stimuli that play a role for auditory processing of complex sounds and speech perception. Transient auditory event-related responses (AERRs) have previously been recorded using fetal magnetoencephalography (fMEG) but involve different neurological pathways. Previous studies in children and adults demonstrated that the cortical components of the ASSR are significantly affected by state of consciousness and by maturational changes in neonates and young infants. To our knowledge, this is the first study to investigate ASSRs in human fetuses.
47 fMEG sessions were conducted with 24 healthy pregnant women in three gestational age groups (30-32 weeks, 33-35 weeks and 36-39 weeks). The stimulation consisted of amplitude-modulated (AM) tones with a duration of one second, a carrier frequency (CF) of 500 Hz and a modulation frequency (MF) of 27 Hz or 42 Hz. Both tones were presented in a random order with equal probability adding up to 80-100 repetitions per tone. The ASSR across trials was quantified by assessing phase synchrony in the cortical signals at the stimulation frequency.
Ten out of 47 recordings were excluded due to technical problems or maternal movements. Analysis of the included 37 fetal recordings revealed a statistically significant response for the phase coherence between trials for the MF of 27 Hz but not for 42 Hz. An exploratory subgroup analysis moreover suggested an advantage in detectability for fetal behavioral state 2F (active asleep) compared to 1F (quiet asleep) detected using fetal heart rate. In conclusion, this pilot study is the first description of a method to detect human ASSRs in fetuses. The findings warrant further investigations of the developing fetal brain.
听觉稳态响应（ASSR）是对连续听觉刺激产生的持续诱发脑反应，在复杂声音的听觉处理和言语感知中发挥作用。瞬态听觉事件相关反应（AERR）以前曾使用胎儿脑磁图（fMEG）记录，但涉及不同的神经通路。先前在儿童和成人中的研究表明，ASSR 的皮质成分受意识状态以及新生儿和婴儿期的成熟变化显著影响。据我们所知，这是第一项研究人类胎儿 ASSR 的研究。
对 24 名健康孕妇在三个孕龄组（30-32 周、33-35 周和 36-39 周）进行了 47 次 fMEG 检查。刺激由持续时间为 1 秒、载波频率（CF）为 500Hz 和调制频率（MF）为 27Hz 或 42Hz 的调幅（AM）音组成。两种音调以相等的概率随机呈现，每种音调加起来有 80-100 次重复。通过评估刺激频率下皮质信号的相位同步来量化跨试验的 ASSR。
由于技术问题或母体运动，有 10 个记录被排除在外。对纳入的 37 个胎儿记录进行分析，结果显示 27Hz MF 的试验间相位相干性有统计学意义的反应，但 42Hz MF 则没有。此外，一项探索性亚组分析表明，与使用胎儿心率检测到的安静睡眠 1 期（1F）相比，活跃睡眠 2 期（2F）的胎儿行为状态在检测上具有优势。总之，这项初步研究是首次描述在胎儿中检测 ASSR 的方法。这些发现值得进一步研究胎儿大脑的发育情况。
