Rapid-FFR: Developing a rapid method of measuring the auditory frequency following response for use in children and infants

听力学临床中最常用的电生理方法是短声诱发的听性脑干反应(ABR)。在新生儿听力筛查计划中广泛使用，它的优势是只需2-3分钟测量(一旦放置电极)，这是测试婴儿和儿童时的一个重要考虑因素。虽然有很大的用处，但从这样一个简单的刺激可以在短时间内获得的信息是有限的，而且短声诱发的ABR大多被用来检测听力损失。最近，人们对另一种听觉反应，即所谓的频率跟随反应(FFR)的兴趣越来越大。FFR是一种头皮记录的电生理测量，它反映了沿听觉通路对周期性听觉刺激做出反应的持续同步神经放电。最近的证据表明，通过改变刺激的基频(F0)，有可能有利于听觉通路不同水平的神经生成器，相对较低的频率F0导致更多的皮质贡献，而较高频率的F0加权较低水平的脑干贡献。此外，使用这种技术，发出的声音在声学上可能比点击复杂得多，即使包括语音也是如此。由于可以探索更多种类的声学属性，因此可以比相对粗略的点击ABR更具体地瞄准各种语音相关特征。最重要的是，人类和动物研究都表明，FFR和ABR测量神经生理功能的互补方面，与行为有关，以及反映不同的神经群体。简而言之，FFR可能是一种有用的工具，用于婴儿和儿童的听觉诊断，并可能允许探测听觉通路的不同阶段。测量FFR的一个重要方面阻碍了其在临床上的采用，即测量它们所需的时间。FFR通常被记录为离散的静默分离的刺激，持续时间为40-150ms，有时长达2 S。收集一个强大的FFR可能需要长达30分钟，因为它需要大约2000-3000次刺激重复，而且通常认为记录信号的正负极是可取的。这样的措施对成年参与者来说已经够繁重的了。对于婴儿和儿童，FFR所需的时间对其更广泛的使用构成了一个重要的障碍。我们一直在开发一种新的测量FFR的方法，在这种方法中，刺激连续呈现(即，没有刺激间的间隔)，并在单个反应周期内取平均值。对于我们使用的特定刺激，FFR记录时间从标准技术的大约2.5分钟减少到使用我们的新技术(Rapid-FFR)仅35秒，数据质量相当。这种获取时间的减少意味着在一个会话中测试更多的条件，以及测试难以长时间保持静止的参与者变得更容易。在这个项目中，我们建议更全面地研究这项技术在成年人中的使用，例如，改变刺激的F0，以及存在的声学特征，特别强调在言语感知中至关重要的特征。其次，我们计划将其应用于儿童和婴儿，以期使这项技术可行，以便将FFR的测量包括在听力测试电池中。

The most commonly used electrophysiological measure in the audiological clinic is that of the click-evoked Auditory Brainstem Response (ABR). Used widely in newborn hearing screening programmes, it has the advantage of taking only 2-3 minutes to measure (once the electrodes are placed), an important consideration when testing infants and children. Although of great utility, the information one can gain in a short time from such a simple stimulus is limited, and click-evoked ABRs have mostly been used to detect hearing loss.Recently, there been a growing interest in another auditory response, the so-called frequency following response (FFR). The FFR is a scalp-recorded electrophysiological measure which reflects sustained synchronous neural firing in response to periodic auditory stimuli along the auditory pathway. Recent evidence suggests that by varying the fundamental frequency (F0) of the stimuli, it is possible to favour neural generators at different levels of the auditory pathway, with relatively low frequency F0s leading to more cortical contributions, and higher frequency ones weighting lower level brainstem contributions. Also, with such a technique, evoking sounds can be much more acoustically complex than clicks, even including speech sounds. Because of the wider variety of acoustic attributes that can be explored, it is possible to target various speech-related features more specifically than is possible with a relatively crude click ABR. Most importantly, both human and animal studies show that the FFR and ABR measure complementary aspects of neurophysiological functioning, relating to behaviour differently, as well as in reflecting different neural populations. In short, FFRs could be a useful tool to use in auditory diagnoses in infants and children, and might allow the probing of different stages in the auditory pathway.One important aspect of measuring FFRs that impedes their adoption in the clinic is the time it takes to measure them. FFRs are typically recorded to discrete silence-separated stimuli with a duration of 40 - 150 ms and sometimes up to as much as 2 s. Collecting a robust FFR can take up to 30 minutes as it requires approximately 2000-3000 repetitions of the stimulus, and it is often considered desirable to record both positive and negative polarities of the signal. Such measures are onerous enough in adult participants. For infants and children, the time required for FFRs poses an important obstacle to their more general use.We have been developing a new method for measuring FFRs, in which the stimulus is presented continuously (i.e., without an interstimulus interval) and averaging across a single cycle of the response. For the particular stimulus we used, FFR recording times were reduced from approximately 2.5 minutes for the standard technique to only 35 seconds using our new one (Rapid-FFR), with comparable data quality. This reduction in acquisition time means that that it becomes easier to test a larger number of conditions within one session and to test participants who have difficulty remaining still for a long time. In this project, we propose to investigate more fully the use of this technique in adults, varying, for example, the F0 of the stimuli, as well as the acoustic features present, with a particular emphasis on features crucial in speech perception. Secondly, we plan to apply it in children and infants, with a view towards making the technique viable for measurements of the FFR to be included in audiological test batteries.