Cieśla Katarzyna, Wolak Tomasz, Lorens Artur, Heimler Benedetta, Skarżyński Henryk, Amedi Amir
Institute of Physiology and Pathology of Hearing, World Hearing Center, Warsaw, Poland.
Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Faculty of Medicine, Hebrew University of Jerusalem, Hadassah Ein-Kerem, Jerusalem, Israel.
Restor Neurol Neurosci. 2019;37(2):155-166. doi: 10.3233/RNN-190898.
Hearing loss is becoming a real social and health problem. Its prevalence in the elderly is an epidemic. The risk of developing hearing loss is also growing among younger people. If left untreated, hearing loss can perpetuate development of neurodegenerative diseases, including dementia. Despite recent advancements in hearing aid (HA) and cochlear implant (CI) technologies, hearing impaired users still encounter significant practical and social challenges, with or without aids. In particular, they all struggle with understanding speech in challenging acoustic environments, especially in presence of a competing speaker.
In the current proof-of-concept study we tested whether multisensory stimulation, pairing audition and a minimal-size touch device would improve intelligibility of speech in noise.
To this aim we developed an audio-to-tactile sensory substitution device (SSD) transforming low-frequency speech signals into tactile vibrations delivered on two finger tips. Based on the inverse effectiveness law, i.e., multisensory enhancement is strongest when signal-to-noise ratio is lowest between senses, we embedded non-native language stimuli in speech-like noise and paired it with a low-frequency input conveyed through touch.
We found immediate and robust improvement in speech recognition (i.e. in the Signal-To-Noise-ratio) in the multisensory condition without any training, at a group level as well as in every participant. The reported improvement at the group-level of 6 dB was indeed major considering that an increase of 10 dB represents a doubling of the perceived loudness.
These results are especially relevant when compared to previous SSD studies showing effects in behavior only after a demanding cognitive training. We discuss the implications of our results for development of SSDs and of specific rehabilitation programs for the hearing impaired either using or not using HAs or CIs. We also discuss the potential application of such a set-up for sense augmentation, such as when learning a new language.
听力损失正成为一个切实的社会和健康问题。其在老年人中的患病率呈流行态势。在年轻人中，患听力损失的风险也在增加。如果不加以治疗，听力损失会使神经退行性疾病（包括痴呆症）的发展持续下去。尽管近年来助听器（HA）和人工耳蜗（CI）技术取得了进步，但听力受损用户无论是否使用辅助设备，仍面临重大的实际和社会挑战。特别是，他们在具有挑战性的声学环境中，尤其是在有竞争说话者的情况下，都难以理解语音。
在当前的概念验证研究中，我们测试了多感官刺激（将听觉与最小尺寸的触摸设备配对）是否会提高噪声环境下语音的可懂度。
为此，我们开发了一种音频到触觉的感官替代设备（SSD），将低频语音信号转换为在两个指尖上传递的触觉振动。基于逆有效性定律，即当感官之间的信噪比最低时，多感官增强最强，我们将非母语刺激嵌入类似语音的噪声中，并将其与通过触摸传递的低频输入配对。
我们发现，在多感官条件下，无需任何训练，无论是在群体层面还是在每个参与者中，语音识别（即信噪比）都能立即得到显著改善。考虑到10分贝的增加代表感知响度翻倍，群体层面报告的6分贝改善确实很显著。
与之前的SSD研究相比，这些结果尤其重要，之前的研究表明只有经过严格的认知训练后行为才会产生效果。我们讨论了我们的结果对SSD开发以及针对使用或不使用HA或CI的听力受损者的特定康复计划的影响。我们还讨论了这种设置在感官增强方面的潜在应用，例如学习一门新语言时。
