Shader Maureen J, Luke Robert, Gouailhardou Nathalie, McKay Colette M
Bionics Institute, 384-388 Albert Street, East Melbourne, Victoria 3002, Australia; Department of Medical Bionics, The University of Melbourne, Grattan Street, Parkville, Victoria 3010, Australia.
Bionics Institute, 384-388 Albert Street, East Melbourne, Victoria 3002, Australia; Department of Linguistics, Faculty of Medicine, Health and Human Sciences, Macquarie Hearing, Macquarie University, 16 University Avenue, New South Wales 2109, Australia.
Hear Res. 2021 Jul;406:108256. doi: 10.1016/j.heares.2021.108256. Epub 2021 Apr 28.
As an alternative to fMRI, functional near-infrared spectroscopy (fNIRS) is a relatively new tool for observing cortical activation. However, spatial resolution is reduced compared to fMRI and often the exact locations of fNIRS optodes and specific anatomical information is not known. The aim of this study was to explore the location and range of specific regions of interest that are sensitive to detecting cortical activation using fNIRS in response to auditory- and visual-only connected speech. Two approaches to a priori region-of-interest selection were explored. First, broad regions corresponding to the auditory cortex and occipital lobe were analysed. Next, the fNIRS Optode Location Decider (fOLD) tool was used to divide the auditory and visual regions into two subregions corresponding to distinct anatomical structures. The Auditory-A and -B regions corresponded to Heschl's gyrus and planum temporale, respectively. The Visual-A region corresponded to the superior occipital gyrus and the cuneus, and the Visual-B region corresponded to the middle occipital gyrus. The experimental stimulus consisted of a connected speech signal segmented into 12.5-sec blocks and was presented in either an auditory-only or visual-only condition. Group-level results for eight normal-hearing adult participants averaged over the broad regions of interest revealed significant auditory-evoked activation for both the left and right broad auditory regions of interest. No significant activity was observed for any other broad region of interest in response to any stimulus condition. When divided into subregions, there was a significant positive auditory-evoked response in the left and right Auditory-A regions, suggesting activation near the primary auditory cortex in response to auditory-only speech. There was a significant positive visual-evoked response in the Visual-B region, suggesting middle occipital gyrus activation in response to visual-only speech. In the Visual-A region, however, there was a significant negative visual-evoked response. This result suggests a significant decrease in oxygenated hemoglobin in the superior occipital gyrus as well as the cuneus in response to visual-only speech. Distinct response characteristics, either positive or negative, in adjacent subregions within the temporal and occipital lobes were fairly consistent on the individual level. Results suggest that temporal regions near Heschl's gyrus may be the most advantageous location in adults for identifying hemodynamic responses to complex auditory speech signals using fNIRS. In the occipital lobe, regions corresponding to the facial processing pathway may prove advantageous for measuring positive responses to visual speech using fNIRS.
作为功能磁共振成像（fMRI）的替代方法，功能近红外光谱技术（fNIRS）是一种用于观察皮层激活的相对较新的工具。然而，与fMRI相比，其空间分辨率较低，而且fNIRS光极的确切位置和具体解剖信息通常并不清楚。本研究的目的是探索在仅听和仅视连接性言语刺激下，使用fNIRS检测皮层激活时特定感兴趣区域的位置和范围。研究探索了两种先验感兴趣区域选择方法。首先，分析了对应于听觉皮层和枕叶的广泛区域。其次，使用fNIRS光极位置判定器（fOLD）工具将听觉和视觉区域划分为对应不同解剖结构的两个子区域。听觉A区和B区分别对应于颞横回和颞平面。视觉A区对应于枕上回和楔叶，视觉B区对应于枕中回。实验刺激由分割为12.5秒片段的连接性言语信号组成，在仅听或仅视条件下呈现。对八名听力正常的成年参与者在广泛感兴趣区域上的组水平结果显示，左右两侧广泛听觉感兴趣区域均有显著的听觉诱发激活。在任何刺激条件下，其他广泛感兴趣区域均未观察到显著活动。当划分为子区域时，左右听觉A区均有显著的正向听觉诱发反应，表明在仅听言语刺激下初级听觉皮层附近被激活。视觉B区有显著的正向视觉诱发反应，表明在仅视言语刺激下枕中回被激活。然而，在视觉A区，有显著的负向视觉诱发反应。这一结果表明，在仅视言语刺激下，枕上回以及楔叶中的氧合血红蛋白显著减少。颞叶和枕叶内相邻子区域中明显的正向或负向反应特征在个体水平上相当一致。结果表明，对于成年人而言，颞横回附近的颞叶区域可能是使用fNIRS识别对复杂听觉言语信号的血流动力学反应的最有利位置。在枕叶中，对应于面部处理通路的区域可能有利于使用fNIRS测量对视觉言语的正向反应。
