Department of Speech, Language, and Hearing Science, University of Florida, 1225 Center Drive Room 2130, Gainesville, FL, 32160, USA.
Institute for Learning & Brain Sciences, University of Washington, Seattle, WA, USA.
Brain Topogr. 2023 Sep;36(5):686-697. doi: 10.1007/s10548-023-00981-w. Epub 2023 Jul 1.
Functional near-infrared spectroscopy (fNIRS) is a viable non-invasive technique for functional neuroimaging in the cochlear implant (CI) population; however, the effects of acoustic stimulus features on the fNIRS signal have not been thoroughly examined. This study examined the effect of stimulus level on fNIRS responses in adults with normal hearing or bilateral CIs. We hypothesized that fNIRS responses would correlate with both stimulus level and subjective loudness ratings, but that the correlation would be weaker with CIs due to the compression of acoustic input to electric output.
Thirteen adults with bilateral CIs and 16 with normal hearing (NH) completed the study. Signal-correlated noise, a speech-shaped noise modulated by the temporal envelope of speech stimuli, was used to determine the effect of stimulus level in an unintelligible speech-like stimulus between the range of soft to loud speech. Cortical activity in the left hemisphere was recorded.
Results indicated a positive correlation of cortical activation in the left superior temporal gyrus with stimulus level in both NH and CI listeners with an additional correlation between cortical activity and perceived loudness for the CI group. The results are consistent with the literature and our hypothesis.
These results support the potential of fNIRS to examine auditory stimulus level effects at a group level and the importance of controlling for stimulus level and loudness in speech recognition studies. Further research is needed to better understand cortical activation patterns for speech recognition as a function of both stimulus presentation level and perceived loudness.
功能性近红外光谱（fNIRS）是一种可行的非侵入性技术，可用于耳蜗植入（CI）人群的功能神经影像学；然而，声刺激特征对 fNIRS 信号的影响尚未得到彻底研究。本研究检查了刺激水平对正常听力或双侧 CI 成人 fNIRS 反应的影响。我们假设 fNIRS 反应将与刺激水平和主观响度评分相关，但由于输入到输出的声能压缩，与 CI 的相关性较弱。
13 名双侧 CI 成人和 16 名正常听力（NH）成人完成了研究。使用语音形噪声，这是一种由语音刺激的时变包络调制的噪声，来确定在从柔和到响亮的语音范围内的难以理解的类语音刺激中，刺激水平的影响。记录左侧大脑半球的皮层活动。
结果表明，左侧颞上回的皮层激活与 NH 和 CI 受试者的刺激水平呈正相关，CI 组的皮层活动与感知的响度之间存在额外的相关性。结果与文献和我们的假设一致。
这些结果支持 fNIRS 有潜力在群体水平上检查听觉刺激水平效应，并支持在语音识别研究中控制刺激水平和响度的重要性。需要进一步研究以更好地理解作为刺激呈现水平和感知响度函数的语音识别的皮层激活模式。
