Zhuang Chu, Meidenbauer Kimberly L, Kardan Omid, Stier Andrew J, Choe Kyoung Whan, Cardenas-Iniguez Carlos, Huppert Theodore J, Berman Marc G
Environmental Neuroscience Lab, Department of Psychology, The University of Chicago, USA.
Environmental Neuroscience Lab, Department of Psychology, The University of Chicago, USA.
Cortex. 2022 Sep;154:62-76. doi: 10.1016/j.cortex.2022.05.009. Epub 2022 May 31.
Scale invariant neural dynamics are a relatively new but effective means of measuring changes in brain states as a result of varied cognitive load and task difficulty. This study tests whether scale invariance (as measured by the Hurst exponent, H) can be used with functional near-infrared spectroscopy (fNIRS) to quantify cognitive load, paving the way for scale-invariance to be measured in a variety of real-world settings. We analyzed H extracted from the fNIRS time series while participants completed an N-back working memory task. Consistent with what has been demonstrated in fMRI, the current results showed that scale-invariance analysis significantly differentiated between task and rest periods as calculated from both oxy- (HbO) and deoxy-hemoglobin (HbR) concentration changes. Results from both channel-averaged H and a multivariate partial least squares approach (Task PLS) demonstrated higher H during the 1-back task than the 2-back task. These results were stronger for H derived from HbR than from HbO. This suggests that scale-free brain states are a robust signature of cognitive load and not limited by the specific neuroimaging modality employed. Further, as fNIRS is relatively portable and robust to motion-related artifacts, these preliminary results shed light on the promising future of measuring cognitive load in real life settings.
尺度不变神经动力学是一种相对较新但有效的方法，用于测量由于不同认知负荷和任务难度导致的脑状态变化。本研究测试尺度不变性（由赫斯特指数H衡量）是否可与功能近红外光谱（fNIRS）一起用于量化认知负荷，为在各种现实环境中测量尺度不变性铺平道路。我们在参与者完成N-back工作记忆任务时，分析了从fNIRS时间序列中提取的H。与功能磁共振成像（fMRI）中已证明的结果一致，当前结果表明，根据氧合血红蛋白（HbO）和脱氧血红蛋白（HbR）浓度变化计算，尺度不变性分析在任务期和休息期之间有显著差异。通道平均H和多变量偏最小二乘法（任务PLS）的结果均表明，1-back任务期间的H高于2-back任务。这些结果对于从HbR得出的H比从HbO得出的H更强。这表明无标度脑状态是认知负荷的一个稳健特征，不受所采用的特定神经成像方式的限制。此外，由于fNIRS相对便携且对与运动相关的伪影具有鲁棒性，这些初步结果为在现实生活环境中测量认知负荷的光明未来提供了线索。
