title: The Scalp Confounds Near-Infrared Signal from Rat Brain Following Innocuous and Noxious Stimulation.
abstract: Functional near-infrared imaging (fNIRI) is a non-invasive, low-cost and highly portable technique for assessing brain activity and functions. Both clinical and experimental evidence suggest that fNIRI is able to assess brain activity at associated regions during pain processing, indicating a strong possibility of using fNIRI-derived brain activity pattern as a biomarker for pain. However, it remains unclear how, especially in small animals, the scalp influences fNIRI signal in pain processing. Previously, we have shown that the use of a multi-channel system improves the spatial resolution of fNIRI in rats (without the scalp) during pain processing. Our current work is to investigate a scalp effect by comparing with new data from rats with the scalp during innocuous or noxious stimulation (n = 6). Results showed remarkable stimulus-dependent differences between the no-scalp and intact-scalp groups. In conclusion, the scalp confounded the fNIRI signal in pain processing likely via an autonomic mechanism; the scalp effect should be a critical factor in image reconstruction and data interpretation.
authors.affiliation: Departments of Psychology, University of Texas at Arlington, Arlington, TX 76019, USA. jiwei.he@ucsf.edu.|Department of Neurological Surgery, University of California San Francisco, 1700 Owens Street, San Francisco, CA 94158, USA. jiwei.he@ucsf.edu.
authors.forename: Ji-Wei
authors.initials: JW
authors.lastname: He
authors.affiliation: Department of Bioengineering, University of Texas at Arlington, Arlington, TX 76019, USA. hanli@uta.edu.
authors.forename: Hanli
authors.initials: H
authors.lastname: Liu
authors.affiliation: Departments of Psychology, University of Texas at Arlington, Arlington, TX 76019, USA. ypeng@uta.edu.
authors.forename: Yuan Bo
authors.initials: YB
authors.lastname: Peng
keywords: autonomic arousal; deoxygenated hemoglobin; neurovascular coupling; oxygenated hemoglobin; oxygenation; pain; sympathetic; total blood volume change