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Neuroimage. 2015 Oct 15;120:394-9. doi: 10.1016/j.neuroimage.2015.07.019. Epub 2015 Jul 11.

Simultaneous epidural functional near-infrared spectroscopy and cortical electrophysiology as a tool for studying local neurovascular coupling in primates.

Author information

1
Max Planck Institute for Biological Cybernetics, Tübingen, Germany; Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany. Electronic address: azaidi@tue.mpg.de.
2
Max Planck Institute for Biological Cybernetics, Tübingen, Germany; Systems Neurophysiology, Fachbereich Biologie, Technische Universität Darmstadt, Germany.
3
Max Planck Institute for Biological Cybernetics, Tübingen, Germany; Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany.
4
Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
5
Department of Physiology and Biophysics and Washington National Primate Research Center, University of WA, Seattle, USA.
6
Max Planck Institute for Biological Cybernetics, Tübingen, Germany; Center for Imaging Sciences, Biomedical Imaging Institute, University of Manchester, UK.
7
Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany; Ospedale San Camillo, Istituto di Ricovero e Cura a Carattere Scientifico, Venezia-Lido, Italy; Department of Psychology, Biological Psychology, Universidad de las lslas Baleares, Spain.
8
Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany; Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA. Electronic address: ranganatha.sitaram@bme.ufl.edu.

Abstract

Simultaneous measurements of intra-cortical electrophysiology and hemodynamic signals in primates are essential for relating human neuroimaging studies with intra-cortical electrophysiology in monkeys. Previously, technically challenging and resourcefully demanding techniques such as fMRI and intrinsic-signal optical imaging have been used for such studies. Functional near-infrared spectroscopy is a relatively less cumbersome neuroimaging method that uses near-infrared light to detect small changes in concentrations of oxy-hemoglobin (HbO), deoxy-hemoglobin (HbR) and total hemoglobin (HbT) in a volume of tissue with high specificity and temporal resolution. FNIRS is thus a good candidate for hemodynamic measurements in primates to acquire local hemodynamic signals during electrophysiological recordings. To test the feasibility of using epidural fNIRS with concomitant extracellular electrophysiology, we recorded neuronal and hemodynamic activity from the primary visual cortex of two anesthetized monkeys during visual stimulation. We recorded fNIRS epidurally, using one emitter and two detectors. We performed simultaneous cortical electrophysiology using tetrodes placed between the fNIRS sensors. We observed robust and reliable responses to the visual stimulation in both [HbO] and [HbR] signals, and quantified the signal-to-noise ratio of the epidurally measured signals. We also observed a positive correlation between stimulus-induced modulation of [HbO] and [HbR] signals and strength of neural modulation. Briefly, our results show that epidural fNIRS detects single-trial responses to visual stimuli on a trial-by-trial basis, and when coupled with cortical electrophysiology, is a promising tool for studying local hemodynamic signals and neurovascular coupling.

[Indexed for MEDLINE]

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