title: PHASE DIFFERENCE BETWEEN LOW-FREQUENCY OSCILLATIONS OF CEREBRAL DEOXY- AND OXY-HEMOGLOBIN CONCENTRATIONS DURING A MENTAL TASK.
abstract: Hemodynamic low-frequency (~0.1 Hz) spontaneous oscillations as detected in the brain by near-infrared spectroscopy have potential applications in the study of brain activation, cerebral autoregulation, and functional connectivity. In this work, we have investigated the phase lag between oscillations of cerebral deoxy- and oxy-hemoglobin concentrations in the frequency range 0.05-0.10 Hz in a human subject during a mental workload task. We have obtained a measure of such phase lag using two different methods: (1) phase synchronization analysis as used in the theory of chaotic oscillators and (2) a novel cross-correlation phasor approach. The two methods yielded comparable initial results of a larger phase lag between low-frequency oscillations of deoxy- and oxy-hemoglobin concentrations during mental workload with respect to a control, rest condition.
authors.affiliation: Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
authors.forename: Angelo
authors.initials: A
authors.lastname: Sassaroli
authors.forename: Feng
authors.initials: F
authors.lastname: Zheng
authors.forename: Michele
authors.initials: M
authors.lastname: Pierro
authors.forename: Peter R
authors.initials: PR
authors.lastname: Bergethon
authors.forename: Sergio
authors.initials: S
authors.lastname: Fantini