title: Reduction of Delay in Detecting Initial Dips from Functional Near-Infrared Spectroscopy Signals Using Vector-Based Phase Analysis.
abstract: In this paper, we present a systematic method to reduce the time lag in detecting initial dips using a vector-based phase diagram and an autoregressive moving average with exogenous signals (ARMAX) model-based q-step-ahead prediction algorithm. With functional near-infrared spectroscopy (fNIRS), signals related to mental arithmetic and right-hand clenching are acquired from the prefrontal and left primary motor cortices, respectively. The interrelationship between oxygenated hemoglobin, deoxygenated hemoglobin, total hemoglobin and cerebral oxygen exchange are related to initial dips. Specifically, a threshold value from the resting state hemodynamics is incorporated, as a decision criterion, into the vector-based phase diagram to determine the occurrence of initial dips. To further reduce the time lag, a [Formula: see text]-step-ahead prediction method is applied to predict the occurrence of the dips. A combination of the threshold criterion and the prediction method resulted in the delay time of about 0.9[Formula: see text]s. The results demonstrate that rapid detection of initial dip is possible and therefore can be used for real-time brain-computer interfacing.
authors.affiliation: 1 School of Mechanical Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 46241, Korea.
authors.forename: Keum-Shik
authors.initials: KS
authors.lastname: Hong
authors.affiliation: 2 Department of Cogno-Mechatronics Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 46241, Korea.
authors.forename: Noman
authors.initials: N
authors.lastname: Naseer
mesh_terms: D000465:Algorithms; D002560:Cerebrovascular Circulation / Q000502:physiology; D059907:Functional Neuroimaging / Q000379:methods*; D006225:Hand / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D055641:Mathematical Concepts; D009043:Motor Activity / Q000502:physiology; D009044:Motor Cortex / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D017397:Prefrontal Cortex / Q000502:physiology*; D011340:Problem Solving / Q000502:physiology; D012146:Rest; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013997:Time Factors
chemical_list: D010100:Oxygen
keywords: Initial dip; functional near-infrared spectroscopy; motor cortex; prefrontal cortex; reduction of detection time; vector-based phase analysis