Table 3.

Studies on the initial dip in fNIRS (years: 2003–2018, source: Web of Science).

Reference	Species	Alert/anesthetic	Stimulation	Area	Detection method
Jasdzewski et al., 2003	Human	Alert	Visual stimulus and finger tapping task	Visual and motor cortex	Time-series visualization
Kato, 2004	Human	Alert	Auditory stimulus	Auditory cortex	Time-series visualization
Akiyama et al., 2006	Human	Alert	Hand grasping task	Motor cortex	Time-series visualization
Akin et al., 2006	Healthy and migraine human patients	Alert	Breadth holding task	Prefrontal cortex	Time-series visualization
Wylie et al., 2009	Human	Alert	Visual stimulus	Visual cortex	Time-series visualization
Lee et al., 2012	Rat	Anesthetic (isoflurane)	Electrical stimulation	Somatosensory cortex	Time-series visualization
Yoshino and Kato, 2012	Human	Alert	Single word listening task	Auditory cortex	Vector-based phase analysis
Sano et al., 2013	Human	Alert	Nasal and mouth breathing task	Prefrontal cortex	Vector-based phase analysis
Dutta et al., 2015	Human stroke survivors	Alert	Anodal tDCS stimulation	Central site Cz	Time-series visualization
Hong and Naseer, 2016	Human	Alert	Mental arithmetic and finger tapping tasks	Prefrontal and motor cortex	Vector phase analysis with a threshold circle
Zafar and Hong, 2017	Human	Alert	Mental arithmetic, mental counting, puzzle solving, finger tapping, finger poking, and visual stimulus tasks	Prefrontal, motor, somatosensory, and visual cortex	Vector phase analysis with a threshold circle
Li et al., 2017	Human	Alert	Left and right hand grasping tasks	Motor cortex	SVM classifier
Khan and Hong, 2017	Human	Alert	Mental arithmetic, mental counting, mental rotation and word generation tasks	Prefrontal cortex	LDA classifier
Mahmoudzadeh et al., 2017	Rat	Anesthetic (urethane)	Forepaw stimulation and French male/female words listening task	Somatosensory and auditory cortex	Time-series visualization
Zafar and Hong, 2018	Human	Alert	Right-hand thumb and little finger tapping	Left motor cortex	Vector phase analysis with dual threshold circles