Table 2.

The details of the main fNIRS studies on people with ASD explained in the present mini-review: only the results of group comparison with matched-controls are shown.

	Age	Model of NIRS machine	Number of channels	Task requirements	Measured regions	Dependent variables	Main analysis of fNIRS data
Kuwabara et al., 2006	6 males and 4 females with PDD (M = 26.5 ± 7.1) 10 TDA (9 males and 1 female; M = 27.9 ± 4.1)	ETG-100	24	Letter fluency task	Frontal lobe	OxyHb DeoxyHb CARS Behavioral Performance	ANOVA with the factors of Group × Hemisphere × Channel
Minagawa-Kawai et al., 2009b	7 boys and 2 girls with low- or high-function ASD (M = 9.2± 1.8) 9 TDC (2 girls and 7 boys; M = 7.3 ± 1.7)	ETG-7000	8	Phonemic discrimination task Prosodic discrimination task	Temporal lobe	Laterality Quotient (LQ) of oxyHb Functional Lateralization (FL) score of oxyHb Behavioral Performance	ANOVA on FL score with the factors of Group × Task
Kawakubo et al., 2009	12 boys and 2 girls with high-functioning autism (M = 12.7± 3.4) 14 TDC (12 boys and 2 girls; M = 10.6 ± 2.8) 9 males and 4 females with high functioning autism (M = 26.7 ± 6.1) 13 TDA (9 males and 4 females; M = 25.8 ± 5.1)	NIRO-200	2	Letter fluency task	Frontal lobe	OxyHb DeoxyHb CARS Behavioral Performance	ANOVA with the factors of Group × Hemisphere for children and adults separately
Kita et al., 2011	10 boys with Asperger Syndrome or high-functioning autism (M = 10.2 ± 1.1) 13 TDC (13 boys; M = 10.9 ± 1.0)	Spectratech OEG-16	16	Self-face recognition	Frontal lobe	OxyHb Eye-movement Self-consciousness scale PARS Behavioral Performance	ANOVA on mean oxyHb values in two ROIs (L-IFG, R-IFG) with the factors of Hemisphere × Group
Iwanami et al., 2011	14 males and 6 females with Asperger syndrome (M = 27.2± 8.5) 18 TDA (12 males and 6 females; M = 31.1 ± 4.7)	ETG-4000	52	Letter and category fluency task	Frontal lobe, Temporal lobe	OxyHb AQ Behavioral Performance	ANOVA on mean oxyHb values in each task with the factors of Group × ROI (left/right temporal, frontal)
Tamura et al., 2012	16 boys and 4 girls with Asperger Syndrome or PDD (M = 10.2 ± 3.4; 6 autistic disorder, 9 Asperger, 5 PDD) 20 TDC (16 boys and 4 girls; M = 9.5 ± 2.5)	NIRO-200	2	Anatomical Imitation (AI) task Mirror-Image Imitation (MI) task	Frontal lobe	Differential value of oxyHb and deoxyHb between AI and MI (AI-MI)	ANOVA on differential oxyHb with the factors of Group × Hemisphere
Xiao et al., 2012	19 boys with high-functioning autism (M = 10.11± 2.08) 16 TDC (16 boys; M = 9.69 ± 1.74)	JH-NIRS-BR-05	16	Go/NoGo task Stroop task	Frontal lobe	OxyHb Behavioral Performance	Group comparison of mean oxyHb in each hemisphere by t-tests
Funabiki et al., 2012	10 males and 1 female with Asperger Syndrome or PDD without language delay (M = 16.8± 6.1) 12 TDC (10 boys and 2 girls; M = 14.2 ± 3.8)	OMM-3000	32	Intentional listening or ignoring tones or stories	Frontal lobe, Temporal lobe	OxyHb DeoxyHb Behavioral Performance	ANOVA on mean oxyHb values in PFC and temporal region with the factors of Group x Hemisphere × Attentional State
Narita et al., 2012	3 males and 8 females with ASD (M = 29.5, range = 14–46) Typically developed people (6 males and 16 females; M = 25.2, range = 19–51)	NIRO-200	2	Visuo-spatial working memory task	Frontal lobe, Temporal lobe	OxyHb Behavioral performance	Comparison of conditional differences in each group
Iwanaga et al., 2013	14 boys and 2 girls with ASD (M = 11.5 ± 1.8) 16TDC (12 boys and 4 girls; M = 11.4 ± 1.8)	ETG-4000	22	Mental State (MS) task Object Characteristics (OC) task	Frontal lobe	OxyHb Behavioral performance	ANOVA on mean oxyHb values in two ROIs (left/right MPFC) with the factors of Group × Hemisphere × Task
Kajiume et al., 2013	6 boys with PDD (M = 10.9 ± 1.6; 3 PDD-NOS, 3 Asperger Syndrome) 6 TDC (6 boys; M = 10.9 ± 1.6)	ETG-100	24	Imitation task Observation task	Frontal lobe, Temporal lobe	OxyHb DeoxyHb Social skill test	Channel-wise Analysis using ANOVA with the factors of Group × Task
Yasumura et al., 2014	7 boys and 4 girls with ASD (M = 10.51± 2.3) 15 TDC (6 boys and 9 girls; M = 28.8 ± 5.5)	ETG-100	24	Stroop task Reverse stroop task	Frontal lobe	OxyHb SNAP questionnaire Behavioral performance	ANOVA on mean oxyHb in each hemisphere with the factors of Hemisphere × Group
Ishii-Takahashi et al., 2014	8 males and 13 females with ASD (M = 30.8 ± 7.2; 5 Asperger Syndrome and 16 PDD-NOS) 21 TDA (13 males and 8 females; M = 28.8 ± 5.5)	ETG-4000	52	VFT SST	Frontal lobe, Temporal lobe	OxyHb Behavioral performance	Channel-wise group comparison of oxyHb Classification of groups by linear discriminant analysis using oxyHb
Jung et al., 2016	8 people with ASD (M = 15.6 ± 9.55) 12 typically developed males (M = 14.5 ± 10.8)	TechEn CW6 fNRIS system	14	1-back task using pictures of Human and robot face	Temporal lobe	OxyHb GARS-2 score	ANOVA with the factors of Group × Hemisphere for human and robot face
	Typical activation pattern	Patients compared to controls	Hemisphere	Regions with group difference	Other Findings
Kuwabara et al., 2006	Significant task-related increase of OxyHb in bilateral PFC	↓	Bilateral	PFC	oxyHb in the right PFC correlated negatively with CARS verbal communication score
Minagawa-Kawai et al., 2009b	Larger FL score in phonemic than in prosody discrimination task	n.s.	n.s.	n.s.	Significantly smaller FL score in children with ASD than in controls in phonemic discrimination task
Kawakubo et al., 2009	OxyHb increase during letter fluency task	↓ in adults	Bilateral	Ventral PFC
Kita et al., 2011	Slight oxyHb increase in typically-developed children, which was significantly smaller than in typically developed adults	n.s.	n.s.	n.s.	OxyHb in R-IFG correlated positively with the level of public self-consciousness and negatively with ASD severity
Iwanami et al., 2011	OxyHb increase during both tasks. The amplitude is larger in letter than category fluency task	↓ in letter fluency task	Bilateral	Frontopolar PFC, DLPFC, VLPFC, and Superior Temporal region
Tamura et al., 2012	Larger differential value of oxyHb in the left than in the right hemisphere	n.s.	n.s.	n.s.	No hemispheric asymmetry was observed in ASD
Xiao et al., 2012	NA	↓ in GoNoGo task	Right	Frontopolar PFC
Funabiki et al., 2012	Larger oxyHb increase in the temporal region when the participants listened to auditory stimuli intentionally	n.s.	n.s.	n.s.	Significant interaction between Hemisphere and Attentional state in story listening in PFC only in ASD group
Narita et al., 2012	Larger oxyHb level during Working Memory (WM) compared to Non-Working Memory (NWM) condition. The overall level of oxyHb level increased as the task load increased	n.s.	n.s.	n.s.	ASD children failed to show clear WM>NWM pattern in oxyHb
Iwanaga et al., 2013	OxyHb increase in bilateral MPFC	↓ in MS task	Bilateral	MPFC
Kajiume et al., 2013	Task-related oxyHb increase	↓ in action observation	Bilateral (mostly in the right)	IFG/PMC
Yasumura et al., 2014	Bilateral oxyHb increase in Reverse stroop task	n.s.	n.s.	n.s.
Ishii-Takahashi et al., 2014	NA	↓ in SST ↓ in VFT	Bilateral Left Left	DLPFC VLPFC, PMA, SMA VLPFC, DLPFC
Jung et al., 2016	Significantly larger increase of oxyHb in the right than left temporal region to human faces. No hemispheric asymmetry was observed to robot faces	n.s.	n.s.	n.s.	ASD children did not show hemispheric asymmetry in oxyHb level to human faces

TDC, Typically Developed Children; TDA, Typically Developed Adults; DLPFC, Dorsolateral Prefrontal Cortex; IFG, Inferior Frontal Gyrus; VLPFC, Ventral Prefrontal Cortex; MTG, Middle Temporal Gyrus; PMA, Primary Motor Area; SMA, Supplementary Motor Area; MPFC, Medial Prefrontal Cortex.