Table 3.
Studies using functional connectivity.
| Paper | Patients characteristics | Controls characteristics | Condition | Measure | Changes in ASD |
|---|---|---|---|---|---|
| Orekhova et al. (32, 33) | n = 28; mean age = 14.4 months; sex = 18 F, 10 M; HR | n = 10; mean age = 38 months; sex = 3 F, 7 M; High-risk ASD (HR-ASD) | 3 video stimuli | De-biased weighted phase lag index | HR-ASD: hyper-connectivity in alpha band in frontal and central areas (p < 0.05) |
| n = 26; mean age = 14.7 months; sex = 14 F, 12 M; Low-risk (LR) | n = 18; mean age = 38 months; sex = 15 F, 3 M; High-risk non-ASD | The degree of hyper-connectivity correlated with the severity of ASD symptoms in later diagnosed | |||
| Righi et al. (34) | n = not specified; adults HR of ASD Had an older sibling with ASD | n = not specified; adults LR of ASD | Speech sounds | Coherence | Infants at risk: reduced connectivity (p < 0.005) |
| Connectivity: HR-ASD < HR-NASD < LR | |||||
| Barttfeld et al. (35) | n = 10; mean age = 23.8 years; sex = 1 F, 9 M; subtypes = autism, Asperger syndrome | n = 10; mean age = 25.3 years; sex = 1 F, 9 M | Relaxed eyes closed | Coherence (synchronization likelihood) | Delta band: decreased long-range connectivity (fronto-occipital) and increased short-range connectivity (frontal lateral) in ASD (p < 0.05) |
| Murias et al. (36) | n = 18; adults sex = 18 M diagnosis = ASD; Some were taking medication | n = 18; age-matched sex = 18 M | Relaxed eyes closed | Coherence | Theta: increased connectivity in frontal and temporal left hemisphere (p < 0.025) |
| Alpha: decreased long-range connections of the frontal area (p < 0.025) | |||||
| Leveille et al. (37) | n = 9; mean age = 21.1 years; diagnosis = ASD | n = 13; mean age = 21.5 years | Rapid eye movement (REM) sleep | Coherence | Theta and delta: increased long-range coherence between the occipital region and the rest of the brain and decreased the frontal area (p < 0.05) |
| Boersma et al. (38) | n = 12; mean age = 3.5 years; sex = 2 F, 10 M; subtypes = autism (2), Asperger syndrome (1), PDD-NOS (9); average IQ = 85 | n = 19; mean age = 3.5 years; sex = 19 M; average IQ = 108 | Pictures of cars | Clustering | Overall whole brain under-connectivity in beta, theta, and alpha bands (p < 0.01) |
| Catarino et al. (13, 39) | n = 15; mean age = 31 months; diagnosis = ASD | n = 15; mean age = 29 months | Object recognition | Coherence | Decreased coherence for both tasks in alpha and theta bands (p < 0.05) |
| Carson et al. (40) | n = 19; mean age = 9.9 years; sex = 1 F, 19 M; diagnosis = ASD | n = 13; mean age = 10 years; sex = 4 F, 9 M | Videos of someone reading a story | Coherence | Decreased coherence in alpha band in frontal and temporal lobes at baseline (p < 0.05) |
| Cantor et al. (41) | n = 11; age range = 4–12 years; sex = 2 F, 9 M; subtypes = autism | n = 119; classification = normal children (n = 88, age range = 5–15 years), a matched group of intellectually disabled children (n = 18, age range = 5–15 years) and a group of mentally age-matched normal toddlers (n = 13, age range = 16 months to 5 years) | Relaxed eyes open | Coherence | Higher coherence between and within hemispheres in delta and alpha bands (p < 0.05) |
| Chan et al. (42, 43) | n = 21; mean age = 10.27 years; sex = 2 F, 19 M | n = 21; mean age = 9.85 years; sex = 7 F, 14 M | Object recognition | Coherence | Increased frontal coherence in left hemisphere in theta bands (p < 0.05) |
| Coben et al. (44) | n = 20; mean age = 6–11 years; sex = 6 F, 14 M | n = 20; mean age = 6–11 years; sex = 6 F, 14 M | Relaxed eyes close | Coherence | Decreased coherence in theta and delta bands in frontal region (p < 0.005), delta, theta, and alpha in temporal region (p < 0.05) and delta, theta, and beta in parietal and occipital regions (p < 0.05) |
| Buckley et al. (45) | n = 87; age range = 2–6 years; diagnostic = ASD | n = 29; age range = 2–6 years (TYP) | Awake, slow-wave sleep, and REM sleep | Coherence, phase lag, | Increased coherence observed in ASD compared to TYP, almost exclusively during slow-wave sleep, in the frontal–parietal areas, in long-distance pairs |
| n = 21; age range = 2–6 years; diagnosis = developmental delay without ASD (DD) | |||||
| Lazarev et al. (46) | n = 14; age range = 6–14 years; sex = 14 M; diagnosis = ASD | n = 19; age range = 6–14 years; sex = 19 M | Intermittent photic stimulation | Coherence | Significantly lower coherence in ASD than the control group in the beta frequencies |
n, number of subjects; F, female; M, male; PDD-NOS, pervasive developmental disorder-not otherwise specified; REM, rapid eye movement; ASD, autism spectrum disorders; HR-ASD, High-risk ASD; HR, high-risk.