Table 4.
Selected studies that reported IGF’s relationship with brain states.
| Author and Year | Sample | Methods | IGF Measure | Relevant Findings |
|---|---|---|---|---|
| Baltus et al., 2018 [4] | 26 healthy adults | EEG, tACS, auditory steady-state stimulation, gap detection task | Amplitude | IGF: 49 Hz, ~37–63. In IGF + 4 Hz stimulation group, IGF increased after tACS; in IGF-4 Hz group, IGF decreased after tACS |
| Lozano-Montes et al., 2020 [34] | 29 Long Evans rats | In vivo LFP, optical stimulation, deep brain stimulation, behavioral tests | Power | IGF during quiet wakefulness: ~53 Hz, ~50–58 Hz; IGF during self-grooming: ~50 Hz, ~45–53 Hz |
| Munglani et al. 1993 [78] | 7 healthy adults | EEG, isoflurane, auditory click stimulation, cognitive tests | Power | IGF awake: 32.8 Hz, 28–41 Hz. IGF anesthetized: 24.8 Hz, 21.5–30.6 Hz |
| Andrade et al. 1996 [79] | 12 healthy adults | EEG, propofol, auditory click stimulation, cognitive assessment | Power | IGF: 37.6 Hz, 33.5–41.5 Hz. IGF in light sedation: 29.9 Hz, 23.5–35.5 Hz; IGF in deep sedation: 27.1 Hz, 20.5–35.5 Hz |
| Xing et al., 2012 [80] | 2 monkeys | In vivo LFP, anesthesia, visual gratings | Amplitude | IGF in awake: 60 ± 9 Hz, ~55–64 Hz; IGF in anesthetized: 40 ± 8.8 Hz, ~35–42 Hz |
| Saxena et al., 2013 [81] | 15 healthy adults | MEG, propofol, visual gratings | Amplitude | IGF: ~57 Hz. No difference in IGF between awake and sedated states |
| Sumner et al., 2018 [82] | 20 healthy female adults | EEG, blood tests, visual gratings | Power | IGF depends on menstrual phase. For moving stimuli, IGF in luteal phase: 63.42 ± 5.3 Hz; IGF in follicular phase: 59.86 ± 7.19 Hz. For stationary stimuli, IGF in luteal phase: 58.16 ± 3.95 Hz; IGF in follicular phase 52.41 ± 3 Hz. No correlations between IGF and hormone levels |
| Baltus et al., 2020 [83] | 16 healthy adults | EEG, tACS, auditory steady-state stimulation, gap detection task | Amplitude | IGF: ~35–60 Hz. Negative correlation of IGF with gap detection threshold (rho = −0.6). Positive correlation of IGF with change in performance after tACS in the experimental group (rho = 0.81), but not in the control group |
| Rufener et al., 2022 [84] | 30 children with developmental dyslexia (DD) |
EEG, tACS, auditory steady-state stimulation, language assessment | Power | Before tACS application, IGF in tACS group: 40.28 ± 6.22 Hz; IGF in controls: 41.07 ± 6.04 Hz. Immediate effects, ΔIGF in tACS group: 3.38 ± 1.89 Hz; ΔIGF in controls: 1.08 ± 1.85 Hz. Long-term effects, ΔIGF in tACS group: 3.91 ± 1.48 Hz; ΔIGF in controls: −1.58 ± 1.13 Hz |
| Dawood et al., 2022 [85] | 49 healthy adults | EEG, tDCS, checkerboard visual stimulus | Power | No difference in IGF between pre- and post-tDCS |
| Wilson et al., 2017 [87] | 35 healthy adults | MEG, MRI, tDCS, visual gratings | Amplitude | tDCS did not modulate IGF |
| Lewine et al., 2019 [88] | 8 healthy adults | EEG, auditory stimulation, non-invasive vagal nerve stimulation | Power | Baseline IGF at Oz electrode: 44–49 Hz. IGF post-stimulation decreased by 3–4 Hz |
Abbreviations: EEG—electroencephalogram; IGF—individual gamma frequency; LFP—local field potential; MEG—magnetoencephalogram; MRI—magnetic resonance imaging; tACS—transcranial alternating current stimulation; tDCS—transcranial direct current stimulation.