Table 2.
Selected studies that reported IGF’s relationship with neurochemical factors.
| Author and Year | Sample | Methods | IGF Measure | Relevant Findings |
|---|---|---|---|---|
| Robson et al., 2015 [22] | 34 healthy adults | MEG, MRS, visual gratings | Power | IGF: 52.5 ± 4.4 Hz, ~45–65 Hz. No correlation of IGF with V1 surface area and thickness. Positive correlation of IGF with V1 GABA (R = 0.34), but insignificant after including age as a covariate |
| Wyss et al., 2017 [24] | 15 healthy adults | EEG, MRS, auditory stimulation | Power | IGF: ~30–160 Hz. No correlation of IGF with GABA and glutamate |
| Chen et al., 2014 [29] | 12 adults with schizophrenia; 12 healthy adults | EEG, MRS, working memory assessment | Amplitude | IGF: ~30–50 Hz. Positive correlation of IGF with DLPFC GABA (r = 0.58) |
| Lally et al., 2014 [30] | 14 healthy adults | EEG, MRI, categorization task | Power | Negative correlation of IGF with glutamate concentration in the occipital cortex (r = −0.54) |
| Morgan et al., 2008 [38] | Wistar rats | In vitro LFP, arachidonylcyclopropylamide (ACPA) and LY320135 |
Power | In hippocampal entorhinal cortex slices, IGF pre-injection: 40.7 ± 2.4 Hz; IGF after CB1R agonist (ACPA) injection decreased to 35.6 ± 1.8 Hz, but returned to 41.2 ± 1.8 Hz after CB1R antagonist (LY320135) injection |
| Pálhalmi et al., 2004 [39] | Wistar rats | In vitro LFP, carbachol and (RS)-3,5-dihydroxyphenylglycine (DHPG) | Power | IGF post-carbachol: 31.5 ± 0.7 Hz; IGF post-DHPG: 41.2 ± 0.6 Hz. Positive correlation of IGF with DHPG dosage |
| Shaw et al., 2013 [51] | 37 healthy adults: 19 remitted depression (RD), 18 never depressed (ND) |
MEG, MRS, visual gratings | Power | IGF in RD: 57.64 Hz, IGF in ND: 55.83 Hz, non-significant difference. No correlation of IGF with occipital GABA |
| Edden et al., 2009 [57] | 13 healthy adults | MEG, MRS, visual gratings | Amplitude | IGF: 50.9 ± 1.3 Hz, 43.5–58.0 Hz. Positive correlation of IGF with V1 GABA concentration (r = 0.67) |
| Muthukumaraswamy et al., 2009 [58] | 12 healthy adults | MEG, MRS, fMRI, visual gratings | Amplitude | IGF: 40–66 Hz. Positive correlation of IGF with V1 GABA concentration (R = 0.68) |
| Gaetz et al., 2011 [59] | 9 healthy adults | MEG, MRI, MRS, visual stimuli and motor responses | Amplitude | IGF: ~70–80 Hz. Positive correlation of IGF with M1 GABA concentration: R2 = 0.46 (3.9 Hz increase per 0.1 GABA increase) |
| Cousijn et al., 2014 [60] | 50 healthy adults | MEG, MRS, visual gratings | Power | IGF: ~40–75 Hz. No correlation of IGF with occipital GABA and glutamate |
| Kujala et al., 2015 [61] | 13 healthy adults | MEG, PET, MRI, working memory assessment | Amplitude | IGF: ~40–100 Hz. Positive correlation of IGF with GABAA receptor density in V1 (rho = 0.74) |
| Campbell et al., 2014 [62] | 16 healthy adults | MEG, alcohol, visual gratings, finger movement task | Amplitude | IGF pre-alcohol: ~55 Hz; IGF post-alcohol: ~50 Hz. Drug and time interaction for visual IGF, where IGF decreased after alcohol administration |
| Shaw et al., 2015 [63] | 20 healthy adults | MEG, MRI, visual gratings, ketamine | Amplitude | For high contrast gratings, IGF pre-ketamine: ~51 Hz; IGF post-ketamine: ~49 Hz |
| Lozano-Soldevilla et al., 2014 [64] | 32 healthy adults | MEG, lorazepam, working memory assessment | Power | IGF pre-lorazepam: >75 Hz; IGF post-lorazepam: <75 Hz |
| Magazzini et al., 2018 [65] | 15 healthy adults | MEG, tiagabine, visual gratings | Power | IGF after placebo: ~53 Hz; IGF after tiagabine: ~50 Hz |
| Kocsis et al., 2014 [66] | Rats | In vivo LFP, D4 receptor agonist A-412997 (Tocris) injections | Power | IGF pre-injection: 51 ± 1 Hz; IGF post-injection: 46 ± 2 Hz |
| Kühn et al., 2017 [67] | 42 Wistar rats | In vivo LFP, levodopa or apomorphine injections, behavioral testing | Power | IGF decreased with apomorphine dosage from ~65 Hz to ~60 Hz in Parkinson’s disease animal model and controls; IGF increased with levodopa dosage from ~60 Hz to ~65 Hz, only in controls |
| Craig and McBrain 2015 [68] | Nkx2–1-cre:RCE and Htr3a-GFP mice. | In vitro LFP, kainate | Power | Kainate evoked gamma in hippocampal slices. IGF in CA3 region: 52 ± 1.2 Hz, ~40–65 Hz; IGF in CA1 region: 63 ± 0.87 Hz, ~40–80 Hz |
Abbreviations: ACPA—arachidonylcyclopropylamide; DHPG—(RS)-3,5-dihydroxyphenylglycine; DLPFC—dorsolateral prefrontal cortex; EEG—electroencephalogram; fMRI—functional magnetic resonance imaging; IGF—individual gamma frequency; LFP—local field potential; MEG—magnetoencephalogram; MRI—magnetic resonance imaging; MRS—magnetic resonance spectroscopy; PET—positron emission tomography.