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Phase lag index: assessment of functional connectivity from multi channel EEG and MEG with diminished bias from common sources
Stam CJ, Nolte G, Daffertshofer A.. Human brain mapping, 2007-11-01
Topic: Risk, prevention and care in population studies
Objective To address the problem of volume conduction and active reference electrodes in the assessment of functional connectivity, we propose a novel measure to quantify phase synchronization, the phase lag index (PLI), and compare its performance to the well-known phase coherence (PC), and to the imaginary component of coherency (IC). Methods The PLI is a measure of the asymmetry of the distribution of phase differences between two signals. The performance of PLI, PC, and IC was examined in (i) a model of 64 globally coupled oscillators, (ii) an EEG with an absence seizure, (iii) an EEG data set of 15 Alzheimer patients and 13 control subjects, and (iv) two MEG data sets. Results PLI and PC were more sensitive than IC to increasing levels of true synchronization in the model. PC and IC were influenced stronger than PLI by spurious correlations because of common sources. All measures detected changes in synchronization during the absence seizure. In contrast to PC, PLI and IC were barely changed by the choice of different montages. PLI and IC were superior to PC in detecting changes in beta band connectivity in AD patients. Finally, PLI and IC revealed a different spatial pattern of functional connectivity in MEG data than PC. Conclusion The PLI performed at least as well as the PC in detecting true changes in synchronization in model and real data but, at the same token and like-wise the IC, it was much less affected by the influence of common sources and active reference electrodes.
Key findings
- Results PLI and PC were more sensitive than IC to increasing levels of true synchronization in the model.
- Finally, PLI and IC revealed a different spatial pattern of functional connectivity in MEG data than PC.
Why it matters
This methods paper introduces the phase lag index for measuring functional connectivity from EEG and MEG and tested it in a small set of 15 Alzheimer patients and 13 controls. It is a technical measurement study and offers no information on treating, curing or preventing Alzheimer's disease.
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Study details
- Evidence strengthLow
How this study scored 54/100
Published in a peer-reviewed journal. Scored zero for study design, sample size, effect reported, studied in people and randomised / blinded because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (Human brain mapping) |
| Journal's citation record | 3 / 4 | Human Brain Mapping: journal h-index 271 (OpenAlex, 2026-10-29) |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 1 / 5 | Rated “low” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 1 / 5 | 2007 — within 20 year(s) of the newest study here |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 7 / 7 | Cited 2,038 times (OpenAlex, 2026-10-10) |
| Citations per year | 5 / 5 | 97.0 citations a year over 21 year(s) since 2007 |
| Impact for its field and year | 4 / 6 | Cited 9.1× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 2 / 6 | Cited by 5 other studies in this library |
| Still being cited | 4 / 4 | Cited 467 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 3 / 4 | Last-listed author Andreas Daffertshofer: h-index 58 (OpenAlex, whole career) |
| Institution's track record | 3 / 3 | National Institutes of Health: institution h-index 2,723 (OpenAlex) |
| Multi-centre collaboration | 2 / 3 | OpenAlex lists 5 institution(s) in 3 countries |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 17266107) |
| Free to read | 0 / 2 | Behind a paywall — scores zero |
| Total | 54 / 100 | — |
What each of these 20 components measures, and what this score is not →
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APA 7th
Stam, C. J., Nolte, G., & Daffertshofer, A. (2007). Phase lag index: assessment of functional connectivity from multi channel EEG and MEG with diminished bias from common sources. Human brain mapping. https://doi.org/10.1002/hbm.20346
Vancouver
Stam CJ, Nolte G, Daffertshofer A. Phase lag index: assessment of functional connectivity from multi channel EEG and MEG with diminished bias from common sources. Human brain mapping. 2007. doi:10.1002/hbm.20346. PMID: 17266107.
BibTeX
@article{stam2007-17266107,
author = {Stam, C. J. and Nolte, G. and Daffertshofer, A.},
title = {{Phase lag index: assessment of functional connectivity from multi channel EEG and MEG with diminished bias from common sources}},
journal = {Human brain mapping},
year = {2007},
doi = {10.1002/hbm.20346},
pmid = {17266107},
url = {https://doi.org/10.1002/hbm.20346}
}
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