[Eeglablist] Open online discussion: How Do Cable Theory and AMPA/GABA Balance Compare in Their Contributions to 1/f?

[Евгений Машеров]

> Hello Makoto and the 1/f community,
> 
> Inspired by this discussion, I would like to share some empirical data that
> might help quantify the relative contributions of cable theory versus E/I
> balance.
> 
> As a physicist working on materials science and EEG, I conducted an N-of-1
> longitudinal study on a 65-year-old subject (a senior physicist). We
> delivered four consecutive sessions of alpha-tuned rTMS (totaling 8,600
> pulses) within 3.5 hours and monitored the state evolution.
> 
> *Key Findings:*
> 
> 1.
> 
> *Dramatic Exponent Shift:* We observed the 1/f exponent (FOOOF) drifting
> from ~1.2 (baseline) up to ~1.8 at Stage 4.
> 2.
> 
> *Structural Stability vs. Dynamic Change:* Since the subject's neuronal
> morphology (cable theory properties) cannot change by 60% within 3 hours,
> this massive shift provides strong evidence that *E/I balance
> (GABA-mediated inhibition)* is the primary driver of 1/f *dynamics*,
> even if cable theory sets the *baseline*.
> 3.
> 
> *The "Collapse" Threshold:* Our WPLI network analysis shows that while
> the "Small-World" topology optimizes initially, it undergoes a *"Network
> Collapse"* beyond a certain exponent threshold (Stage 5), where global
> efficiency drops and local clustering disintegrates.
> 
> *Implications for the Discussion:* This data supports the idea that
> 1/f-ness is not just a passive physical property but a dynamic biomarker of
> functional boundaries. It also challenges the clinical "more is better"
> approach in TMS therapy, suggesting that we can push the brain into an
> over-inhibited disordered phase.
> 
> These findings are part of a manuscript currently in preparation.
> 
> I look forward to discussing how we might use such longitudinal
> "perturbation" data to weigh the factors Makoto and DeepSeek mentioned.
> 
> Best regards,
> 
> Ching-Ming Lee
> 
> Graduate School of Materials Science
> 
> National Yunlin University of Science and Technology
> 
As a preliminary experiment.
I took EEGs from 167 patients and calculated the 1/f ratio for recordings at rest and during hyperventilation. No statistically significant differences were found (more precisely, for one lead out of 16, a 5% significant difference was found, but this is clearly a multiple comparison effect). The proportion of the spectrum described by the 1/f ratio, however, significantly decreased. This may reflect an increase in artifacts during hyperventilation (motion artifacts, myographic artifacts, etc.).