Background
EEG coherence — the synchronization of electrical activity between brain regions — is a marker of functional connectivity and is reduced in conditions affecting cognitive processing, including cerebrovascular disease, dementia, and post-stroke recovery. Semax had shown neuroprotective effects in ischemic stroke models, but its effects on brain functional connectivity in human patients with cerebrovascular disease had not been characterized.
This study from the Institute of Normal Physiology, Russian Academy of Medical Sciences, used quantitative EEG to objectively assess Semax’s effects on brain electrical organization in a clinically relevant patient population.
Methods
40 patients with confirmed cerebrovascular disease (chronic ischemic encephalopathy grades I–II) were randomized to:
- Semax 400–600 µg/day intranasal for 10 days
- Placebo
Assessments before and after treatment:
- Quantitative EEG: coherence analysis across all electrode pairs (alpha 8–13 Hz, theta 4–8 Hz, beta 13–30 Hz)
- Neuropsychological: Attention Network Test (ANT), Digit Span (working memory), Trail Making Test (executive function)
Key Findings
EEG Coherence Changes (Semax vs. Placebo):
- Alpha-band coherence significantly increased between frontal and occipital/parietal regions (+18% from baseline, p < 0.01)
- Theta-band coherence enhanced in fronto-temporal networks (+12%, p < 0.05)
- Beta-band changes were not statistically significant
Cognitive Performance:
| Test | Semax Group | Placebo Group |
|---|---|---|
| Digit Span | Improved (p < 0.05) | No change |
| Trail Making A | Faster (p < 0.05) | No change |
| ANT (executive control) | Improved (p < 0.05) | No change |
| Long-term memory recall | Trend, not significant | No change |
Correlation Analysis:
- The degree of alpha coherence increase correlated significantly with cognitive performance improvements (r = 0.61, p < 0.01)
- Suggests EEG coherence is a meaningful biomarker for Semax’s cognitive effects
Clinical Significance
EEG coherence improvements after Semax provide objective neurophysiological evidence of functional brain enhancement — not just subjective cognitive reports. This is important because:
- Biomarker validation: If alpha coherence reliably predicts cognitive benefit, it could serve as a Semax response biomarker in future trials
- Cerebrovascular indication: The patient population (chronic ischemic encephalopathy) represents a high-prevalence group with substantial cognitive burden and few effective treatments
- Mechanism alignment: Enhanced fronto-posterior connectivity is consistent with BDNF-mediated improvements in hippocampal-cortical communication (see Dolotov 2006)
Limitations
- Small sample (n = 40); limited statistical power for subgroup analyses
- 10-day treatment; durability of EEG and cognitive changes after Semax discontinuation was not assessed
- EEG coherence changes are a surrogate — direct neuronal/synaptic mechanisms were not measured
- Single Russian center; replication in Western clinical trials is needed
- Cerebrovascular disease severity was not fully standardized across patients