发现脑电基础模型在不同队列中对长时程相关性的解码能力差异。
Cross-Cohort Spectral-Temporal Dissociation in Frozen EEG Foundation-Model Representations
- 用五种脑电基础模型提取特征，测试其对α波包络长时程相关性的解码能力。
- 只有CBraMod和BIOT在两个队列中稳定解码非周期性指数，而DFA解码仅在部分队列有效。
- 结果表明模型表征存在谱-时域分离，提示跨队列迁移需谨慎。
目标：检验五个脑电基础模型的冻结表征是否支持对长时程相关性的解码，以α频段振幅包络的去趋势波动分析（DFA）指数为指标。方法：在CAUEEG和BrainLat数据集上评估REVE、LaBraM、BENDR、CBraMod和BIOT。采用统一240秒估计器，8-13 Hz滤波，DFA时间范围2-23.8秒，含伪影掩码与质量控制。固定嵌套交叉验证读出预测DFA及固定模式的非周期性指数。控制实验考察预池顺序敏感性与非周期性残差化。结果：CAUEEG含764个记录，BrainLat含79个。BIOT在CAUEEG中成功解码DFA（R² = 0.232；置信区间0.121–0.310），CBraMod亦呈正向但不精确（R² = 0.121；0.003–0.214），两者在BrainLat均未复现，所有模型点估计均为负。相反，CBraMod与BIOT在两队列中均成功解码非周期性指数（R² = 0.459–0.757）。BIOT在剔除线性非周期关联后仍显著（R² = 0.240）。事后顺序控制显示批次与配置敏感，因原始脑电时段不可交换，该控制仅为描述性而非特异性测试。无修正后的DFA迁移方向通过源标签置换检验。所有五种嵌入可近乎完美区分队列归属，但非纯站点效应。意义：CBraMod与BIOT表现出可重复的模型特异性谱-时域分离——非周期性解码在两队列中一致，而α包络DFA解码具队列依赖性。这些发现界定评估读出的边界，不证明表征缺失或架构原因。迁移与临床关联仍属探索性。
原文摘要 · Abstract (English)
Objective. We tested whether frozen representations from five EEG foundation models support decoding of long-range temporal correlations, measured as the detrended-fluctuation-analysis (DFA) exponent of the alpha-band amplitude envelope. Approach. REVE, LaBraM, BENDR, CBraMod, and BIOT were evaluated in CAUEEG and BrainLat. A common 240 s estimator used 8-13 Hz filtering, DFA over 2-23.8 s, artifact masking, and quality control. One fixed nested-cross-validation readout predicted DFA and a fixed-mode aperiodic exponent. Controls tested pre-pool order sensitivity and aperiodic residualization. Results. CAUEEG included 764 recordings and BrainLat 79. BIOT decoded DFA in CAUEEG (R-squared = 0.232; conditional subject-bootstrap 95 percent interval, 0.121-0.310), and CBraMod was positive but imprecise (R-squared = 0.121; 0.003-0.214). Neither replicated in BrainLat, where all five point estimates were negative. In contrast, CBraMod and BIOT decoded the aperiodic exponent in both cohorts (R-squared = 0.459-0.757). BIOT remained positive after removal of the measured linear aperiodic association in matched CAUEEG data (R-squared = 0.240). The post-hoc order control was batch- and configuration-sensitive. Because chronological EEG epochs are not exchangeable, it was descriptive, not an LRTC-specific test. No revised DFA transfer direction passed source-label permutation testing. Cohort membership was near-ceiling decodable from all five embeddings, but this is not a pure site effect. Significance. CBraMod and BIOT show a replicated, model-specific spectral-temporal dissociation: aperiodic decoding is present in both cohorts, whereas alpha-envelope DFA decoding is cohort-dependent. These findings bound the evaluated readouts; they do not establish representational absence or an architectural cause. Transfer and clinical associations remain exploratory.
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