EEG Microstate Rigidity Tracks Depression in Temporal Lobe Epilepsy

By Tom Whitfield

A resting-state scalp EEG study of 26 individuals with unilateral temporal lobe epilepsy has found that depressive symptom severity correlates with how long the brain stays locked in an ictal-hemisphere-aligned microstate. The correlation reached r=0.57 (p=0.002) between dwell time in that microstate and Beck Depression Inventory-II scores. The paper appeared in Epilepsy & Behavior in November 2026 (DOI: 10.1016/j.yebeh.2026.111205), with Brian Jung as senior author and Diego Pizzagalli and Beth Lopour among the collaborators.

The study analyzed visually normal resting-state scalp EEG, not ictal recordings. The investigators clustered global field power peaks into four canonical microstate classes. Because patients had epilepsy of differing lateralities, they mirrored electrode positions to align the ictal hemisphere across all subjects.

The team quantified four metrics for each microstate: dwell time, fractional occupancy, global transition entropy, and Markov transition probabilities. They then related each measure to BDI-II scores across the cohort.

What separated the high-depression group?

Patients with BDI scores of 13 or higher (N=12) showed longer mean dwell time in the ictal hemisphere-aligned microstate than patients below that threshold (N=14). The high-symptom group also showed reduced global transition entropy (p=0.02), a measure of how flexibly the brain moves between microstates. Entropy correlated inversely with symptom severity (r=-0.54, p=0.004).

The occupancy picture carried a finer distinction. Fractional occupancy of the ictal-aligned microstate was similar between the two groups. What differed was the path into it. High-symptom patients were less likely to transition into the ictal-aligned microstate from non-ictal or posterior configurations. Once engaged, however, that state persisted longer, indicating prolonged stabilization of the network configuration.

The takeaway in plain words: dynamics, not the static topography of brain states, tracked depression in these patients.

Why this matters for the reading room

Depressive symptoms are a common and disabling comorbidity in temporal lobe epilepsy, yet the neural mechanisms connecting seizure networks to affective symptoms have remained unclear. Limbic network dysfunction has been implicated in both conditions, but prior work had not established whether time-varying dynamics of large-scale electrophysiological states reflect depressive severity in TLE.

This study addresses that gap with routine scalp EEG of the kind already collected in epilepsy monitoring units. The investigators note that higher depressive burden associated with increased temporal rigidity of the ictal-aligned microstate reflects impaired disengagement of epileptogenic network configurations. In practice, quantitative microstate metrics computed from visually normal interictal EEG could offer a biomarker dimension that standard visual review does not capture.

The finding is investigative, not diagnostic. The cohort numbered 26 patients at a single center, and the design demonstrates association, not causation, between microstate rigidity and depressive symptoms.

The authors conclude that depressive symptoms in TLE may relate to epilepsy-driven disruptions in large-scale neural dynamics, and future work with larger longitudinal cohorts will need to test whether these microstate measures can stratify patients before mood disorders become clinically disabling.