Multi-centre normative brain mapping of intracranial EEG lifespan patterns in the human brain

TL;DR

This study creates a large-scale, multi-centre normative map of intracranial EEG activity in humans, accounting for age, sex, and hospital effects, to better understand healthy brain function and aid in identifying pathological tissue.

Contribution

It significantly expands sample size and considers hospital, age, and sex effects in normative icEEG mapping, which was limited in prior studies.

Findings

Hospital site significantly affects icEEG maps across all frequency bands.

Age is a more influential predictor of band power than sex.

Age effects vary by frequency band but show no spatial pattern.

Abstract

Background: Understanding healthy human brain function is crucial to identify and map pathological tissue within it. Whilst previous studies have mapped intracranial EEG (icEEG) from non-epileptogenic brain regions, these maps do not consider the effects of age and sex. Further, most existing work on icEEG has often suffered from a small sample size due to the modality's invasive nature. Here, we substantially increase the subject sample size compared to existing literature, to create a multi-centre, normative map of brain activity which additionally considers the effects of age, sex and recording hospital. Methods: Using interictal icEEG recordings from n = 502 subjects originating from 15 centres, we constructed a normative map of non-pathological brain activity by regressing age and sex on relative band power in five frequency bands, whilst accounting for the hospital effect. Results: Recording hospital significantly impacted normative icEEG maps in all frequency bands, and age was a more influential predictor of band power than sex. The age effect varied by frequency band, but no spatial patterns were observed at the region-specific level. Certainty about regression coefficients was also frequency band specific and moderately impacted by sample size. Conclusion: The concept of a normative map is well-established in neuroscience research and particularly relevant to the icEEG modality, which does not allow healthy control baselines. Our key results regarding the hospital site and age effect guide future work utilising normative maps in icEEG.