Diminished circadian and ultradian rhythms of human brain activity in pathological tissue in vivo

TL;DR

This study reveals that pathological brain tissue in humans exhibits persistently diminished circadian and ultradian rhythms, regardless of regional differences or pathological events, highlighting potential targets for therapeutic intervention.

Contribution

It provides the first in vivo evidence that brain pathology is associated with sustained reduction in biological rhythms across different regions and conditions.

Findings

Diminished circadian and ultradian rhythms in pathological tissue

Rhythmic reductions are persistent over time

Findings are independent of regional variation or pathological events

Abstract

Chronobiological rhythms, such as the circadian rhythm, have long been linked to neurological disorders, but it is currently unknown how pathological processes affect the expression of biological rhythms in the brain. Here, we use the unique opportunity of long-term, continuous intracranially recorded EEG from 38 patients (totalling 6338 hours) to delineate circadian (daily) and ultradian (minute to hourly) rhythms in different brain regions. We show that functional circadian and ultradian rhythms are diminished in pathological tissue, independent of regional variations. We further demonstrate that these diminished rhythms are persistent in time, regardless of load or occurrence of pathological events. These findings provide evidence that brain pathology is functionally associated with persistently diminished chronobiological rhythms in vivo in humans, independent of regional variations or pathological events. Future work interacting with, and restoring, these modulatory chronobiological rhythms may allow for novel therapies.