Impedance Rhythms in Human Limbic System
Abstract
The impedance is a fundamental electrical property of brain tissue, playing a crucial role in shaping the characteristics of local field potentials, the extent of ephaptic coupling, and the volume of tissue activated by externally applied electrical brain stimulation. We tracked brain impedance, sleep–wake behavioral state, and epileptiform activity in five people with epilepsy living in their natural environment using an investigational device. The study identified impedance oscillations that span hours to weeks in the amygdala, hippocampus, and anterior nucleus thalamus. The impedance in these limbic brain regions exhibit multiscale cycles with ultradian (∼1.5–1.7 h), circadian (∼21.6–26.4 h), and infradian (∼20–33 d) periods. The ultradian and circadian period cycles are driven by sleep–wake state transitions between wakefulness, nonrapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Limbic brain tissue impedance reaches a minimum value in NREM sleep, intermediate values in REM sleep, and rises through the day during wakefulness, reaching a maximum in the early evening before sleep onset. Infradian (∼20–33 d) impedance cycles were not associated with a distinct behavioral correlate. Brain tissue impedance is known to strongly depend on the extracellular space (ECS) volume, and the findings reported here are consistent with sleep–wake–dependent ECS volume changes recently observed in the rodent cortex related to the brain glymphatic system. We hypothesize that human limbic brain ECS changes during sleep–wake state transitions underlie the observed multiscale impedance cycles. Impedance is a simple electrophysiological biomarker that could prove useful for tracking ECS dynamics in human health, disease, and therapy.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 24, 2023
- Source ID
- 10.1523/jneurosci.0241-23.2023
Entities
People
- Benjamin H. Brinkmann
- Brian Nils Lundstrom
- Dora Hermes
- Erik K. St. Louis
- Filip Mívalt
- Gregory Worrell
- Irena Balzekas
- Jamie Van Gompel
- Jie Cui
- Jiwon Kim
- Kai J. Miller
- Matthew Stead
- Nicholas M Gregg
- Noelle Nelson
- Paul Croarkin
- Samuel Worrell
- Steven Messina
- Thomas Richner
- Tim Denison
- Vaclav Kremen
- Victoria Marks
- Vladimir Sladky
Organizations
- Mayo Clinic
- National Institute of Neurological Disorders and Stroke