Distinctive ionic transport of freshly excised human epileptogenic brain tissue

David Emin; Aria Fallah; Noriko Salamon; Gary Mathern; Massoud Akhtari

doi:10.1063/5.0077825

Distinctive ionic transport of freshly excised human epileptogenic brain tissue

Appl Phys Lett. 2021 Dec 20;119(25):253701. doi: 10.1063/5.0077825.

Authors

David Emin¹, Aria Fallah², Noriko Salamon³, Gary Mathern², Massoud Akhtari⁴

Affiliations

¹ Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, USA.
² Department of Neurosurgery and Pediatrics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
³ Department of Radiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.
⁴ Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.

Abstract

Epileptogenic lesions have higher concentrations of sodium than does normal brain tissue. Such lesions are palpably recognized by a surgeon and then excised in order to eliminate epileptic seizures with their associated abnormal electrical behavior. Here, we study the frequency-dependent electrical conductivities of lesion-laden tissues excised from the brains of epilepsy patients. The low-frequency (<1000 Hz) conductivity of biological tissue primarily probes extracellular solvated sodium-cations traveling parallel to membranes within regions bounded by blockages. This conductivity rises monotonically toward saturation as the frequency surpasses the rate with which diffusing solvated sodium cations encounter blockages. We find that saturation occurs at dramatically higher frequencies in excised brain tissue containing epileptogenic lesions than it does in normal brain tissue. By contrast, such an effect is not reported for tumors embedded in other excised biological tissue. All told, epileptogenic lesions generate frequency-dependent conductivities that differ qualitatively from those of both normal brain tissues and tumors.