Understanding the sodium cation conductivity of human epileptic brain tissue
| Autor: | Andrew Frew, William H. Yong, Massoud Akhtari, David Emin, Gary W. Mathern, Aria Fallah, Noriko Salamon |
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| Rok vydání: | 2021 |
| Předmět: |
Sodium
QC1-999 SODIUM CATION General Physics and Astronomy chemistry.chemical_element 02 engineering and technology Trapping Brain tissue Optical Physics Conductivity Neurodegenerative 01 natural sciences Ion Nuclear magnetic resonance 0103 physical sciences Electrical and Electronic Engineering 010302 applied physics Quantum Physics Epilepsy Chemistry Physics Neurosciences 021001 nanoscience & nanotechnology Brain Disorders Neurological Charge carrier 0210 nano-technology Carrier dynamics Regular Articles |
| Zdroj: | AIP advances, vol 11, iss 4 AIP Advances, Vol 11, Iss 4, Pp 045118-045118-5 (2021) AIP Advances |
| Popis: | Transient and frequency-dependent conductivity measurements on excised brain-tissue lesions from epilepsy patients indicate that sodium cations are the predominant charge carriers. The transient conductivity ultimately vanishes as ions encounter blockages. The initial and final values of the transient conductivity correspond to the high-frequency and low-frequency limits of the frequency-dependent conductivity, respectively. Carrier dynamics determines the conductivity between these limits. Typically, the conductivity rises monotonically with increasing frequency. By contrast, when pathology examinations found exceptionally disorganized excised tissue, the conductivity falls with increasing frequency as it approaches its high-frequency limit. To analyze these measurements, excised tissues are modeled as mixtures of “normal” tissue within which sodium cations can diffuse and “abnormal” tissue within which sodium cations are trapped. The decrease in the conductivity with increasing frequency indicates the predominance of trapping. The high-frequency conductivity decreases as the rate with which carriers are liberated from traps decreases. A relatively low conductivity results when most sodium cations remain trapped in “abnormal” brain tissue, while few move within “normal” brain tissue. Thus, the high densities of sodium nuclei observed by 23Na-MRI in epilepsy patients’ lesions are consistent with the low densities of diffusing sodium cations inferred from conductivity measurements of excised lesions. |
| Databáze: | OpenAIRE |
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