Electric field effects in hyperexcitable neural tissue: a review

Area of Science:

• Neuroscience
• Computational Neuroscience
• Biophysics

Background:

• Uniform electric fields modulate neuronal excitability, typically with a threshold around 1 mV mm(-1) under normal physiological conditions.
• Field sensitivity may increase in pathological conditions like epilepsy, potentially lowering the effective threshold.

Purpose of the Study:

• To investigate the threshold for electric field-induced neuronal blockade in simulated epilepsy conditions.
• To determine if extracellular resistance, modulated by osmolarity, affects the efficacy of electric fields on neural tissue.

Main Methods:

• Application of uniform electrical fields to hippocampal brain slices.
• Exposure of slices to picrotoxin, high potassium, or low calcium solutions to simulate pathological conditions.
• Manipulation of extracellular solution osmolarity to assess its impact on field efficacy.

Main Results:

• In low calcium conditions, 10% of slices showed complete neuronal activity blockade at 1 mV mm(-1), indicating a threshold below this value.
• Decreasing extracellular osmolarity by 10% reduced the minimum required field by 56%, while a 14% increase raised it by 81%.
• Extracellular volume significantly modulates electric field efficacy and can lower threshold amplitudes.

Conclusions:

• The threshold for electric field-induced neuronal suppression is lower than 1 mV mm(-1) in low calcium conditions.
• Extracellular osmolarity and volume are critical factors influencing the sensitivity of neural tissue to applied electric fields.
• These findings have implications for understanding neuromodulation and developing targeted electrical stimulation therapies.