Theory 17/Life, Medicine & Mind /Neurology
Aura Is a Potassium Threshold
Aura is described as cortical spreading depression. What makes a cortex able to sustain it is a separate question.
Migraine aura occurs when extracellular potassium crosses a threshold that sustains spreading depression, so susceptibility is set by potassium buffering capacity rather than by cortical excitability alone.
01The evidence
Spreading depression requires a critical potassium concentration, and susceptibility varies between individuals and regions.
02The tension
Models emphasise excitability and cortical thickness. Buffering capacity is rarely measured, so the threshold is treated as fixed.
03The mechanism
Neurons and glia buffer potassium. When release exceeds buffering, extracellular potassium rises to the level at which spreading depression self-sustains.
That makes buffering the susceptibility variable, and predicts aura should track buffering capacity rather than excitability.
04What this is not
Those models make aura a property of excitation. This makes it a property of buffering.
05Predictions
- P1Aura susceptibility should track buffering capacity.
- P2Buffering enhancers should raise the threshold.
- P3Regions should differ by buffering.
06Refutation
Susceptibility tracking excitability at controlled buffering would favour excitability models.
07What it changes
It would suggest buffering as a target.