http://nro.sagepub.com/content/19/1/25.abstract
Abstract
In the evolution of the cerebral cortex,
the sophisticated organization in a steady state far away from
thermodynamic equilibrium
has produced the side effect of two fundamental
pathological network events: ictal epileptic activity and spreading
depolarization.
Ictal epileptic activity describes the partial
disruption, and spreading depolarization describes the near-complete
disruption
of the physiological double Gibbs–Donnan steady
state. The occurrence of ictal epileptic activity in patients has been
known
for decades. Recently, unequivocal
electrophysiological evidence has been found in patients that spreading
depolarizations
occur abundantly in stroke and brain trauma. The
authors propose that the ion changes can be taken to estimate relative
changes
in Gibbs free energy from state to state. The
calculations suggest that in transitions from the physiological state to
ictal
epileptic activity to spreading depolarization to
death, the cortex releases Gibbs free energy in a stepwise fashion.
Spreading
depolarization thus appears as a twilight state
close to death. Consistently, electrocorticographic recordings in the
core
of focal ischemia or after cardiac arrest display a
smooth transition from the initial spreading depolarization component
to the later ultraslow negative potential, which is
assumed to reflect processes in cellular death.
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