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Study identifies useful markers of brain excitability that could track medication effect

Recent analysis of human electrocorticogram data show a link between order in neuron activity and excitability in the brain, which could foster less invasive, and thus more versatile, monitoring of treatment for conditions such as epilepsy.

“Changes in cortical excitability are believed to play a role in normal conditions during the course of wake and sleep. A perturbational approach to study excitability in human cortex found increased responses after a period of sustained wakefulness that were rebalanced after sleep. Such findings suggest that excitability could increase during wake, which might result in suboptimal information processing in cortical networks and point to a pivotal role of sleep in rebalancing the level of excitability,” Christian Meisel, MD, of the NIMH, and colleagues wrote.

Researchers analyzed two datasets of human electrocorticogram data. The first included two patients where regularly recurring electrical stimuli had been applied over at least a day while stimulation responses and activity in between stimulations were recorded. The second included 10 patients with multiday recordings of ongoing activity under varying levels of antiepileptic drugs.

Researchers observed a correlation between brain network order and network excitability. Brain networks of patients who stopped antiepileptic treatment were at the threshold between disorder and order.

As antiepileptic treatment was increased, brain networks became less disordered.

These results indicate that excitability in epileptic networks is effectively reduced by antiepileptic drugs, suggesting global levels of phase synchronization may be useful in quantifying excitability for routine clinical conditions, according to researchers.

“Our main finding is that these measures [intrinsic excitability measures based on

ongoing activity without the need of external perturbations] correlate well with [antiepileptic drugs] load in patients, which suggests that they are viable markers of cortical excitability in humans. This is further supported by their correlation with stimulation-evoked responses — the current gold standard for excitability measurements — in human subdural recordings. We uncover a characteristic modulation over 24 [hours] in line with the hypothesis of a progressively increasing excitability during wakefulness that is rebalanced during sleep,” Meisel and colleagues wrote.

These study findings, which indicate versatile monitoring of excitability levels, could lead to more individualized treatment strategies. – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.