The idea of electrically stimulating a brain region called the central thalamus has gained traction among researchers and clinicians because it can help arouse subjects from unconscious states induced by traumatic brain injury or anesthesia, and can boost cognition and performance in awake animals. But the method, called CT-DBS, can have a side effect: seizures. A new study by researchers at MIT and Massachusetts General Hospital (MGH), who tested the method in awake mice, quantifies the probability of seizures at different stimulation currents and cautions that they sometimes occur even at low levels.
The work appears in Brain Stimulation . "Understanding production and prevalence of this type of seizure activity is important because brain stimulation-based therapies are becoming more widely used," said co-senior author Emery N. Brown.
In the brain, the seizures associated with CT-DBS occur as "electrographic seizures," which are bursts of voltage among neurons across a broad spectrum of frequencies. Behaviorally, they manifest as " absence seizures " in which the subject appears to take on a blank stare and freezes for about 10–20 seconds. In their study, the researchers were hoping to determine a CT-DBS stimulation current— in a clinically relevant range of under 200 microamps—below which seizures could be reliably avoided.
In search of that ideal current, they developed a protocol of starting brief bouts of CT-DBS at 1 microamp and then incrementally ramping the cur.