The new detectors can reduce the length of seizures in rats by up to 60 per cent.
Epilepsy, a condition of the brain which results in unprovoked and recurrent seizures, affects approximately one in every 120 people in Australia. Although these seizures can usually be controlled by medication, epilepsy can still have profound social, physical and psychological consequences. While electrical stimulation devices have been developed, such as those that deliver deep brain stimulations (DBS), these operate continuously, regardless of whether the patient needs it or not, resulting in a number of undesirable side effects, such as headaches.
Researchers at the New York School of Medicine, lead by GyÃ¶rgy BuzsÃ¡ki, have developed a less invasive approach that involves transcranial electrical stimulation (TES) of neurons using electrodes implanted in the skull. These can detect an epileptic seizure and deliver therapeutic electrical impulses that can reduce the length of seizures by up to 60 per cent in rats. According to BuzsÃ¡ki, this is a method superior to DBS.
“We wanted to demonstrate that taking a particular pattern from the brain, such as epileptic activity, and feeding back electrical signals to the brain can modify brain activity online,” BuzsÃ¡ki says. “Interfering with the activity of the cerebral cortex continuously would make it useless. However, when the interference pattern is given when it already malfunctions, the method is able to ‘reset’ normal brain activity, so to speak.”
This procedure works by placing metal plates the size of a large coin on the scalp (or in the researcher’s case, on the external surface of the skull for chronic use) and connecting it to a current source. Neurons in the brain communicate with electrical pulses, and their membrane can be excited by electric fields, which can be created by the applying current through the plates. The stimulation is typically not perceived by the subject, except in some cases due to feeling the skin stimulation, or seeing ‘sparks’.
“The goal of deep brain stimulation is to apply stimulation locally. When the goal is to increase or synchronise activity over large areas of the brain, DBS is not effective,” says BuzsÃ¡ki. “In many conditions, diffuse stimulation of parts of the neocortex is more desirable.”
The effectiveness of TES, or ‘closed-loop’ stimulation, has two requirements: first, there needs to be a clear detection of a pathological pattern that is to be abolished, or a normal pattern (e.g. sleep spindles) that is to be enhanced. Secondly, appropriate patterns of stimulation need to be fed back to the brain at the right time and the right place. “The second requirement is pretty tough in many diseases, since we have no clue about the what and where issues,” BuzsÃ¡ki claims. “For example, clear advancement would be to apply our method to complex partial seizures, since a large fraction of these patients are resistant to drug medication. However, what will be the right structure and the effective waveform requires further serious research in animals.”
This research has the potential to not only break epileptic seizures, but also modify brain activity in selected psychiatric diseases and affect sleep and change sleep patterns. “Now that the major pharmaceutical companies are discontinuing research on the brain, other alternative methods will come of age,” states BuzsÃ¡ki. “Closed-loop electrical stimulation, which can be applied on the ‘when-needed’ basis is a promising new direction.”