England: Slow waves, which are normally only present in the brain during sleep, are also present when awake in patients with epilepsy and may protect against the condition's heightened brain excitability, according to a new study led by UCL researchers.
The research, published in Nature Communications and involving the National Institute for Health and Care Research (NIHR) UCLH Biomedical Research Centre, examined electroencephalogram (EEG) scans from electrodes in the brains of 25 patients with focal epilepsy (a type of epilepsy characterised by seizures arising from a specific part of the brain), while they carried out an associative memory task.
The electrodes had been placed in the patients' brains to localise abnormal activity and inform surgical treatment. During the task, participants were presented with 27 pairs of images that remained on a screen for six seconds. The images were in nine groups of three - each group featuring a picture of a person, a place and an object. In each case, participants had to remember which images had been grouped together.
EEG data were recorded continuously throughout the task. After reviewing the EEG data, the team found that the brains of people with epilepsy were producing slow waves - lasting less than one second - while they were awake and taking part in the task.
The occurrence of these "wake" slow waves increased in line with increases in brain excitability and decreased the impact of epileptic spikes on brain activity.
In particular, there was a decrease in the "firing" of nerve cells, which the researchers say could protect against epileptic activity.
"This study unveils, for the first time, a potential protective mechanism, 'wake' slow waves, employed by the brain to counteract epileptic activity. This mechanism takes advantage of protective brain activity that normally occurs during sleep, but, in people with epilepsy, can occur during wakefulness." As part of the research, the team also wanted to test if the occurrence of "wake" slow waves had any negative effects on cognitive function.
During the memory task, researchers found that the "wake" slow waves reduced nerve cell activity and so affected cognitive performance - increasing the length of time required by patients to complete the task. (with Agency inputs)
