Treatment for Epilepsy Expands Understanding of Sleep

"The more scientists research how we sleep, the more they discover how important sleeping is to our overall health and wellbeing. But those aren't the only sleep-related discoveries scientists are making. The latest high-profile finding is less about the benefits of sleep and more connected to how the brain behaves during sleep, something that could have wider implications for our understanding of the human body."

"In the paper, published in the journal PLOS Biology, its authors discuss a medical procedure called hemispherotomy. This is used in situations when a patient has refractory epilepsy, a form of epilepsy that does not respond to medication. The paper's authors describe this procedure as involving "disconnecting a significant portion of the cortex, potentially encompassing an entire hemisphere, from its cortical and subcortical connections.""

"When the researchers studied the part of the cortex they had disconnected, they found it was in a state resembling slumber, despite the subjects being awake. "[T]he isolated cortex was consistent with deep NREM sleep," they wrote. As Rachel Fieldhouse explained in an article for Nature, this raises larger questions about the nature of consciousness and memory. As Marcello Massimini, one of the paper's authors, explained to Nature, the implications of these findings go beyond how doctors might respond to epilepsy."

Hemispherotomy disconnects a large portion of cortex, potentially an entire hemisphere, from cortical and subcortical connections to treat refractory epilepsy. Examined isolated cortical tissue displayed neural activity consistent with deep NREM sleep while subjects remained clinically awake. The sleep-like state occurred despite external wakefulness, indicating that local cortical states can diverge from global behavioral consciousness. Similar neural patterns have been observed after stroke and traumatic brain injury, suggesting a broader phenomenon across different brain insults. Observations imply new avenues for understanding consciousness, memory, and clinical approaches to brain injury and epilepsy, and suggest targeted future research on local cortical state dynamics.

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