Ketamine Switches Brain 'Off and On,' Potentially Explaining K-holes

Ketamine appears to switch the brain "off and on," experiments on sheep have revealed. Researchers were giving the animals doses of the drug as part of a study into Huntington's disease when they made the surprise discovery.

Sheep were given different doses of ketamine and researchers recorded what was happening to their brain activity using electroencephalography (EEG). At lower doses, brain activity was found to switch between high and low frequency: "As the sheep came round from the ketamine, their brain activity was really unusual," research leader Jenny Morton, from the University of Cambridge, U.K., said in a statement.

She said the timing of these patterns appears to correspond to the period when humans using ketamine report feeling disconnected from their bodies. The changes in activity may prevent the brain from processing information normally.

At higher doses, the effect was stronger, with the brain appearing to switch off completely. "This wasn't just reduced brain activity," Morton said. "After the high dose of ketamine the brains of these sheep completely stopped. We've never seen that before. A few minutes later their brains were functioning normally again—it was as though they had just been switched off and on."

This effect was seen in five of the six sheep the higher dose of the drug was tested on. The pause, the team say, may relate to what is known as a "K-hole." This is where people who abuse ketamine enter a state where they are completely disassociated with their bodies. It is described as an intense out-of-body sensation similar to the way people describe near-death experiences.

Researchers warn taking ketamine at these high doses is extremely dangerous. According to a review of the drug by the World Health Organization, it appears to stimulate the cardiovascular system causing changes in heart rate and blood pressure. It also acts as a mild respiratory depressant. In rare cases, overdose can be fatal. According to the American Addiction Centers, if someone is paralyzed by the drug they can choke to death if they start vomiting. The effects of the ketamine mean users can end up in dangerous situations and suffer injuries.

Findings from the study are published in Scientific Reports.

Morton told Newsweek that once the effect of the drug wore off, the sheep behaved completely normally. She said the EEG findings are translatable to humans. However, one of the main limitations of the paper is that there is no way of telling what the sheep were experiencing while under the influence of the ketamine. Hallucinations among human users normally take place after the anaesthetic phase of the drug, she said.

"Ketamine is a valuable clinical drug—but limited by the hallucinations that occur in some adults when the anaesthetic effects wear off," Morton said. "If we could understand the mechanisms causing the hallucinations, it may be possible to block them so ketamine can be used to its full clinical potential."

brain hallucinate
Stock photo of a brain hallucination. Researchers tested different doses of ketamine on sheep to look at brain activity after the drug was taken. iStock