Researchers have discovered changes in the brain associated with LSD which they say could help gain insights into how the brain generates behaviour.
The team at Baylor College of Medicine have discovered changes in the brain triggered by LSD that may explain the altered behaviour associated with the compound. Published in the journal Cell Reports the findings demonstrated that rats that had been given LSD altered their running behaviour in a track they were familiar with compared to rats that had not been given the compound, and also increased their resting time.
During this time the rats entered what the scientists describe as a state of being half-awake and half-asleep.
Corresponding author and professor of neuroscience at Baylor, Dr Daoyun Ji, commented: “Our lab is interested in improving the understanding of how the brain generates behaviour.
“LSD triggers abnormal perceptions of the real world and altered behaviours. By studying how the drug works, we hope to gain insights into the neural mechanisms that mediate behaviour.”
During this half-awake and half-asleep state, the researchers observed a reduction of the normal communication between the hippocampus and the visual cortex in the brain. This reduction in communication may explain the changed behaviours according to the team.
Ji and his colleagues looked at the animals’ behaviour and their simultaneous brain activity with and without LSD, as the rats were running in a familiar C-shaped track, recording the number of laps the animals ran on the track and as well as how fast they ran. In order to measure brain activity, the researchers recorded the brain cells’ electrical spiking patterns in real-time in the hippocampus and the visual cortex.
The team found that the animals receiving the drug ran fewer laps and moved slower than those without LSD, and that the overall spiking activity of the hippocampus and visual cortex neurons was greatly reduced in the animals that received LSD. The rats receiving the LSD also had more periods of inactivity in the track.
“That means that when the animal was moving around in the track, the neurons generated fewer pulses, which probably affected the clarity of their guiding brain ‘map,’” Ji said.
Animal brains naturally develop a ‘map’ when moving around an environment in order to know where it is and how to go from point A to point B, allowing the animal to remember the place and guides future navigation in the same space. The hippocampus and the visual cortex work together to create this map.
The team say that the LSD changed the spiking patterns that sustain this map, including what gives the animal direction, and the communication between the visual cortex and the hippocampus.
The authors state: “When rats are immobile on the track, LSD enhances cortical firing synchrony in a state similar to the wakefulness-to-sleep transition, during which the hippocampal-cortical interaction remains dampened while hippocampal awake reactivation is maintained.
“Our results suggest that LSD suppresses hippocampal-cortical interactions during active behaviour and during immobility, leading to internal hippocampal representations that are degraded and isolated from external sensory input. These effects may contribute to LSD-produced abnormal perceptions.”
“We propose that LSD makes the map fuzzy,” Ji said. “These periods of inactivity triggered by LSD are like the normal transition from being awake to going to sleep. It suggests that maybe the drug induces a state similar to a half-conscious state in which a lot of dreaming-like activity is happening. More research is needed to enlighten this finding.”
