Our sleep cycle has alternate phases of REM (rapid eye movement) & NREM (non-rapid eye movement) sleep. REM sleep (25% of total sleep) is characterized by side-to-side eye movement along with increased brain activity and the best part of it all, vivid dreams.
A recent study conducted on a mouse suggests that eye movements during REM sleep are the change in direction of the animal’s gaze in the dream.
- The researchers assessed a special group of cells that is responsible for head movement in the horizontal plane called head direction cells. These cells emulate the working of a compass, meaning that the direction the mouse perceives is where they are most likely to go.
- A set of lightweight head-mounted cameras were used to track the awake mouse as it explored the environment. The recordings helped with the conclusion that a specific pattern of activity in head direction cells has brought about this head movement.
- Later it was predicted that the eye movement and the activity of head direction cells are heavily related. This indicates that even in the state of rest the coordinated eye movements reflect the shift in the gaze of the mice in their dream world.
A conflicting view about eye movements in REM sleep simply suggests that it’s the motor region of the brain that sends signals to the muscle during REM sleep, causing them to twitch which in turn sends feedback to the sensory region, which again signals the motor region, thus completing a feedback loop.