September 2, 2009
Rats found to mentally re-enact events
U.S. scientists say they have discovered rats engage in a mental re-enactment of their recent experiences when choosing what actions to take.
Massachusetts Institute of Technology researchers said they recorded the activity of single neurons called
place cells in a brain structure -- the hippocampus -- that has been shown to be crucial for learning and memory. They found place cells are activated in a unique pattern and sequence for each specific location in a maze.
When examining the brain recordings, the scientists determined the same pattern and sequence of activation took place during pauses in activity, and when rats confronted a choice of routes in the maze. The researchers found while a rat is awake but standing still in the maze, its neurons fire in the same pattern of activity that occurred while it was running.
This may be the rat equivalent of 'thinking,' said Professor Matthew Wilson, who led the study.
This thinking process looks very much like the reactivation of memory that we see during non-REM dream states, consisting of bursts of time-compressed memory sequences lasting a fraction of a second. So thinking and dreaming may share the same memory reactivation mechanisms.
The researchers, who included Fabian Kloosterman and Thomas Davidson, say their findings might also reflect how memory systems fail in people with Alzheimer's disease and schizophrenia.
The study appears in the journal Neuron.