Brain takes seconds to switch modes during tasks

The brain rapidly switches between operational modes in response to tasks and what is replayed can predict how well a task will be completed, according to a new UCL study in rats. "We know that the brain replays remembered experiences during rest to extract important information, this consolidation process preserves memories for recall in the future. But replay is also important for planning" explained lead researcher, Dr Freyja Ólafsdóttir (UCL Cell & Developmental Biology). "We wanted to see how replay changed while animals carried out simple spatial tasks and found that it only takes 10-15 secs for the brain to switch from a mode in which replay occurs to support planning - when the rat is engaged in a task - to a mode supporting memory consolidation - when it is resting." The study, published today in Neuron and funded by Wellcome and the Royal Society, provides the first evidence that switching between modes occurs dynamically according to the demands of the task and that replay is important for spatial behaviour. Eight rats ran on a Z-shaped track at their own pace. At each corner, when they took the correct path, the animals were rewarded with food. While the rats paused at the corner, the team studied the responses of place cells in the hippocampus, where planning happens and memories are formed, and grid cells in the entorhinal cortex, which is believed to be important for consolidation.