Thursday, April 08, 2010
fMRI measurents distinguish specific memories
It was bound to happen at some point - given the rapid refinement of fMRI measurement and analysis over the past few years. Eleanor Maguire and her colleagues at University College London report in Current Biology that different episodic memories can be distinguished as they are recalled. In their experiments fMRI signals from the hippocampus were measured as volunteers observed and were asked to memorize different 7-second movie clips. A computer algorithm was used to match the pattern of activity to each memory. When subjects were subsequently instructed to recall one of the movie clips, the algorithm performed much better than chance at determining which movie was being recalled. Their results show that highly abstracted representations of space are expressed across tens of thousands of coordinated neurons in our hippocampus in a structured manner. They suggest that, contrary to current consensus, neuronal ensembles representing place memories must be large and have an anisotropic structure.