FORMATION of a memory is widely believed to leave a ‘trace’ in the brain – a fleeting pattern of electrical activity which strengthens the connections within a widely distributed network of neurons, and which re-emerges when the memory is recalled. The concept of the memory trace was first proposed nearly a century ago, but the nature of the trace, its precise location in the brain and the underlying neural mechanisms all remain elusive. Researchers from University College London now report that functional magnetic resonance (fMRI) can be used to decode individual memory traces and to predict which of three recently encoded memories is being recalled.
The new study, led by Eleanor Maguire of the Wellcome Trust Centre for Neuroimaging, builds on earlier work which demonstrates that fMRI can be used to predict simple mental states from brain activity. Last year, Maguire and her colleagues showed that it is possible to predict an individual’s position in a virtual reality environment from patterns of activity in the hippocampus, and researchers from Vanderbilt University showed that activity in the visual cortex can be decoded to predict which image is being retained in working memory. Even more remarkably, Japanese researchers have reconstructed visual images from brain activity, including novel ones that their participants had never seen before.