Decoding neuronal ensembles in the human hippocampus.
BACKGROUND
The hippocampus underpins our ability to navigate, to form and recollect memories, and to imagine future experiences. How activity across millions of hippocampal neurons supports these functions is a fundamental question in neuroscience, wherein the size, sparseness, and organization of the hippocampal neural code are debated.


RESULTS
Here, by using multivariate pattern classification and high spatial resolution functional MRI, we decoded activity across the population of neurons in the human medial temporal lobe while participants navigated in a virtual reality environment. Remarkably, we could accurately predict the position of an individual within this environment solely from the pattern of activity in his hippocampus even when visual input and task were held constant. Moreover, we observed a dissociation between responses in the hippocampus and parahippocampal gyrus, suggesting that they play differing roles in navigation.


CONCLUSIONS
These results show that highly abstracted representations of space are expressed in the human hippocampus. Furthermore, our findings have implications for understanding the hippocampal population code and suggest that, contrary to current consensus, neuronal ensembles representing place memories must be large and have an anisotropic structure.
Hassabis
Demis
D
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK. d.hassabis@fil.ion.ucl.ac.uk
Chu
Carlton
C
Rees
Geraint
G
Weiskopf
Nikolaus
N
Molyneux
Peter D
PD
Maguire
Eleanor A
EA
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D006624:Hippocampus / Q000166:cytology / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D009043:Motor Activity / Q000502:physiology; D015999:Multivariate Analysis; D009415:Nerve Net / Q000033:anatomy & histology / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D013028:Space Perception / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology; D055815:Young Adult