Rapid and independent memory formation in the parietal cortex.
Previous evidence indicates that the brain stores memory in two complementary systems, allowing both rapid plasticity and stable representations at different sites. For memory to be established in a long-lasting neocortical store, many learning repetitions are considered necessary after initial encoding into hippocampal circuits. To elucidate the dynamics of hippocampal and neocortical contributions to the early phases of memory formation, we closely followed changes in human functional brain activity while volunteers navigated through two different, initially unknown virtual environments. In one condition, they were able to encode new information continuously about the spatial layout of the maze. In the control condition, no information could be learned because the layout changed constantly. Our results show that the posterior parietal cortex (PPC) encodes memories for spatial locations rapidly, beginning already with the first visit to a location and steadily increasing activity with each additional encounter. Hippocampal activity and connectivity between the PPC and hippocampus, on the other hand, are strongest during initial encoding, and both decline with additional encounters. Importantly, stronger PPC activity related to higher memory-based performance. Compared with the nonlearnable control condition, PPC activity in the learned environment remained elevated after a 24-h interval, indicating a stable change. Our findings reflect the rapid creation of a memory representation in the PPC, which belongs to a recently proposed parietal memory network. The emerging parietal representation is specific for individual episodes of experience, predicts behavior, and remains stable over offline periods, and must therefore hold a mnemonic function.
Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-Universität Tübingen, 72076 Tuebingen, Germany.
Svenja
S
Brodt
Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-Universität Tübingen, 72076 Tuebingen, Germany.
Dorothee
D
Pöhlchen
German Center for Vertigo and Balance Disorders, University Hospital Munich, 81377 Munich, Germany.|Bernstein Center for Computational Neuroscience, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.
Virginia L
VL
Flanagin
German Center for Vertigo and Balance Disorders, University Hospital Munich, 81377 Munich, Germany.|Bernstein Center for Computational Neuroscience, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.|Center for Sensorimotor Research, Department of Neurology, University Hospital Munich, 81377 Munich, Germany.
Stefan
S
Glasauer
Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-Universität Tübingen, 72076 Tuebingen, Germany; steffen.gais@uni-tuebingen.de.|Bernstein Center for Computational Neuroscience, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.
Steffen
S
Gais
Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-Universität Tübingen, 72076 Tuebingen, Germany.|Bernstein Center for Computational Neuroscience, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.
Monika
M
Schönauer
D000328:Adult; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D010296:Parietal Lobe / Q000000981:diagnostic imaging / Q000502:physiology*; D065853:Spatial Learning; D000076142:Virtual Reality; D055815:Young Adult
long-term memory; memory systems consolidation; posterior parietal cortex; precuneus; virtual reality