Human hippocampal CA3 damage disrupts both recent and remote episodic memories
Thomas D Miller,
Trevor T-J Chong,
Anne M Aimola Davies,
Michael R Johnson,
Sarosh R Irani,
Masud Husain,
Tammy WC Ng,
Saiju Jacob,
Paul Maddison,
Christopher Kennard,
Penny A Gowland,
Clive R Rosenthal
Affiliations
Thomas D Miller
Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology, Royal Free Hospital, London, United Kingdom
Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Clayton, Australia
Anne M Aimola Davies
Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom; Research School of Psychology, Australian National University, Canberra, Australia
Michael R Johnson
Division of Brain Sciences, Imperial College London, London, United Kingdom
Sarosh R Irani
Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
Masud Husain
Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
Tammy WC Ng
Department of Anaesthestics, Royal Free Hospital, London, United Kingdom
Saiju Jacob
Neurology Department, Queen Elizabeth Neuroscience Centre, University Hospitals of Birmingham, Birmingham, United Kingdom
Paul Maddison
Neurology Department, Queen’s Medical Centre, Nottingham, United Kingdom
Christopher Kennard
Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
Penny A Gowland
Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom
Neocortical-hippocampal interactions support new episodic (event) memories, but there is conflicting evidence about the dependence of remote episodic memories on the hippocampus. In line with systems consolidation and computational theories of episodic memory, evidence from model organisms suggests that the cornu ammonis 3 (CA3) hippocampal subfield supports recent, but not remote, episodic retrieval. In this study, we demonstrated that recent and remote memories were susceptible to a loss of episodic detail in human participants with focal bilateral damage to CA3. Graph theoretic analyses of 7.0-Tesla resting-state fMRI data revealed that CA3 damage disrupted functional integration across the medial temporal lobe (MTL) subsystem of the default network. The loss of functional integration in MTL subsystem regions was predictive of autobiographical episodic retrieval performance. We conclude that human CA3 is necessary for the retrieval of episodic memories long after their initial acquisition and functional integration of the default network is important for autobiographical episodic memory performance.
