Abstract

Patients with hippocampal amnesia play a central role in memory neuroscience but the neural underpinnings of amnesia are hotly debated. We hypothesized that focal hippocampal damage is associated with changes across the extended hippocampal system and that these, rather than hippocampal atrophy per se, would explain variability in memory between patients. We assessed this hypothesis in a uniquely large cohort of patients (n=38) after autoimmune limbic encephalitis, a syndrome associated with focal structural hippocampal pathology. These patients showed impaired recall, recognition and maintenance of new information, and remote autobiographical amnesia. Besides hippocampal atrophy, we observed correlatively reduced thalamic and entorhinal cortical volume, resting-state inter-hippocampal connectivity and activity in posteromedial cortex. Associations of hippocampal volume with recall, recognition, and remote memory were fully mediated by wider network abnormalities, and were only direct in forgetting. Network abnormalities may explain the variability across studies of amnesia and speak to debates in memory neuroscience.

Data availability

A source data file has been provided for the plots in Figure 2- figure supplement 1, and main figures 3-8. The participants of our study had not been asked to consent for their anonymized data to be publicly shared and be made freely available. Therefore, these data are available through a request to Dr Georgios Argyropoulos and would need to be approved by an ethics committee. Information relating to the 32 MRI datasets previously collected and made available via the Oxford Project To Investigate Memory and Aging can be found here https://www.ndcn.ox.ac.uk/research/centre-prevention-stroke-dementia/resources/optima-oxford-project-to-investigate-memory-and-ageing and requests to access made to Dr. Christopher Butler.

Article and author information

Author details

  1. Georgios P D Argyropoulos

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    For correspondence
    georgios.argyropoulos@ndcn.ox.ac.uk
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-8267-6861
  2. Clare Loane

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    Competing interests
    No competing interests declared.
  3. Adriana Roca-Fernandez

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    Competing interests
    No competing interests declared.
  4. Carmen Lage-Martinez

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    Competing interests
    No competing interests declared.
  5. Oana Gurau

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    Competing interests
    No competing interests declared.
  6. Sarosh R Irani

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    Competing interests
    Sarosh R Irani, is a coapplicant and receives royalties on patent application WO/2010/046716 (U.K. patent no., PCT/GB2009/051441) entitled 'Neurological Autoimmune Disorders'. The patent has been licensed to Euroimmun AG for the development of assays for LGI1 and other VGKC-complex antibodies..
  7. Christopher R Butler

    Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
    Competing interests
    No competing interests declared.

Funding

Medical Research Council (MR/K010395/1)

  • Christopher R Butler

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Human subjects: All participants provided written informed consent according to the Declaration of Helsinki. Ethical approval was received from South Central Oxford Research Ethics Committee (REC no: 08/H0606/133).

Copyright

© 2019, Argyropoulos et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 2,832
    views
  • 375
    downloads
  • 33
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Georgios P D Argyropoulos
  2. Clare Loane
  3. Adriana Roca-Fernandez
  4. Carmen Lage-Martinez
  5. Oana Gurau
  6. Sarosh R Irani
  7. Christopher R Butler
(2019)
Network-wide abnormalities explain memory variability in hippocampal amnesia
eLife 8:e46156.
https://doi.org/10.7554/eLife.46156

Share this article

https://doi.org/10.7554/eLife.46156

Further reading

    1. Neuroscience
    Christine Ahrends, Mark W Woolrich, Diego Vidaurre
    Tools and Resources

    Predicting an individual’s cognitive traits or clinical condition using brain signals is a central goal in modern neuroscience. This is commonly done using either structural aspects, such as structural connectivity or cortical thickness, or aggregated measures of brain activity that average over time. But these approaches are missing a central aspect of brain function: the unique ways in which an individual’s brain activity unfolds over time. One reason why these dynamic patterns are not usually considered is that they have to be described by complex, high-dimensional models; and it is unclear how best to use these models for prediction. We here propose an approach that describes dynamic functional connectivity and amplitude patterns using a Hidden Markov model (HMM) and combines it with the Fisher kernel, which can be used to predict individual traits. The Fisher kernel is constructed from the HMM in a mathematically principled manner, thereby preserving the structure of the underlying model. We show here, in fMRI data, that the HMM-Fisher kernel approach is accurate and reliable. We compare the Fisher kernel to other prediction methods, both time-varying and time-averaged functional connectivity-based models. Our approach leverages information about an individual’s time-varying amplitude and functional connectivity for prediction and has broad applications in cognitive neuroscience and personalised medicine.

    1. Neuroscience
    Jessica Royer, Valeria Kebets ... Boris C Bernhardt
    Research Article Updated

    Complex structural and functional changes occurring in typical and atypical development necessitate multidimensional approaches to better understand the risk of developing psychopathology. Here, we simultaneously examined structural and functional brain network patterns in relation to dimensions of psychopathology in the Adolescent Brain Cognitive Development (ABCD) dataset. Several components were identified, recapitulating the psychopathology hierarchy, with the general psychopathology (p) factor explaining most covariance with multimodal imaging features, while the internalizing, externalizing, and neurodevelopmental dimensions were each associated with distinct morphological and functional connectivity signatures. Connectivity signatures associated with the p factor and neurodevelopmental dimensions followed the sensory-to-transmodal axis of cortical organization, which is related to the emergence of complex cognition and risk for psychopathology. Results were consistent in two separate data subsamples and robust to variations in analytical parameters. Although model parameters yielded statistically significant brain–behavior associations in unseen data, generalizability of the model was rather limited for all three latent components (r change from within- to out-of-sample statistics: LC1within = 0.36, LC1out = 0.03; LC2within = 0.34, LC2out = 0.05; LC3within = 0.35, LC3out = 0.07). Our findings help in better understanding biological mechanisms underpinning dimensions of psychopathology, and could provide brain-based vulnerability markers.