Decoding Individual Episodic Memory Traces in the Human Hippocampus

Martin J Chadwick,Demis Hassabis,Nikolaus Weiskopf,Eleanor A Maguire

doi:10.1016/j.cub.2010.01.053

Martin J Chadwick, Demis Hassabis + Show 2 more

Open Access

https://doi.org/10.1016/j.cub.2010.01.053

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Journal: Current Biology	Publication Date: Mar 1, 2010
Citations: 222	License type: cc-by

Affiliation: Wellcome Centre for Human Neuroimaging

Abstract

SummaryIn recent years, multivariate pattern analyses have been performed on functional magnetic resonance imaging (fMRI) data, permitting prediction of mental states from local patterns of blood oxygen-level-dependent (BOLD) signal across voxels [1, 2]. We previously demonstrated that it is possible to predict the position of individuals in a virtual-reality environment from the pattern of activity across voxels in the hippocampus [3]. Although this shows that spatial memories can be decoded, substantially more challenging, and arguably only possible to investigate in humans [4], is whether it is feasible to predict which complex everyday experience, or episodic memory, a person is recalling. Here we document for the first time that traces of individual rich episodic memories are detectable and distinguishable solely from the pattern of fMRI BOLD signals across voxels in the human hippocampus. In so doing, we uncovered a possible functional topography in the hippocampus, with preferential episodic processing by some hippocampal regions over others. Moreover, our results imply that the neuronal traces of episodic memories are stable (and thus predictable) even over many re-activations. Finally, our data provide further evidence for functional differentiation within the medial temporal lobe, in that we show the hippocampus contains significantly more episodic information than adjacent structures.

Highlights

The components of a complex multimodal memory, such as a rich episodic memory, are likely to be widely distributed throughout the cortex [9]
Something must bind the disparate elements of a recent episodic memory together to allow the relevant neural representations to coactivate, facilitating recollection [10]
Given that the entorhinal cortex (EC) and posterior parahippocampal gyrus (PHG) are both major input pathways to the hippocampus [17], we investigated whether these regions might contain episodic information

Summary

Introduction

MVPA was used to decode spatial information and predict the location of participants in a virtual-reality environment from the pattern of fMRI signals across voxels in the human hippocampus [3]. Using high-spatial-resolution fMRI, we investigated whether it would be possible to predict which specific recent episodic memory a participant was recalling solely on the basis of the blood oxygen-leveldependent (BOLD) activity patterns across voxels in the hippocampus, potentially distinguishing specific memory traces.

Results

Conclusion