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Published July 2015 | Accepted Version + Supplemental Material
Journal Article Open

Representation of retrieval confidence by single neurons in the human medial temporal lobe


Memory-based decisions are often accompanied by an assessment of choice certainty, but the mechanisms of such confidence judgments remain unknown. We studied the response of 1,065 individual neurons in the human hippocampus and amygdala while neurosurgical patients made memory retrieval decisions together with a confidence judgment. Combining behavioral, neuronal and computational analysis, we identified a population of memory-selective (MS) neurons whose activity signaled stimulus familiarity and confidence, as assessed by subjective report. In contrast, the activity of visually selective (VS) neurons was not sensitive to memory strength. The groups further differed in response latency, tuning and extracellular waveforms. The information provided by MS neurons was sufficient for a race model to decide stimulus familiarity and retrieval confidence. Together, our results indicate a trial-by-trial relationship between a specific group of neurons and declared memory strength in humans. We suggest that VS and MS neurons are a substrate for declarative memories.

Additional Information

© 2015 Macmillan Publishers Limited. Received 1 April; accepted 13 May; published online 8 June 2015. We thank J. Kaminski, R. Adolphs, C. Anastassiou, U. Maoz, J. Wertheimer and W. Einhaeuser for discussion, Z. Fu for spike sorting, C. Heller for performing some of the surgeries, the staff of the Epilepsy Monitoring Units at Huntington Memorial Hospital and Cedars-Sinai for invaluable assistance, particularly J. Schmidt. We thank K. Birch and H. Babu for assistance with patient care and surgery, and L. Philpott and M.-T. Le for neuropsychological testing. This work was supported by the Cedars-Sinai Medical Center Department of Neurosurgery (to U.R.), National Institute of Mental Health Conte Center at Caltech (P50 MH094258), and the Gustavus and Louise Pfeiffer Research Foundation (to U.R.). Author Contributions: U.R. and A.N.M. designed the experiments. U.R. and O.T. performed experiments. U.R., M.K. and S.Y. performed analysis. A.N.M. and I.B.R. performed surgery. J.M.C. provided patient care. U.R. and A.N.M. wrote the paper. All of the authors discussed the results at all stages of the project.

Attached Files

Accepted Version - nihms691602.pdf

Supplemental Material - nn.4041-S1.pdf

Supplemental Material - nn.4041-S2.pdf


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