Ready ... Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time
Abstract
What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations, we found little fMRI activity during the waiting period; however, a large signal appears after the "go" signal, the amplitude of which reflects learned expectations about the distribution of possible waiting times. Specifically, the amplitude of the fMRI signal appears to encode a cumulative conditional probability, also known as the cumulative hazard function. The fMRI signal loses its dependence on waiting time in a "countdown" condition in which the arrival time of the go cue is known in advance, suggesting that the signal encodes temporal probabilities rather than simply elapsed time. The dependence of the signal on temporal expectation is present in "no-go" conditions, demonstrating that the effect is not a consequence of motor output. Finally, the encoding is not dependent on modality, operating in the same manner with auditory or visual signals. This finding extends our understanding of the relationship between temporal expectancy and measurable neural signals.
Additional Information
© 2009 Cui et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: XC CS PRM DME. Performed the experiments: XC CS. Analyzed the data: XC CS. Contributed reagents/materials/analysis tools: XC CS PRM DME. Wrote the paper: XC CS PRM DME. This work was supported by National Institute of Neurological Disorders and Stroke (NINDS) RO1 grant NS053960 (DME), as well as National Institute on Drug Abuse R01 grant DA11723, the Kane Family Foundation and NINDS grant NS045790 (PRM), and the Sloan-Swartz Foundation (CS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Supporting Information Figure S1 Reaction times correlate with readiness periods on the basis of the underlying probability distributions (insets). Circle area is proportional to the sample size within block. These data match the previously documented relationship between readiness period and reaction time (the variable foreperiod effect1–3), verifying that our participants learned the structure of the temporal probability distributions. Symbol diameter is proportional to the number of samples within each experiment. Error bars are standard error of the mean (SEM). Found at: doi:10.1371/journal.pbio.1000167.s001 (0.17 MB TIF) Figure S2 A revision of the plot from Curtis and Connolly [24] that aligns the onset time of the go-cue reveals a result like that seen in our Figure 1. Found at: doi:10.1371/journal.pbio.1000167.s002 (0.91 MB TIF) Text S1 Supplementary material. Found at: doi:10.1371/journal.pbio.1000167.s003 (0.06 MB DOC)Errata
Formal Correction: This article has been formally corrected to address the following errors. 1. An affiliation was omitted for the third author. P. Read Montague is also affiliated with: Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, Texas, United States of America.Attached Files
Published - Cui2009p5857Plos_Biol.pdf
Supplemental Material - journal.pbio.1000167.s001.tif
Supplemental Material - journal.pbio.1000167.s002.tif
Supplemental Material - journal.pbio.1000167.s003.doc
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Additional details
- PMCID
- PMC2711330
- Eprint ID
- 15792
- Resolver ID
- CaltechAUTHORS:20090911-153558851
- R01 NS053960
- National Institute of Neurological Disorders and Stroke
- R01 DA11723
- National Institute on Drug Abuse
- Kane Family Foundation
- NS045790
- National Institute of Neurological Disorders and Stroke
- Sloan-Swartz Foundation
- Created
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2009-10-02Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field