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Author Notes:

To whom correspondence should be addressed: James K. Rilling (Email: jrillin@emory.edu)

Author contributions: J.K.R., L.A.P., and T.M.P. designed research; J.K.R., S.K.B., L.A.P., J.D.B., and J.R.V. performed research; T.L.F. contributed new reagents/analytic tools; J.K.R., S.K.B., and G.P. analyzed data; and J.K.R. and T.M.P. wrote the paper.

We thank Dr. William Hopkins, Mr. Matthew Glasser, Ms. Sheila Sterk, Mr. Matt Heintz, and Dr. Mary Dent for assistance with various aspects of this study.

The authors declare no conflict of interest.


Research Funding:

Grant support was provided by the Center for Behavioral Neuroscience Science and Technology Center Program of the National Science Foundation under agreement no. IBN-9876754; National Institutes of Health (NIH)/National Center for Research Resources Grant RR-00165 to the Yerkes National Primate Research Center and NIH Grant R01-MH068791 (to L.A.P.).


  • comparative cognition
  • neuroimaging
  • default mode

Journal Title:

Proceedings of the National Academy of Sciences


Volume 104, Number 43


, Pages 17146-17151

Type of Work:

Article | Post-print: After Peer Review


In humans, the wakeful resting condition is characterized by a default mode of brain function involving high levels of activity within a functionally connected network of brain regions. This network has recently been implicated in mental self-projection into the past, the future, or another individual's perspective. Here we use [18F]-fluorodeoxyglucose positron emission tomography imaging to assess resting-state brain activity in our closest living relative, the chimpanzee, as a potential window onto their mental world and compare these results with those of a human sample. We find that, like humans, chimpanzees show high levels of activity within default mode areas, including medial prefrontal and medial parietal cortex. Chimpanzees differ from our human sample in showing higher levels of activity in ventromedial prefrontal cortex and lower levels of activity in left-sided cortical areas involved in language and conceptual processing in humans. Our results raise the possibility that the resting state of chimpanzees involves emotionally laden episodic memory retrieval and some level of mental self-projection, albeit in the absence of language and conceptual processing.

Copyright information:

© 2007 by The National Academy of Sciences of the USA

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