A comparison of resting-state brain activity in humans and chimpanzees

doi:10.1073/pnas.0705132104

A comparison of resting-state brain activity in humans and chimpanzees

*Department of Anthropology, Centers for
^†Behavioral Neuroscience and
^‡‡Positron Emission Tomography,
Divisions of ^‡Psychobiology and
^‖Neuroscience, Yerkes National Primate Research Center, and
Departments of ^§Psychiatry and Behavioral Sciences,
**Pathology, and
^††Radiology, Emory University School of Medicine, Emory University, Atlanta, GA 30322

Edited by Marcus E. Raichle, Washington University School of Medicine, St. Louis, MO, and approved September 6, 2007 (received for review May 31, 2007)

Abstract

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.

Footnotes

^¶To whom correspondence should be addressed. E-mail: jrillin{at}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.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0705132104/DC1.
Abbreviations:

FDG,

[18F]-fluorodeoxyglucose;

PET,

positron emission tomography;

BA,

Brodmann's area;

PFC,

prefrontal cortex;

MPFC,

medial PFC.