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

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 [ 18 F]-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.comparative cognition ͉ neuroimaging ͉ default mode

Metabolic and structural connectivity within the default mode network relates to working memory performance in young healthy adults

“…The pattern of the DMN (MPFC, PCC, inferior parietal cortex) we observed is well in agreement with previous resting state metabolic PET (Rilling et al, 2007) as well as fMRI (for a review see van den Heuvel and Hulshoff Pol, 2010) studies. Consistent with the definition of the DMN, the above regions are typically deactivated during performance of a WM task in fMRI experiments (Anticevic et al, 2010;Hampson et al, 2006;Tomasi et al, 2006).…”

“…As opposed to fMRI, FDG-PET captures neuronal activity that is in steady state in hourly terms and is independent of vascular coupling. This neuroimaging tool may hence be well suitable for exploring the baseline integrity of neuronal networks (Rocher et al, 2003) such as the DMN (Lee et al, 2008;Rilling et al, 2007). Although proposed more than 25 years ago (Clark et al, 1984;Horwitz et al, 1984;Metter et al, 1984), the method of interregional correlations has been validated for whole brain voxel-wise analyses only recently (Lee et al, 2008).…”

Chimpanzee (Pan troglodytes) and orangutan (Pongo abelii) forethought: self-control and pre-experience in the face of future tool use

“…Furthermore, they imply that apes use cognition described as self-conscious when exhibited by humans. The results Wt well with the neurological data indicating an experienced inner mental world in chimpanzees (Rilling et al 2007). The Wndings are interesting when considering the study of extant great apes as well as when discussing the evolution of human cognition.…”

“…The question about the related skill of episodic prospection in non-humans will be dealt with further. However, it should be mentioned that the speciWc brain state at wakeful rest, that is strongly linked to mental self-projection in humans (e.g., ChristoV et al 2004;Andreasen et al 1995;Ingvar 1979), has currently been reported to have a counterpart in chimpanzees (Rilling et al 2007).…”

Empirical approaches to the study of language evolution

“…This allows in vivo analysis of the anatomical connectivity of different regions, and how they vary between species (e.g., Rilling et al, 2008). Such analyses are complemented by functional connectivity analysis (which uses cross-correlation in time across multiple brain areas) to evaluate which regions are coactivated in particular tasks (Sporns et al, 2004;Xiang et al, 2010;Hamilton et al, 2013), an approach also potentially applicable to interspecies comparisons (Rilling et al, 2007). Such approaches have led to important advances in our understanding of the neural computations that underlie language, including the still ongoing debate about whether any are specific to language or not (cf.…”