We are interested in why our brain is organized the way it is. Specifically, we are interested in how differences in brain organization, for instance between different primate species' brains or between different individuals, are related to differences in behavioral repertoires. Roughly, our work can be divided into three themes.

Mapping brain organization Mapping the brains of different species in terms of the anatomical and functional organization. We mostly focus on connectivity, but in principle we are any type of organization and investigating the relationship between levels.

Between-species comparisons We develop and apply methods for large-scale but detailed comparative neuroscience.

What does it do? Understanding the differences between brains is only useful if we can use that information to understand how it influences the behavioral abilities of any given brain. This is part of our work focuses mostly on the unique abilities of the human brain.


Mapping brain organization

This part of our research is aimed at mapping areas of the brain in humans and non-human primates and to investigate the connections between these areas. We use a variety of MRI-based techniques to study different aspects of brain organization. To study connectivity, we have extensively used the technique of resting state fMRI to compare mouse, macaque, and human brains. To extend our range of species we have pioneered the application of post-mortem diffusion MRI, which allows us to map the major white matter bundles in primates and non-primate mammals.

Some key publications:

Bryant KL, Li L, Eichert N, & Mars RB (2020) A comprehensive atlas of white matter tracts in the chimpanzee. PLoS Biology 18:e3000810
Blazquez Freches G, Haak K, Bryant KL, Schurz M, Beckmann CF, & Mars RB (2020) Principles of temporal association cortex organisation as revealed by connectivity gradients. Brain Structure and Function 225:1245-1260
Mars RB, Foxley S, Jbabdi S, Sallet J, Noonan MP, Andersson JL, Verhagen L, Croxson PL, Dunbar RIM, Khrapitchev AA, Sibson N, Miller KL, & Rushworth MFS (2016) The extreme capsule fiber complex in humans and macaques: A comparative diffusion MRI tractography study. Brain Structure and Function 221:4059-4071
Neubert FX, Mars RB, Sallet J, & Rushworth MFS (2015) Connectivity reveals relationship of brain areas for reward-guided learning and decision making in human and monkey frontal cortex. Proceedings of the National Academy of Sciences USA 112:E2695-E2704
Neubert FX, Mars RB, Thomas AG, Sallet J, & Rushworth MFS (2014) Comparison of human ventral frontal cortex areas for cognitive control and language with areas in monkey frontal cortex. Neuron 81:700-713
Sallet J, Mars RB, Noonan MP, Neubert FX, Jbabdi S, O'Reilly JX, Filippini N, Thomas A, & Rushworth MFS (2013) The organization of dorsal prefrontal cortex in humans and macaques. Journal of Neuroscience 33:12255-12274
Mars RB, Sallet J, Schüffelgen U, Jbabdi S, Toni I, & Rushworth MFS (2012) Connectivity-based subdivisions of the human right 'temporoparietal junction area' (TPJ): Evidence for different areas participating in different cortical networks Cerebral Cortex 22:1894-1903
Mars RB, Jbabdi S, Sallet J, O'Reilly JX, Croxson PL, Olivier E, Noonan MP, Bergmann C, Mitchell AS, Baxter MG, Behrens TEJ, Johansen-Berg H, Tomassini V, Miller KL, & Rushworth MFS (2011) Diffusion-weighted imaging tractography-based parcellation of the human parietal cortex and comparison with human and macaque resting state functional connectivity. Journal of Neuroscience 31:4087-4100


Between-species comparisons

How do we compare brains of different species? Brains of different mammals differ vastly in size, number of areas, and connections. We have developed what we call the 'common space approach', a framework of studying brain organization in terms of abstact features spaces that can be directly compared between species.

Core papers on the common space approach:

Mars RB, Jbabdi S, & Rushworth MFS (2021) A common space approach to comparative neuroscience Annual Reviews of Neuroscience 44:69-86
Eichert N, Robinson EC, Bryant KL, Jbabdi S, Jenkinson M, Li L, Krug K, Watkins KE, & Mars RB (2020) Cross-species cortical alignment identifies different types of anatomical reorganization in the primate temporal. eLife 9:e53232
Mars RB, Sotiropoulos SN, Passingham RE, Sallet J, Verhagen L Khrapitchev AA, Sibons NS, & Jbabdi S (2018) Whole brain comparative anatomy using connectivity blueprints. eLife 7:e35237
Mars RB, Verhagen L, Gladwin TE, Neubert FX, Sallet J, & Rushworth MFS (2016) Comparing brains by matching connectivity profiles. Neuroscience and Biobehavioral Reviews 60:90-97

Key comparative studies:

Roumazeilles L, Eichert N, Bryant KL, Folloni D, Sallet J, Vijayakumar S, Foxley S, Tendler BC, Jbabdi S, Reveley C, Verhagen L, Dershowitz LB, Guthrie M, Flach E, Miller KL, & Mars RB (2020) Longitudinal connections and the organization of the temporal cortex in macaques, great apes, and humans. PLoS Biology 18:e3000810
Balsters JH, Zerbi V, Sallet S, Wenderoth N, & Mars RB (2020) Primate homologs of mouse cortico-striatal circuits. eLife 9:e53680
Folloni D, Sallet J, Khrapitchev AA, Sibson NR, Verhagen L, & Jbabdi S (2019) Dichotomous organization of amygdala/temporal-prefrontal bundles in both humans and monkeys. eLife 8:e47175
Mars RB, Sallet J, Neubert FX, & Rushworth MFS (2013) Connectivity profiles reveal the relationship between brain areas for social cognition in human and monkey temporoparietal cortex. Proceedings of the National Academy of Sciences USA 110:10806-10811


What does it do?

Our brain differs dramatically from that of other primates. It is larger overall, some areas have expanded disproportionally, and the connections between areas have changed. These differences are paralleled by differences in our behavioral repertoire. The ultimate goal of our research is to understand how differences in brain organization are related to differences in behaviour and how this has been driven by the evolutionary challenges that different lineages in the animal kingdom have faced, with the human as a special case. To date, this research has focused mostly on how social abilities, including communication through spoken language, and foraging niche are related to their brain organization. Moreover, we look at how individual differences between people's behavior in these domains relate to differences in their brain organization.

What makes the human brain different?

Mars RB, Eichert N, Jbabdi S, Verhagen L, & Rushworth MFS (2018) Connectivity and the search for specializations in the language-capable brain. Current Opinion in Behavioral Sciences 21:19-26
Mars RB, Passingham RE, Neubert FX, Verhagen L, & Sallet J (2017) Evolutionary specializations of human association cortex. In: Kaas JH (Ed.) Evolution of Nervous Systems (2nd edition, vol. 4), pp. 185-205. Oxford: Elsevier

Relevant publications on the relationship between brain organization and social abilities:

Schurz M, Radue J, Tholen MG, Maliske L, Margulies DS, Mars RB, Sallet J, & Kanske P (2021) Towards a hierarchical model of social cognition: A neuroimaging meta-analysis and integrative review of empathy and Theory of Mind. Psychological Bulletin 147:293-327
Noonan MP, Sallet J, Mars RB, Neubert FX, O'Reilly JX, Andersson JL, Mitchell AS, Bell AH, & Rushworth MFS (2014) A neural circuit covarying with social hierarchy in macaque. PLoS Biology 12:e1001940
Brazil IA, Hunt LT, Bulten BH, Kessels RPC, De Bruijn ERA, & Mars RB (2013) Psychopathy-related traits and the use of reward and social information: A computational approach. Frontiers in Psychology 4:952
Rushworth MFS, Mars RB, & Sallet J (2013) Are there specialized circuits for social cognition and are they unique to humans? Current Opinion in Neurobiology 23:436-442
Mars RB, Neubert FX, Noonan MP, Sallet J, Toni I, & Rushworth MFS (2012) On the relationship between the 'default mode network' and the 'social brain'. Frontiers in Human Neuroscience 6:189
Sallet J, Mars RB, Noonan MP, Andersson J, O'Reilly JX, Jbabdi S, Croxson PL, Miller KL, Jenkinson M, & Rushworth MFS (2011) Social network size affects neural circuits in macaques. Science 334:697-700

Relevant publications on the relationship between brain organization and foraging:

Kolling N, Wittmann MK, Behrens TEJ, Boorman ED, Mars RB, & Rushworth MFS (2016) Value, search, persistence and model updating in anterior cingulate cortex. Nature Neuroscience 10:1280-1285
Rushworth MFS, Kolling N, Sallet J, & Mars RB (2012) Valuation and decision-making in frontal cortex: One or many serial or parallel systems? Current Opinion in Neurobiology 22:946-955
Kolling N, Behrens TEJ, Mars RB, & Rushworth MFS (2012) Neural mechanisms of foraging. Science 336:95-98