Research interests


I am interested in why our brain is organized the way it is. Specifically, I am 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. To date, I have mostly focused on one particular aspect of brain organization--connectivity. I try to understand how areas of the brain are connected, why they are connected in that way, and how their interactions are related to behaviour. I employ a wide range of experimental techniques to try to understand these processes.

Roughly, my research concentrates around three themes that represent the who, how, and why of brain organization:

  • Who? Or: What brain regions can we find and what is the architecture of connections between them?
  • How? Or: How does activity in one brain region influence activity in another?
  • Why? Or: Why is the brain organized the way it is?


    Who?

    This part of my research is aimed at mapping areas of the brain in humans and non-human primates and to investigate the connections between these areas. The connections of brain regions constrain their inputs and output and thus give us vital clues about their function. I use diffusion-weighted imaging and resting state functional MRI to study the architecture of connections between brain areas and have developed a number of ways to compare these architectures between species.

    Relevant publications:

  • Neubert FX et al. (2015) Connectivity reveals relationship of brain areas for reward-guided learning and decision making in human and monkey frontal cortex. Proc Natl Acad Sci USA 112:E2695-E2704

  • Neubert FX et al. (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 et al. (2013) The organization of dorsal frontal cortex in humans and macaques. J Neurosci 33:12255-12274

  • Mars RB et al. (2013) Connectivity profiles reveal the relationship between brain areas for social cognition in human and monkey temporoparietal cortex. Proc Natl Acad Sci USA 110:10806-10811

  • Mars RB et al. (2012) Connectivity-based subdivisions of the human right 'temporoparietal junction area' (TPJ): Evidence for different areas participating in different cortical networks. Cereb Cortex 22:1894-1903

  • Mars RB et al. (2011) Diffusion-weighted imaging tractography-based parcellation of the human parietal cortex and comparison with human and macaque resting state functional connectivity. J Neurosci 31:4087-4100

  • Rushworth MFS, Boorman E, & Mars RB (2009) Comparing brain connections in different species using diffusion weighted imaging. In: Johansen-Berg H & Behrens TEJ (Eds.) Diffusion MRI: From quantitative measurement to in vivo neuroanatomy, pp. 445-460. Amsterdam: Academic Press

  • How?

    I use functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) to investigate how regions of the human brain influence activity in other regions while people perform tasks and to study the relationship between these interactions and structural connections in the brain. In most studies, we have looked at the situation where people abandon an action plan in favour of an alternative, so-called action reprogramming. In more recent research we have also looked at the effects of white matter lesions on the interactions between brain areas.

    Relevant publications:

  • Tavor I et al. (2016) Task-free MRI predicts individual differences in brain activity during task performance. Science 352:216-220

  • Johnen V et al. (2015) Causal manipulation of functional connectivity in a specific neural pathway during behaviour and at rest. eLife 4:e04585

  • Van Campen AD et al. (2013) Paired-pulse transcranial magnetic stimulation reveals probability-dependent changes in functional connectivity between right inferior frontal cortex and primary motor cortex during go/no-go performance. Front Hum Neurosci 7:736

  • O'Reilly JX et al. (2013) A causal effect of disconnection lesions on interhemispheric functional connectivity in rhesus monkeys. Proc Natl Acad Sci USA 110:13982-13987

  • Mars RB, Neubert FX, & Rushworth MFS (2011) Top-down control over the motor cortex. In: Mars RB et al. (Eds.) Neural basis of motivational and cognitive control, pp. 111-125. Cambridge: MIT Press

  • Neubert FX et al. (2010) Cortical and subcortical interactions during action reprogramming and their related white matter pathways. Proc Natl Acad Sci USA 107:13240-13245

  • Mars RB et al. (2009) Short-latency influence of medial frontal cortex on primary motor cortex during action selection under conflict. J Neurosci 29:6926-6931

  • Mars RB et al. (2007) On the programming and reprogramming of actions. Cereb Cortex 28:2972-2979

  • Why?

    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 my 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. To date, this research has focused mostly on how primates' social abilities and foraging niche are related to their brain organization. Moreover, I look at how individual differences between people's behavior in these domains relate to differences in their brain organization.

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

  • Noonan MP et al. (2014) A neural circuit covarying with social hierarchy in macaque. PLoS Biol 12:e1001940

  • Brazil IA et al. (2013) Psychopathy-related traits and the use of reward and social information: A computational approach. Front Psychol 4:952

  • Rushworth MFS, Mars RB, & Sallet J (2013) Are there specialised circuits for social cognition and are they unique to humans? Curr Opin Neurobiol 23:436-442

  • Mars RB et al. (2012) On the relationship between the 'default mode network' and the 'social brain'. Front Human Neurosci 6:189

  • Sallet J et al. (2011) Social network size affects neural circuits in macaques. Science 334:697-700

    Relevant publications on the relationship between brain organization and foraging:

  • Rushworth MFS et al. (2012) Valuation and decision-making in frontal cortex: One or many serial or parallel systems? Curr Opin Neurobiol 22:946-955

  • Kolling N et al. (2012) Neural mechanisms of foraging. Science 336:95-98

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