The Richness of Task-Evoked Hemodynamic Responses Defines a Pseudohierarchy of Functionally Meaningful Brain Networks

Cereb Cortex. 2015 Sep;25(9):2658-69. doi: 10.1093/cercor/bhu064. Epub 2014 Apr 11.

Abstract

Functional magnetic resonance imaging can measure distributed and subtle variations in brain responses associated with task performance. However, it is unclear whether the rich variety of responses observed across the brain is functionally meaningful and consistent across individuals. Here, we used a multivariate clustering approach that grouped brain regions into clusters based on the similarity of their task-evoked temporal responses at the individual level, and then established the spatial consistency of these individual clusters at the group level. We observed a stable pseudohierarchy of task-evoked networks in the context of a delayed sequential motor task, where the fractionation of networks was driven by a gradient of involvement in motor sequence preparation versus execution. In line with theories about higher-level cognitive functioning, this gradient evolved in a rostro-caudal manner in the frontal lobe. In addition, parcellations in the cerebellum and basal ganglia matched with known anatomical territories and fiber pathways with the cerebral cortex. These findings demonstrate that subtle variations in brain responses associated with task performance are systematic enough across subjects to define a pseudohierarchy of task-evoked networks. Such networks capture meaningful functional features of brain organization as shaped by a given cognitive context.

Keywords: clustering analysis; fMRI; functional connectivity; motor preparation and execution; multiscale task-evoked networks.

MeSH terms

  • Adult
  • Brain / blood supply*
  • Brain / physiology*
  • Brain Mapping*
  • Cluster Analysis
  • Female
  • Hemodynamics / physiology*
  • Humans
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging
  • Male
  • Models, Neurological
  • Neural Pathways / blood supply*
  • Neural Pathways / physiology*
  • Oxygen / blood
  • Psychomotor Performance / physiology
  • Young Adult

Substances

  • Oxygen