title: Chronotype Modulates Language Processing-Related Cerebral Activity during Functional MRI (fMRI).
abstract: OBJECTIVE
  Based on individual daily physiological cycles, humans can be classified as early (EC), late (LC) and intermediate (IC) chronotypes. Recent studies have verified that chronotype-specificity relates to performance on cognitive tasks: participants perform more efficiently when tested in the chronotype-specific optimal time of day than when tested in their non-optimal time. Surprisingly, imaging studies focussing on the underlying neural mechanisms of potential chronotype-specificities are sparse. Moreover, chronotype-specific alterations of language-related semantic processing have been neglected so far.
  
  
  METHODS
  16 male, healthy ECs, 16 ICs and 16 LCs participated in a fast event-related functional Magnetic Resonance Imaging (fMRI) paradigm probing semantic priming. Subjects read two subsequently presented words (prime, target) and were requested to determine whether the target word was an existing word or a non-word. Subjects were tested during their individual evening hours when homeostatic sleep pressure and circadian alertness levels are high to ensure equal entrainment.
  
  
  RESULTS
  Chronotype-specificity is associated with task-performance and brain activation. First, ECs exhibited slower reaction times than LCs. Second, ECs showed attenuated BOLD responses in several language-related brain areas, e.g. in the left postcentral gyrus, left and right precentral gyrus and in the right superior frontal gyrus. Additionally, increased BOLD responses were revealed for LCs as compared to ICs in task-related areas, e.g. in the right inferior parietal lobule and in the right postcentral gyrus.
  
  
  CONCLUSIONS
  These findings reveal that even basic language processes are associated with chronotype-specific neuronal mechanisms. Consequently, results might change the way we schedule patient evaluations and/or healthy subjects in e.g. experimental research and adding "chronotype" as a statistical covariate.
authors.affiliation: Institute of Neuroscience and Medicine (INM- 4), Medical Imaging Physics, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany; JARA, Translational Brain Medicine, RWTH Aachen University, 52074, Aachen, Germany; Department of Neurology, University Clinic Aachen, 52074, Aachen, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Rosenberg
authors.affiliation: Institute of Neuroscience and Medicine (INM- 4), Medical Imaging Physics, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Reske
authors.affiliation: Institute of Neuroscience and Medicine (INM- 4), Medical Imaging Physics, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
authors.forename: Tracy
authors.initials: T
authors.lastname: Warbrick
authors.affiliation: Institute of Neuroscience and Medicine (INM- 4), Medical Imaging Physics, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany; JARA, Translational Brain Medicine, RWTH Aachen University, 52074, Aachen, Germany; Department of Neurology, University Clinic Aachen, 52074, Aachen, Germany.
authors.forename: N J
authors.initials: NJ
authors.lastname: Shah
mesh_terms: D000328:Adult; D001683:Biological Clocks; D001931:Brain Mapping; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010296:Parietal Lobe / Q000502:physiology*; D011930:Reaction Time; D013003:Somatosensory Cortex / Q000502:physiology*; D013060:Speech; D013067:Speech Perception; D055815:Young Adult