title: Evidence accumulation detected in BOLD signal using slow perceptual decision making.
abstract: BACKGROUND
  We assessed whether evidence accumulation could be observed in the BOLD signal during perceptual decision making. This presents a challenge since the hemodynamic response is slow, while perceptual decisions are typically fast.
  
  
  METHODS
  Guided by theoretical predictions of the drift diffusion model, we slowed down decisions by penalizing participants for incorrect responses. Second, we distinguished BOLD activity related to stimulus detection (modeled using a boxcar) from activity related to integration (modeled using a ramp) by minimizing the collinearity of GLM regressors. This was achieved by dissecting a boxcar into its two most orthogonal components: an "up-ramp" and a "down-ramp." Third, we used a control condition in which stimuli and responses were similar to the experimental condition, but that did not engage evidence accumulation of the stimuli.
  
  
  RESULTS
  The results revealed an absence of areas in parietal cortex that have been proposed to drive perceptual decision making but have recently come into question; and newly identified regions that are candidates for involvement in evidence accumulation.
  
  
  METHODS
  Previous fMRI studies have either used fast perceptual decision making, which precludes the measurement of evidence accumulation, or slowed down responses by gradually revealing stimuli. The latter approach confounds perceptual detection with evidence accumulation because accumulation is constrained by perceptual input.
  
  
  CONCLUSIONS
  We slowed down the decision making process itself while leaving perceptual information intact. This provided a more sensitive and selective observation of brain regions associated with the evidence accumulation processes underlying perceptual decision making than previous methods.
authors.affiliation: Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08544, USA. Electronic address: paul.m.krueger@berkeley.edu.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Krueger
authors.affiliation: Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08544, USA. Electronic address: m.k.van.vugt@rug.nl.
authors.forename: Marieke K
authors.initials: MK
authors.lastname: van Vugt
authors.affiliation: Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08544, USA. Electronic address: psimen@oberlin.edu.
authors.forename: Patrick
authors.initials: P
authors.lastname: Simen
authors.affiliation: Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08544, USA. Electronic address: nystrom@princeton.edu.
authors.forename: Leigh
authors.initials: L
authors.lastname: Nystrom
authors.affiliation: Department of Mechanical and Aerospace Engineering and Program in Applied and Computational Mathematics; Associated Faculty in Neuroscience, Princeton University, Princeton, NJ, 08544, USA. Electronic address: pholmes@math.princeton.edu.
authors.forename: Philip
authors.initials: P
authors.lastname: Holmes
authors.affiliation: Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08544, USA. Electronic address: jdc@princeton.edu.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Cohen
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003657:Decision Making / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D030141:Feedback, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D007600:Judgment / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009039:Motion Perception / Q000502:physiology; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood*; D012044:Regression Analysis; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Decision making; Drift-diffusion model; Evidence accumulation; Functional magnetic resonance imaging