title: Neural representation of task difficulty and decision making during perceptual categorization: a timing diagram.
abstract: When does the brain know that a decision is difficult to make? How does decision difficulty affect the allocation of neural resources and timing of constituent cortical processing? Here, we use single-trial analysis of electroencephalography (EEG) to identify neural correlates of decision difficulty and relate these to neural correlates of decision accuracy. Using a cued paradigm, we show that we can identify a component in the EEG that reflects the inherent task difficulty and not simply a correlation with the stimulus. We find that this decision difficulty component arises approximately 220 ms after stimulus presentation, between two EEG components that are predictive of decision accuracy [an "early" (170 ms) and a "late" (approximately 300 ms) component]. We use these results to develop a timing diagram for perceptual decision making and relate the component activities to parameters of a diffusion model for decision making.
authors.affiliation: Laboratory for Intelligent Imaging and Neural Computing, Department of Biomedical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: Marios G
authors.initials: MG
authors.lastname: Philiastides
authors.forename: Roger
authors.initials: R
authors.lastname: Ratcliff
authors.forename: Paul
authors.initials: P
authors.lastname: Sajda
mesh_terms: D000328:Adult; D001336:Automobiles; D002540:Cerebral Cortex / Q000502:physiology*; D003463:Cues; D003657:Decision Making / Q000502:physiology*; D004192:Discrimination, Psychological; D004569:Electroencephalography; D005071:Evoked Potentials; D005145:Face; D005260:Female; D006801:Humans; D008297:Male; D008960:Models, Psychological; D010775:Photic Stimulation / Q000379:methods; D011237:Predictive Value of Tests; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology*