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The Journal of Neuroscience, August 30, 2006, 26(35):8965-8975; doi:10.1523/JNEUROSCI.1655-06.2006

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Behavioral/Systems/Cognitive
Neural Representation of Task Difficulty and Decision Making during Perceptual Categorization: A Timing Diagram

Marios G. Philiastides,¹ Roger Ratcliff,² and Paul Sajda¹

¹Laboratory for Intelligent Imaging and Neural Computing, Department of Biomedical Engineering, Columbia University, New York, New York 10027, and ²Department of Psychology, Ohio State University, Columbus, Ohio 43210

Correspondence should be addressed to Dr. Paul Sajda at the above address. Email: ps629{at}columbia.edu

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 220 ms after stimulus presentation, between two EEG components that are predictive of decision accuracy [an "early" (170 ms) and a "late" (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.

Key words: task difficulty; decision making; electroencephalography (EEG); single-trial analysis; diffusion model; timing diagram

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Received April 18, 2006; revised July 12, 2006; accepted July 13, 2006.

Correspondence should be addressed to Dr. Paul Sajda at the above address. Email: ps629{at}columbia.edu

This article has been cited by other articles:

				M. G. Philiastides and P. Sajda EEG-Informed fMRI Reveals Spatiotemporal Characteristics of Perceptual Decision Making J. Neurosci., November 28, 2007; 27(48): 13082 - 13091. [Abstract] [Full Text] [PDF]

				R. Ratcliff and G. McKoon The Diffusion Decision Model: Theory and Data for Two-Choice Decision Tasks Neural Comput., April 1, 2007; 20(4): 873 - 922. [Abstract] [Full Text] [PDF]

				B. Pleger, C. C. Ruff, F. Blankenburg, S. Bestmann, K. Wiech, K. E. Stephan, A. Capilla, K. J. Friston, and R. J. Dolan Neural Coding of Tactile Decisions in the Human Prefrontal Cortex J. Neurosci., November 29, 2006; 26(48): 12596 - 12601. [Abstract] [Full Text] [PDF]

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