Neuroscience 2005 Abstract
| Presentation Number: | 934.1 |
|---|---|
| Abstract Title: | The timing of EEG components indicative of stimulus evidence during perceptual decision-making. |
| Authors: |
Philiastides, M. G.*1
; Sajda, P.1
1Biomedical Engineering, Columbia Univ., New York, NY |
| Primary Theme and Topics |
Cognition and Behavior - Human Cognition, Behavior, and Anatomy -- Perception and imagery |
| Session: |
934. Perception and Imagery V Slide |
| Presentation Time: | Wednesday, November 16, 2005 1:00 PM-1:15 PM |
| Location: | Washington Convention Center - Room 144A |
| Keywords: |
Previously, using a face vs car categorization task and single-trial EEG analysis, we reported the existence of two discriminating EEG components which resulted in neurometric functions that can account for psychophysical performance (Philiastides and Sajda, SFN 2004). Though the earliest component was shown to be consistent with the well-known N170, the later component (~300ms) was the best match to the psychophysical data. We proposed that the early component is linked to early visual perception whereas the late component is likely to reflect post-sensory processing (i.e. decision) stages.
In order to characterize the neural correlates of task difficulty and possibly describe the decision uncertainty, we repeat these experiments and use our single-trial linear discriminator to compare trials at different levels of stimulus evidence (i.e. different % phase coherence levels). We observe a maximally discriminating component that is situated between the early and late components (i.e. it occurs at ~250 ms post-stimulus). The component appears to be stimulus-locked and its temporal onset remains unchanged for different coherence levels. The component is most pronounced when the discrimination is between the highest and lowest coherence levels. Interestingly however, for some subjects, it remains statistically significant even between cases that resulted in as little as 5% difference in psychophysical performance. The component is always present regardless of whether the discrimination is performed only for 1) face, 2) car, or 3) face and car trials combined. We also determine sensor projections that indicate a spatial component distribution at centrofrontal as well as several occipitoparietal sites. We show that this component is clearly correlated with stimulus evidence and may in fact reflect an assessment of task difficulty. We emphasize the importance of investigating its temporal relationship to the two components predictive of psychophysical performance and the potential implication of its timing for developing models of the perceptual decision making process.
In order to characterize the neural correlates of task difficulty and possibly describe the decision uncertainty, we repeat these experiments and use our single-trial linear discriminator to compare trials at different levels of stimulus evidence (i.e. different % phase coherence levels). We observe a maximally discriminating component that is situated between the early and late components (i.e. it occurs at ~250 ms post-stimulus). The component appears to be stimulus-locked and its temporal onset remains unchanged for different coherence levels. The component is most pronounced when the discrimination is between the highest and lowest coherence levels. Interestingly however, for some subjects, it remains statistically significant even between cases that resulted in as little as 5% difference in psychophysical performance. The component is always present regardless of whether the discrimination is performed only for 1) face, 2) car, or 3) face and car trials combined. We also determine sensor projections that indicate a spatial component distribution at centrofrontal as well as several occipitoparietal sites. We show that this component is clearly correlated with stimulus evidence and may in fact reflect an assessment of task difficulty. We emphasize the importance of investigating its temporal relationship to the two components predictive of psychophysical performance and the potential implication of its timing for developing models of the perceptual decision making process.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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