Neuroscience 2003 Abstract
| Presentation Number: | 515.2 |
|---|---|
| Abstract Title: | Attentional contributions to visual processing of symmetry. |
| Authors: |
Conte, M. M.*1
; Purpura, K. P.1
; Victor, J. D.1
1Neurol. and Neurosci., Weill Med. Col. of Cornell Univ., New York, NY |
| Primary Theme and Topics |
Cognition and Behavior - Human Cognition and Behavior -- Attention |
| Session: |
515. Attention III Poster |
| Presentation Time: | Monday, November 10, 2003 2:00 PM-3:00 PM |
| Location: | Morial Convention Center - Hall F-I, Board # V2 |
| Keywords: | OBJECT RECOGNITION, TEMPORAL, PSYCHOPHYSICS |
Previously (SFN, 2002) we showed that processing of vertical-axis mirror symmetry (V) is not consistent with either a pure parallel or serial model, and is more efficient along the vertical midline than off-axis. Here we extend the analysis to horizontal (H) symmetry, to determine the generality and basis of these observations.
Each stimulus consisted of four 8x8 arrays of black and white checks. Three of the arrays (distractors) were colored at random; in the fourth array (the target), bilateral symmetry was introduced in a graded fashion. We measured fraction correct (FC) and reaction time in a 4-AFC task. Trained observers (N=4) viewed these stimuli in single-symmetry blocks (V or H), and in mixed blocks (V and H). The four arrays were positioned 4 deg from fixation along the cardinal axes, and presented for durations of either 100 or 400 ms. In single-symmetry blocks, an RSVP mode (SFN, 2002) was also employed (100 ms per stimulus, 50 ms ISIs).
In many respects, V and H symmetry results were similar: FC in RSVP was higher than FC for simultaneous presentation at 100 ms, but not as high as FC for simultaneous presentation at 400 ms. In RSVP mode, FC was highest when the target was presented first. A masking effect was seen at 200 ms followed by recovery of sensitivity at 300 and 400 ms. Errors were not temporally random. When wrong, subjects usually chose a distractor immediately preceding or following the target. However, the spatial error patterns were distinctive. For V-only blocks, FC was highest along the vertical midline of the display. For H-only blocks, FC was highest along the horizontal midline. In mixed blocks, the error pattern was intermediate.
We conclude that stimulus expectation guides the focal attention scanning strategy employed when processing bilateral symmetry. In particular, stimulus expectation enhances processing of vertical symmetry on the vertical midline, and horizontal symmetry on the horizontal midline.
Each stimulus consisted of four 8x8 arrays of black and white checks. Three of the arrays (distractors) were colored at random; in the fourth array (the target), bilateral symmetry was introduced in a graded fashion. We measured fraction correct (FC) and reaction time in a 4-AFC task. Trained observers (N=4) viewed these stimuli in single-symmetry blocks (V or H), and in mixed blocks (V and H). The four arrays were positioned 4 deg from fixation along the cardinal axes, and presented for durations of either 100 or 400 ms. In single-symmetry blocks, an RSVP mode (SFN, 2002) was also employed (100 ms per stimulus, 50 ms ISIs).
In many respects, V and H symmetry results were similar: FC in RSVP was higher than FC for simultaneous presentation at 100 ms, but not as high as FC for simultaneous presentation at 400 ms. In RSVP mode, FC was highest when the target was presented first. A masking effect was seen at 200 ms followed by recovery of sensitivity at 300 and 400 ms. Errors were not temporally random. When wrong, subjects usually chose a distractor immediately preceding or following the target. However, the spatial error patterns were distinctive. For V-only blocks, FC was highest along the vertical midline of the display. For H-only blocks, FC was highest along the horizontal midline. In mixed blocks, the error pattern was intermediate.
We conclude that stimulus expectation guides the focal attention scanning strategy employed when processing bilateral symmetry. In particular, stimulus expectation enhances processing of vertical symmetry on the vertical midline, and horizontal symmetry on the horizontal midline.
Supported by EY7977
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2003 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2003. Online.
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