August 2009
Volume 9, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Attention improves response reliability by decreasing noise: Reduction in the amplitude of fluctuations of fMRI signal at non-stimulus frequencies using periodic retinotopic mapping stimuli
Author Affiliations
  • David Bressler
    School of Optometry, University of California, Berkeley
  • Michael Silver
    School of Optometry, University of California, Berkeley, and Helen Wills Neuroscience Institute, University of California, Berkeley
Journal of Vision August 2009, Vol.9, 221. doi:10.1167/9.8.221
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      David Bressler, Michael Silver; Attention improves response reliability by decreasing noise: Reduction in the amplitude of fluctuations of fMRI signal at non-stimulus frequencies using periodic retinotopic mapping stimuli. Journal of Vision 2009;9(8):221. doi: 10.1167/9.8.221.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 

Visual spatial attention could enhance the neural representation of a stimulus by amplifying the response to the stimulus and/or by suppressing sources of noise. In this study we show that attention improves the reliability of fMRI responses to a periodic rotating wedge checkerboard stimulus through both an increase in signal strength and a decrease in noise. On separate runs, attention was continuously directed either to the wedge stimulus or to the central fixation point. In both attention conditions, subjects performed a difficult contrast decrement detection task, and task difficulty and the physical stimuli were equated in the two conditions. Fourier analysis was performed on fMRI time series in retinotopic visual cortical areas (V1, V2, V3, V3A/B, V4, V7) as well as in intraparietal cortical areas that contain topographic maps of visual spatial attention (IPS1 and IPS2). Relative to the attention to fixation condition, attending to the wedge stimulus increased the amplitude of the response at the temporal frequency corresponding to the stimulus cycle (0.03 Hz). This enhancement of stimulus signal by attention was observed across all identified cortical areas. We also analyzed fluctuations in other temporal frequency bands that did not correspond to the stimulus cycle and therefore represent noise in the fMRI response. In cortical areas higher in the visual hierarchy, attending to the stimulus reduced the amplitude of fluctuations in these non-stimulus frequencies. In conclusion, attending to a stimulus can improve reliability of cortical fMRI responses by enhancing the stimulus signal and by decreasing noise.

 
Bressler, D. Silver, M. (2009). Attention improves response reliability by decreasing noise: Reduction in the amplitude of fluctuations of fMRI signal at non-stimulus frequencies using periodic retinotopic mapping stimuli [Abstract]. Journal of Vision, 9(8):221, 221a, http://journalofvision.org/9/8/221/, doi:10.1167/9.8.221. [CrossRef]
Footnotes
 We wish to thank Joanna Tung for her help in data analysis.
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