November 2002
Volume 2, Issue 7
Free
Vision Sciences Society Annual Meeting Abstract  |   November 2002
Effect of band-pass filtered noise on cortical face responses
Author Affiliations
  • Topi Tanskanen
    Helsinki University of Technology, Finland
  • Risto Näsänen
    Institute of Occupational Health, Finland
  • Teresa Montez
    Helsinki University of Technology, Finland
  • Juha Päällysaho
    Helsinki University of Technology, Finland
  • Riitta Hari
    Helsinki University of Technology, Finland
Journal of Vision November 2002, Vol.2, 599. doi:10.1167/2.7.599
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      Topi Tanskanen, Risto Näsänen, Teresa Montez, Juha Päällysaho, Riitta Hari; Effect of band-pass filtered noise on cortical face responses. Journal of Vision 2002;2(7):599. doi: 10.1167/2.7.599.

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

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Abstract

Psychophysical studies have shown that the human face recognition system utilizes only a limited band of the spatial frequencies (sfs) present in facial images. To find cortical responses that would show a similar tuning, we recorded whole-scalp neuromagnetic responses to facial images that contained narrow-band spatial noise (10 noise bands with central sfs from 2 to 45 c/image). The signal-to-noise ratio was 0.74 across all sfs and made recognition impossible around the 16 c/image condition, but easy in the low and high sf conditions. The stimuli (7×7 deg2, mean luminance 130 cd/m2, RMS contrast 0.174) appeared abruptly on an average gray background for 0.5 s once every 2.5 s, and stimuli with different noise sfs were presented in random order. The subject had to respond to an image of a target person. In the six subjects, the strongest modulation by noise sf occurred in the 150–200 ms temporo-occipital responses: The largest signals were elicited by the noiseless and lowest-sf noise stimuli. The signals decreased as a function of increasing noise sf until they disappeared at the medium sfs, and increased again at the highest frequencies. For different subjects, the U-shaped tuning curve had a minimum at 5.6–23 c/image, and a bandwidth of 2–3 octaves. The sustained 250–650 ms response in the same cortical area was modulated less. The 80–110 ms midoccipital responses showed a different pattern, being weak for the lowest noise sfs, then increasing as a function of sf, and attenuating at the highest noise sfs. In conclusion, these results show that the 150–200 ms temporo-occipital response resembles behavioral face recognition in its sensitivity to noise sf. Thus it could reflect processes that are critical for the recognition of faces.

Tanskanen, T., Näsänen, R., Montez, T., Päällysaho, J., Hari, R.(2002). Effect of band-pass filtered noise on cortical face responses [Abstract]. Journal of Vision, 2( 7): 599, 599a, http://journalofvision.org/2/7/599/, doi:10.1167/2.7.599. [CrossRef]
Footnotes
 Supported by the Academy of Finland and the EU's Large-Scale Facility Neuro-BIRCH III at BRU, LTL, HUT.
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