Tsubomi,H., Ikeda, T., & Osaka, N.
Title:
Primary visual cortex scales individual’s perceived brightness with
power function: Inner psychophysics with fMRI.
Journal:
Journal of Experimental Psychology: Human Perception & Performance
doi:
10.1037/a0030025
論文URL:
http://www.apa.org/pubs/journals/xhp/index.aspx
Abstract:
Perceived brightness is well described by Stevens’ power function (S. S.
Stevens, 1957, On the psychophysical law, Psychological Review, Vol. 64,
pp. 153-181), with a power exponent of .33 (the cubic-root function of
luminance). The power exponent actually varies across individuals, yet
little is known about neural substrates underlying this individual
difference. The present functional MRI study investigated how neural
activation levels in the visual cortex serve to scale individual’s
subjective brightness. Participants rated brightness of a disk ranging
from 1- to 100-cd/m(2) luminance. Subjective brightness ratings showed
an almost perfect log-linear dependence on luminance intensity, with the
power exponent averaging .32. The fMRI results showed that activity in
the bilateral primary visual cortex along with the calcarine sulcus
(also known as Brodmann’s area 17 and VI) increased log-linearly with
physical luminance, showing average power exponents of .32 and .27 in
the left and right hemispheres, respectively. There were substantial
individual variations in the power function exponents for both
subjective brightness ratings (.14 to .46) and primary visual cortex
activation (.12 to .55). An important finding was that 2 power exponents
were closely correlated (r = .62). Subjective brightness ratings and
primary visual cortex activation were both better correlated with
stimulus luminance than stimulus contrast (at the border of the
stimulus). These results suggest that primary visual cortex activation
can scale individual’s subjective brightness in accordance with Stevens’
power law.
著者Contact先の email:
htsubomi@fennel.rcast.u-tokyo.ac.jp
- 投稿タグ
- IntJnlPaper
