The Journal of Neuroscience, June 15, 2001, 21(12):4490-4497
Influence of the Direction of Elemental Luminance Gradients on
the Responses of V4 Cells to Textured Surfaces
Akitoshi
Hanazawa and
Hidehiko
Komatsu
Laboratory of Neural Control, National Institute for Physiological
Sciences, Myodaiji, Okazaki, Aichi 444-8585, Japan
The texture of an object provides important cues for its
recognition; however, little is known about the neural representation of texture. To investigate the representation of texture in the visual
cortex, we recorded single-cell activities in area V4 of macaque
monkeys. To distinguish the sensitivity of the cells to texture
parameters such as density and element size from that to spatial
frequency, we used texture stimuli mimicking shaded granular surfaces.
We varied the size and density of the texture elements and the
direction of elemental luminance gradients (apparent shadings) as
stimulus parameters. Most macaque V4 cells (151 of 170; 89%) exhibited
sensitivity to the texture parameters. Interestingly, 21of these cells
were tuned to single shading directions (unidirectional tuning). This
unidirectional tuning cannot be explained by complex-cell-like tuning
for spectral power of spatial frequency, because texture stimuli with a
shading direction and its opposite have almost the same spectral power.
Unidirectional tunings of these cells were invariant for the position
of the texture elements. Thus, this tuning cannot be explained by
simple-cell-like phase-dependent spatial frequency tuning or
selectivity to a particular arrangement of the elements. Moreover, the
unidirectional tuning had a bias toward vertical directions, consistent
with an anisotropy in the perception of three-dimensional shape
from shading. This novel spatial property suggests that V4 cells are
involved in extracting texture features from objects, including their
three-dimensionality.
Key words:
texture; density; shape from shading; monkey; visual
cortex; V4
Copyright © 2001 Society for Neuroscience 0270-6474/01/21124490-08$05.00/0
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