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The extraction of 3D shape from texture and shading in the human brain.

Georgieva SS, Todd JT, Peeters R, Orban GA - Cereb. Cortex (2008)

Bottom Line: The results of both passive and active experiments reveal that the extraction of 3D SfT involves the bilateral caudal inferior temporal gyrus (caudal ITG), lateral occipital sulcus (LOS) and several bilateral sites along the intraparietal sulcus.Additional results from psychophysical experiments reveal that this difference in neuronal substrate cannot be explained by a difference in strength between the 2 cues.These results underscore the importance of the posterior part of the lateral occipital complex for the extraction of visual 3D shape information from all depth cues, and they suggest strongly that the importance of shading is diminished relative to other cues for the analysis of 3D shape in parietal regions.

View Article: PubMed Central - PubMed

Affiliation: Laboratorium voor Neuro- en Psychofysiologie, Katholieke Universiteit Leuven School of Medicine, Campus Gasthuisberg, B-3000 Leuven, Belgium.

ABSTRACT
We used functional magnetic resonance imaging to investigate the human cortical areas involved in processing 3-dimensional (3D) shape from texture (SfT) and shading. The stimuli included monocular images of randomly shaped 3D surfaces and a wide variety of 2-dimensional (2D) controls. The results of both passive and active experiments reveal that the extraction of 3D SfT involves the bilateral caudal inferior temporal gyrus (caudal ITG), lateral occipital sulcus (LOS) and several bilateral sites along the intraparietal sulcus. These areas are largely consistent with those involved in the processing of 3D shape from motion and stereo. The experiments also demonstrate, however, that the analysis of 3D shape from shading is primarily restricted to the caudal ITG areas. Additional results from psychophysical experiments reveal that this difference in neuronal substrate cannot be explained by a difference in strength between the 2 cues. These results underscore the importance of the posterior part of the lateral occipital complex for the extraction of visual 3D shape information from all depth cues, and they suggest strongly that the importance of shading is diminished relative to other cues for the analysis of 3D shape in parietal regions.

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3D SfS sensitive regions (control experiment 2, fixed effect, n = 6). (A) Shading specific areas significantly (P < 0.05 corrected) activated during passive viewing (yellow voxels) and when the participants performed 1-back task (red voxels) shown on the PALS flattened representations of left and right hemispheres (posterior part). The yellow dotted outlines indicate voxels significant at P < 0.001 uncorrected from the passive-viewing experiment. These yellow outlines and voxels are contained in the “active” red voxels. The significant local maxima defined from the active runs are indicated by green dots: (1) and (2) L and R caudal ITG, (3) and (4) L and R mid-FG (middle fusiform gyrus), (5) and (6) L and R mid CollS (collateral sulcus), (7) R mid LG (lingual gyrus), (8.1, 8.2) and (9) L and R LOS, (10) L VIPS, (11) L DIPSM, (12) L DIPSA (Table S3). For other conventions see Figure 6. (B and C) Activity profiles of all local maxima in the passive (fixation) and active (1-back task) runs. Black stars indicate the areas significant in passive conjunction analysis (see Materials and Methods). Yellow stars indicate areas significant in the interaction: (uniform luminance − fixation) task − (uniform luminance − fixation) passive. Inset: examples of the visual stimuli used in the experiment.
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fig15: 3D SfS sensitive regions (control experiment 2, fixed effect, n = 6). (A) Shading specific areas significantly (P < 0.05 corrected) activated during passive viewing (yellow voxels) and when the participants performed 1-back task (red voxels) shown on the PALS flattened representations of left and right hemispheres (posterior part). The yellow dotted outlines indicate voxels significant at P < 0.001 uncorrected from the passive-viewing experiment. These yellow outlines and voxels are contained in the “active” red voxels. The significant local maxima defined from the active runs are indicated by green dots: (1) and (2) L and R caudal ITG, (3) and (4) L and R mid-FG (middle fusiform gyrus), (5) and (6) L and R mid CollS (collateral sulcus), (7) R mid LG (lingual gyrus), (8.1, 8.2) and (9) L and R LOS, (10) L VIPS, (11) L DIPSM, (12) L DIPSA (Table S3). For other conventions see Figure 6. (B and C) Activity profiles of all local maxima in the passive (fixation) and active (1-back task) runs. Black stars indicate the areas significant in passive conjunction analysis (see Materials and Methods). Yellow stars indicate areas significant in the interaction: (uniform luminance − fixation) task − (uniform luminance − fixation) passive. Inset: examples of the visual stimuli used in the experiment.

Mentions: This task was designed to control for variations in attention among the different conditions that could conceivably have played a role in the results of the main study. In order to compel their attention, observers were required to judge whether each successive pair of images was the same or different. To prevent these judgments from being based on the 2D bounding contours of the objects, the stimuli from the main experiment in the 3D shaded, shaded-blob, unshaded-blob, uniform-luminance, 3D lattice, uniform-texture, and lattice-aligned conditions were modified so that they all had identical 6.5° circular boundaries (see Figs 14 and 15, insets). All 11 images of a condition were first resized to subtend approximately 10° of visual angle. Then four 6.5° circular cutouts within the boundary of each object were created that were positioned 0.5° from the center along each diagonal. Thus, with 4 distinct circular patches for each of the original images, there were 44 stimuli per condition. The aim of increasing the stimulus set size was to increase the difficulty of the task and to avoid rote learning. In the uniform-texture condition task difficulty was increased by rotating the images either 20° or −20° in the image plane. The uniform-luminance condition was used in both shading and texture versions of this control experiment as a low-level condition, as well as a fixation-only condition as a baseline. The uniform-luminance condition consisted of 22 different gray-level stimuli with a luminance range from 0 (black) to 255 (white) and an average luminance equal to that of the 3D shaded condition (175 cd/m2). The complete set of stimuli was divided over 2 runs to achieve equal probability (50%) of same and different stimulus sequences. Two or more consecutive repetitions occurred in each epoch. Nevertheless the observers never saw the same stimuli (except in the uniform-luminance condition) in these runs.


The extraction of 3D shape from texture and shading in the human brain.

Georgieva SS, Todd JT, Peeters R, Orban GA - Cereb. Cortex (2008)

3D SfS sensitive regions (control experiment 2, fixed effect, n = 6). (A) Shading specific areas significantly (P < 0.05 corrected) activated during passive viewing (yellow voxels) and when the participants performed 1-back task (red voxels) shown on the PALS flattened representations of left and right hemispheres (posterior part). The yellow dotted outlines indicate voxels significant at P < 0.001 uncorrected from the passive-viewing experiment. These yellow outlines and voxels are contained in the “active” red voxels. The significant local maxima defined from the active runs are indicated by green dots: (1) and (2) L and R caudal ITG, (3) and (4) L and R mid-FG (middle fusiform gyrus), (5) and (6) L and R mid CollS (collateral sulcus), (7) R mid LG (lingual gyrus), (8.1, 8.2) and (9) L and R LOS, (10) L VIPS, (11) L DIPSM, (12) L DIPSA (Table S3). For other conventions see Figure 6. (B and C) Activity profiles of all local maxima in the passive (fixation) and active (1-back task) runs. Black stars indicate the areas significant in passive conjunction analysis (see Materials and Methods). Yellow stars indicate areas significant in the interaction: (uniform luminance − fixation) task − (uniform luminance − fixation) passive. Inset: examples of the visual stimuli used in the experiment.
© Copyright Policy - open-access
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fig15: 3D SfS sensitive regions (control experiment 2, fixed effect, n = 6). (A) Shading specific areas significantly (P < 0.05 corrected) activated during passive viewing (yellow voxels) and when the participants performed 1-back task (red voxels) shown on the PALS flattened representations of left and right hemispheres (posterior part). The yellow dotted outlines indicate voxels significant at P < 0.001 uncorrected from the passive-viewing experiment. These yellow outlines and voxels are contained in the “active” red voxels. The significant local maxima defined from the active runs are indicated by green dots: (1) and (2) L and R caudal ITG, (3) and (4) L and R mid-FG (middle fusiform gyrus), (5) and (6) L and R mid CollS (collateral sulcus), (7) R mid LG (lingual gyrus), (8.1, 8.2) and (9) L and R LOS, (10) L VIPS, (11) L DIPSM, (12) L DIPSA (Table S3). For other conventions see Figure 6. (B and C) Activity profiles of all local maxima in the passive (fixation) and active (1-back task) runs. Black stars indicate the areas significant in passive conjunction analysis (see Materials and Methods). Yellow stars indicate areas significant in the interaction: (uniform luminance − fixation) task − (uniform luminance − fixation) passive. Inset: examples of the visual stimuli used in the experiment.
Mentions: This task was designed to control for variations in attention among the different conditions that could conceivably have played a role in the results of the main study. In order to compel their attention, observers were required to judge whether each successive pair of images was the same or different. To prevent these judgments from being based on the 2D bounding contours of the objects, the stimuli from the main experiment in the 3D shaded, shaded-blob, unshaded-blob, uniform-luminance, 3D lattice, uniform-texture, and lattice-aligned conditions were modified so that they all had identical 6.5° circular boundaries (see Figs 14 and 15, insets). All 11 images of a condition were first resized to subtend approximately 10° of visual angle. Then four 6.5° circular cutouts within the boundary of each object were created that were positioned 0.5° from the center along each diagonal. Thus, with 4 distinct circular patches for each of the original images, there were 44 stimuli per condition. The aim of increasing the stimulus set size was to increase the difficulty of the task and to avoid rote learning. In the uniform-texture condition task difficulty was increased by rotating the images either 20° or −20° in the image plane. The uniform-luminance condition was used in both shading and texture versions of this control experiment as a low-level condition, as well as a fixation-only condition as a baseline. The uniform-luminance condition consisted of 22 different gray-level stimuli with a luminance range from 0 (black) to 255 (white) and an average luminance equal to that of the 3D shaded condition (175 cd/m2). The complete set of stimuli was divided over 2 runs to achieve equal probability (50%) of same and different stimulus sequences. Two or more consecutive repetitions occurred in each epoch. Nevertheless the observers never saw the same stimuli (except in the uniform-luminance condition) in these runs.

Bottom Line: The results of both passive and active experiments reveal that the extraction of 3D SfT involves the bilateral caudal inferior temporal gyrus (caudal ITG), lateral occipital sulcus (LOS) and several bilateral sites along the intraparietal sulcus.Additional results from psychophysical experiments reveal that this difference in neuronal substrate cannot be explained by a difference in strength between the 2 cues.These results underscore the importance of the posterior part of the lateral occipital complex for the extraction of visual 3D shape information from all depth cues, and they suggest strongly that the importance of shading is diminished relative to other cues for the analysis of 3D shape in parietal regions.

View Article: PubMed Central - PubMed

Affiliation: Laboratorium voor Neuro- en Psychofysiologie, Katholieke Universiteit Leuven School of Medicine, Campus Gasthuisberg, B-3000 Leuven, Belgium.

ABSTRACT
We used functional magnetic resonance imaging to investigate the human cortical areas involved in processing 3-dimensional (3D) shape from texture (SfT) and shading. The stimuli included monocular images of randomly shaped 3D surfaces and a wide variety of 2-dimensional (2D) controls. The results of both passive and active experiments reveal that the extraction of 3D SfT involves the bilateral caudal inferior temporal gyrus (caudal ITG), lateral occipital sulcus (LOS) and several bilateral sites along the intraparietal sulcus. These areas are largely consistent with those involved in the processing of 3D shape from motion and stereo. The experiments also demonstrate, however, that the analysis of 3D shape from shading is primarily restricted to the caudal ITG areas. Additional results from psychophysical experiments reveal that this difference in neuronal substrate cannot be explained by a difference in strength between the 2 cues. These results underscore the importance of the posterior part of the lateral occipital complex for the extraction of visual 3D shape information from all depth cues, and they suggest strongly that the importance of shading is diminished relative to other cues for the analysis of 3D shape in parietal regions.

Show MeSH
Related in: MedlinePlus