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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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Results of psychophysical experiments 4 and 5. (A) Slope of line relating texture settings and shading settings in the 3D shape adjustment task plotted as a function of depth magnitude (in % of original). Individual values (black) and medians (red) are plotted. (B and C) Mean and SE of d′ and reaction time in the same-different task plotted as a function of the amplitude of the shape perturbation. In (A) the median correlations were 0.28, 0.95, and 0.98, respectively.
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fig13: Results of psychophysical experiments 4 and 5. (A) Slope of line relating texture settings and shading settings in the 3D shape adjustment task plotted as a function of depth magnitude (in % of original). Individual values (black) and medians (red) are plotted. (B and C) Mean and SE of d′ and reaction time in the same-different task plotted as a function of the amplitude of the shape perturbation. In (A) the median correlations were 0.28, 0.95, and 0.98, respectively.

Mentions: Yet when examining the stimuli in Figure 1, many observers report anecdotally that the shaded objects are perceptually more compelling than those specified by texture. These impressions are borne out by testing the sensitivity for the 2 cues, as suggested by 1 of the anonymous reviewers. A first test was to use the 3D shape adjustment task for stimuli that were flattened compared with the original stimuli of the main experiments. Plotting the texture adjustments as a function of the shading adjustments yielded median slopes over 0.9 for the original stimuli and those flattened to 64% depth (Fig. 13A). However this slope decreased to 0.23 when the depth was further reduced to 28% of the original value. Similar results were obtained with the same-different task probing sensitivity for small perturbations in 3D shape. The sensitivity for 3D shape indexed by the d′ obtained from signal detection analysis was significantly larger for the SfS stimuli than the SfT stimuli (Fig. 13B). A 2-way ANOVA (repeated measures) with perturbation step and cue as factors yielded significant main effects of cue and steps (both P < 10−6) and significant interaction (P < 0.001). The cue also had a small effect on the reaction times, which were marginally longer for the SfT stimuli than the SfS stimuli. Two-way ANOVA revealed a significant main effect of perturbation step (P < 10−6) and a significant interaction (P < 0.0002). These findings are important for interpreting the results of the main experiment because they indicate quite clearly that the reduced pattern of activation for SfS cannot be due to a lower sensitivity for shading information relative to the information provided by texture.


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

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

Results of psychophysical experiments 4 and 5. (A) Slope of line relating texture settings and shading settings in the 3D shape adjustment task plotted as a function of depth magnitude (in % of original). Individual values (black) and medians (red) are plotted. (B and C) Mean and SE of d′ and reaction time in the same-different task plotted as a function of the amplitude of the shape perturbation. In (A) the median correlations were 0.28, 0.95, and 0.98, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2536698&req=5

fig13: Results of psychophysical experiments 4 and 5. (A) Slope of line relating texture settings and shading settings in the 3D shape adjustment task plotted as a function of depth magnitude (in % of original). Individual values (black) and medians (red) are plotted. (B and C) Mean and SE of d′ and reaction time in the same-different task plotted as a function of the amplitude of the shape perturbation. In (A) the median correlations were 0.28, 0.95, and 0.98, respectively.
Mentions: Yet when examining the stimuli in Figure 1, many observers report anecdotally that the shaded objects are perceptually more compelling than those specified by texture. These impressions are borne out by testing the sensitivity for the 2 cues, as suggested by 1 of the anonymous reviewers. A first test was to use the 3D shape adjustment task for stimuli that were flattened compared with the original stimuli of the main experiments. Plotting the texture adjustments as a function of the shading adjustments yielded median slopes over 0.9 for the original stimuli and those flattened to 64% depth (Fig. 13A). However this slope decreased to 0.23 when the depth was further reduced to 28% of the original value. Similar results were obtained with the same-different task probing sensitivity for small perturbations in 3D shape. The sensitivity for 3D shape indexed by the d′ obtained from signal detection analysis was significantly larger for the SfS stimuli than the SfT stimuli (Fig. 13B). A 2-way ANOVA (repeated measures) with perturbation step and cue as factors yielded significant main effects of cue and steps (both P < 10−6) and significant interaction (P < 0.001). The cue also had a small effect on the reaction times, which were marginally longer for the SfT stimuli than the SfS stimuli. Two-way ANOVA revealed a significant main effect of perturbation step (P < 10−6) and a significant interaction (P < 0.0002). These findings are important for interpreting the results of the main experiment because they indicate quite clearly that the reduced pattern of activation for SfS cannot be due to a lower sensitivity for shading information relative to the information provided by texture.

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