Alan Chauvin - Academia.edu (original) (raw)

Papers by Alan Chauvin

Journal of Vision, 2010

We used the Bubbles method (Gosselin & Schyns, 2001) to examine the effective use of spatial ... more We used the Bubbles method (Gosselin & Schyns, 2001) to examine the effective use of spatial frequencies through time in natural scene categorization. Two observers (CE and KT) categorized a total of 8640 dynamic stimuli (6 deg 2 of visual angle*180ms) composed of one of 720 ...

Journal of Vision, 2011

Abstract Complex natural scenes are very quickly categorized, faster than 150 ms, suggesting a si... more Abstract Complex natural scenes are very quickly categorized, faster than 150 ms, suggesting a simple and efficient processing. Recent models of visual recognition have suggested that perceptual analysis may start with a parallel extraction of different spatial ...

PLoS ONE, 2012

Theories on visual perception agree that visual recognition begins with global analysis and ends ... more Theories on visual perception agree that visual recognition begins with global analysis and ends with detailed analysis. Different results from neurophysiological, computational, and behavioral studies all indicate that the totality of visual information is not immediately conveyed, but that information analysis follows a predominantly coarse-to-fine processing sequence (low spatial frequencies are extracted first, followed by high spatial frequencies). We tested whether such processing continues to occur in normally aging subjects. Young and aged participants performed a categorization task (indoor vs. outdoor scenes), using dynamic natural scene stimuli, in which they resorted to either a coarse-to-fine (CtF) sequence or a reverse fine-to-coarse sequence (FtC). The results show that young participants categorized CtF sequences more quickly than FtC sequences. However, sequence processing interacts with semantic category only for aged participants. The present data support the notion that CtF categorization is effective even in aged participants, but is constrained by the spatial features of the scenes, thus highlighting new perspectives in visual models.

Journal of Cognitive Neuroscience, 2014

■ Neurophysiological, behavioral, and computational data indicate that visual analysis may start ... more ■ Neurophysiological, behavioral, and computational data indicate that visual analysis may start with the parallel extraction of different elementary attributes at different spatial frequencies and follows a predominantly coarse-to-fine (CtF) processing sequence (low spatial frequencies [LSF] are extracted first, followed by high spatial frequencies [HSF]). Evidence for CtF processing within scene-selective cortical regions is however still lacking. In the present fMRI study, we tested whether such processing occurs in three scene-selective cortical regions: the parahippocampal place area (PPA), the retrosplenial cortex, and the occipital place area. Fourteen participants were subjected to functional scans during which they performed a categorization task of indoor versus outdoor scenes using dynamic scene stimuli. Dynamic scenes were composed of six filtered images of the same scene, from LSF to HSF or from HSF to LSF, allowing us to mimic a CtF or the reverse fine-to-coarse (FtC) sequence. Results showed that only the PPA was more activated for CtF than FtC sequences. Equivalent activations were observed for both sequences in the retrosplenial cortex and occipital place area. This study suggests for the first time that CtF sequence processing constitutes the predominant strategy for scene categorization in the PPA. ■

Journal of Experimental Psychology-human Perception and Performance, 2010

The authors examined spatial frequency (SF) tuning of upright and inverted face identification us... more The authors examined spatial frequency (SF) tuning of upright and inverted face identification using an SF variant of the Bubbles technique (F. . In Experiment 1, they validated the SF Bubbles technique in a plaid detection task. In Experiments 2a-c, the SFs used for identifying upright and inverted inner facial features were investigated. Although a clear inversion effect was present (mean accuracy was 24% higher and response times 455 ms shorter for upright faces), SF tunings were remarkably similar in both orientation conditions (mean r ϭ .98; an SF band of 1.9 octaves centered at 9.8 cycles per face width for faces of about 6°). In Experiments 3a and b, the authors demonstrated that their technique is sensitive to both subtle bottom-up and top-down induced changes in SF tuning, suggesting that the null results of Experiments 2a-c are real. The most parsimonious explanation of the findings is provided by the quantitative account of the face inversion effect: The same information is used for identifying upright and inverted inner facial features, but processing has greater sensitivity with the former.

Cognitive Neuroscience, 2012

Instructing participants to “identify a target” dramatically reduces saccadic reaction times in p... more Instructing participants to “identify a target” dramatically reduces saccadic reaction times in prosaccade tasks (PS). However, it has been recently shown that this effect disappears in antisaccade tasks (AS). The instruction effect observed in PS may result from top-down processes, mediated by pathways connecting the prefrontal cortex (PFC) to the superior colliculus. In AS, the PFC's prior involvement is in competition with the instruction process, annulling its effect. This study aims to discover whether the instruction effect persists in mixed paradigms. According to Dyckman's fMRI study (2007), the difficulty of mixed tasks leads to PFC involvement. The antisaccade-related PFC activation observed on comparison of blocked AS and PS therefore disappears when the two are compared in mixed paradigms. However, we continued to observe the instruction effect for both PS and AS. We therefore posit different types of PFC activation: phasic during blocked AS, and tonic during mixed saccadic experiments.

Brain and Cognition, 2005

The human perceptual system seems to be driven by a coarse-to-fine integration of visual informat... more The human perceptual system seems to be driven by a coarse-to-fine integration of visual information. Different results have shown a faster integration of low-spatial frequency compared with high-spatial frequency (HSF) information, starting at early retinal processes. The difference in spatial scale decomposition remains throughout the lateral geniculate nucleus (Hubel & Wiesel, 1977) and V1 (Tootell, Silverman, & De Valois, 1981). During the last decade, a debate has emerged concerning the origin of the coarse-to-fine integration. Is it a constant, perceptually driven integration (21 and 22)? Instead, the flexible use hypothesis suggests that different spatial frequency channels could be enhanced depending on the requirement of the task for high-level cognitive processes like categorization (19 and 25). In two connectionist simulations, we have shown that global categorization performance could actually be better performed with HSF information when the amount of information is normalized across the different spatial frequency channels. Those results suggest that high-level requirement alone could not explain the coarse-to-fine bias toward LSF information. A hypothesis is proposed concerning the possible implication of the amount of data provided by different spatial frequency channel that might provide the perceptual bias toward LSF information.

La recherche d'un segment de ligne 'cible' différant des segments de lignes 'distracteurs' par un... more La recherche d'un segment de ligne 'cible' différant des segments de lignes 'distracteurs' par une orientation d'une vingtaine de degrés se marque d'une curieuse anisotropie : la recherche est plus facile (rapide) si la cible est oblique que si elle est verticale (ou horizontale). Dans des travaux récents, nous avons montré que l'anisotropie variait en fonction de la posture des sujets, signifiant que la recherche visuelle d'orientation, habituellement décrite et modélisée sous forme de traitements visuels de bas niveau , se fait cependant après une étape d'intégration intersensorielle ). Est-elle sensible aux informations mnésiques ? Pour répondre à cette question, nous avons substitué aux segments de ligne des formes représentant des animaux dont l'orientation canonique est soit verticale soit oblique. Les résultats montrent que c'est l'orientation canonique, et non l'orientation physique, qui détermine l'anisotropie. La recherche visuelle d'orientations est donc sensible aux informations mnésiques, lesquelles l'emportent sur le signal en cas de conflit alors qu'elles ne sont a priori d'aucune utilité pour résoudre la tâche. Ce que confirment deux contre-expériences, l'une réalisée chez le sujet cérébro-lésé (agnosie visuelle), l'autre manipulant le contenu fréquentiel des images.

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Brain and Cognition, 2005

Brain and Cognition, 2004

At the earliest ages of development, perceptual maturation is generally considered as a functiona... more At the earliest ages of development, perceptual maturation is generally considered as a functional constraint to recognize or categorize the stimuli of the environment. However, using a computer simulation of retinal development using Gabor wavelets to simulate the output of the V1 complex cells , we showed that reducing the range of the spatial frequencies from the retinal map to V1 decreases the variance distribution within a category. The consequence of this is to decrease the difference between two exemplars of the same category, but to increase the difference between exemplars from two different categories. These results show that reduced perceptual acuity produces an advantage for differentiating basic-level categories. Finally, we show that the present simulations using Gabor-filtered input instead of feature-based input coding provide a pattern of statistical data convergent with previously published results in infant categorization (e.g.,

Brain and Cognition, 2005

The distribution of striate cortex cells exhibits a maximum number of cells tuned to vertical and... more The distribution of striate cortex cells exhibits a maximum number of cells tuned to vertical and horizontal orientations (Mansfield, 1974). This was interpreted as an adaptation of the visual system to the presence in the visual environment of greater amounts of vertical and horizontal information compared to information from other orientations (Keil & Cristobal, 2000). The present research confirms that vertical and horizontal orientations are, indeed, present in greater number in natural scenes. After normalization of the amount of information across all orientations, vertical information appeared to be better for bottom–up categorization. We demonstrate this using a connectionist autoassociator model of categorization used elsewhere in simulations of early infant categorization.

Comptes Rendus Biologies, 2004

Models of the visual cortex are based on image decomposition according to the Fourier spectrum (a... more Models of the visual cortex are based on image decomposition according to the Fourier spectrum (amplitude and phase). On one hand, it is commonly believed that phase information is necessary to identify a scene. On the other hand, it is known that complex cells of the visual cortex, the most numerous ones, code only the amplitude spectrum. This raises the question of knowing if these cells carry sufficient information to allow visual scene categorization. In this work, using the same experiments in computer simulation and in psychophysics, we provide arguments to show that the amplitude spectrum alone is sufficient for categorization task. To cite this article: N. Guyader et al., C. R. Biologies 327 (2004).En traitement d'image, la modélisation du cortex visuel permet une décomposition des images selon leur spectre de Fourier (amplitude et phase). Il est communément admis que l'information de phase est nécessaire à l'identification d'une scène. Or, nous savons que les cellules complexes du cortex visuel (les plus nombreuses) codent uniquement le spectre d'amplitude. Se pose alors la question de savoir si ces cellules véhiculent une information suffisante pour permettre la catégorisation de scènes visuelles. Nous montrons, par une simulation informatique inspirée de la biologie du système visuel et par une expérience de psychophysique, que le spectre d'amplitude seul suffit à catégoriser des scènes. Pour citer cet article : N. Guyader et al., C. R. Biologies 327 (2004).

Brain and Cognition, 2003

Experimental data coming from visual cognitive sciences suggest that visual analysis starts with ... more Experimental data coming from visual cognitive sciences suggest that visual analysis starts with a parallel extraction of different visual attributes at different scales/frequencies. Neuropsychological and functional imagery data have suggested that each hemisphere (at the level of temporo-parietal junctions-TPJ) could play a key role in spatial frequency processing: The right TPJ should predominantly be involved in low spatial frequency (LFs) analysis and the left TPJ in high spatial frequency (HFs) analysis. Nevertheless, this functional hypothesis had been inferred from data obtained when using the hierarchical form paradigm, without any explicit spatial frequency manipulation per se. The aims of this research are (i) to investigate, in healthy subjects, the hemispheric asymmetry hypothesis with an explicit manipulation of spatial frequencies of natural scenes and (ii) to examine whether the Ôprecedence effectÕ (the relative rapidity of LFs and HFs processing) depends on the visual field of scene presentation or not. For this purpose, participants were to identify either non-filtered or LFs and HFs filtered target scene displayed either in the left, central, or right visual field. Results showed a hemispheric specialization for spatial frequency processing and different Ôprecedence effectsÕ depending on the visual field of presentation.

Journal of Vision, 2010

We used the Bubbles method (Gosselin & Schyns, 2001) to examine the effective use of spatial ... more We used the Bubbles method (Gosselin & Schyns, 2001) to examine the effective use of spatial frequencies through time in natural scene categorization. Two observers (CE and KT) categorized a total of 8640 dynamic stimuli (6 deg 2 of visual angle*180ms) composed of one of 720 ...

Journal of Vision, 2011

Abstract Complex natural scenes are very quickly categorized, faster than 150 ms, suggesting a si... more Abstract Complex natural scenes are very quickly categorized, faster than 150 ms, suggesting a simple and efficient processing. Recent models of visual recognition have suggested that perceptual analysis may start with a parallel extraction of different spatial ...

PLoS ONE, 2012

Theories on visual perception agree that visual recognition begins with global analysis and ends ... more Theories on visual perception agree that visual recognition begins with global analysis and ends with detailed analysis. Different results from neurophysiological, computational, and behavioral studies all indicate that the totality of visual information is not immediately conveyed, but that information analysis follows a predominantly coarse-to-fine processing sequence (low spatial frequencies are extracted first, followed by high spatial frequencies). We tested whether such processing continues to occur in normally aging subjects. Young and aged participants performed a categorization task (indoor vs. outdoor scenes), using dynamic natural scene stimuli, in which they resorted to either a coarse-to-fine (CtF) sequence or a reverse fine-to-coarse sequence (FtC). The results show that young participants categorized CtF sequences more quickly than FtC sequences. However, sequence processing interacts with semantic category only for aged participants. The present data support the notion that CtF categorization is effective even in aged participants, but is constrained by the spatial features of the scenes, thus highlighting new perspectives in visual models.

Journal of Cognitive Neuroscience, 2014

■ Neurophysiological, behavioral, and computational data indicate that visual analysis may start ... more ■ Neurophysiological, behavioral, and computational data indicate that visual analysis may start with the parallel extraction of different elementary attributes at different spatial frequencies and follows a predominantly coarse-to-fine (CtF) processing sequence (low spatial frequencies [LSF] are extracted first, followed by high spatial frequencies [HSF]). Evidence for CtF processing within scene-selective cortical regions is however still lacking. In the present fMRI study, we tested whether such processing occurs in three scene-selective cortical regions: the parahippocampal place area (PPA), the retrosplenial cortex, and the occipital place area. Fourteen participants were subjected to functional scans during which they performed a categorization task of indoor versus outdoor scenes using dynamic scene stimuli. Dynamic scenes were composed of six filtered images of the same scene, from LSF to HSF or from HSF to LSF, allowing us to mimic a CtF or the reverse fine-to-coarse (FtC) sequence. Results showed that only the PPA was more activated for CtF than FtC sequences. Equivalent activations were observed for both sequences in the retrosplenial cortex and occipital place area. This study suggests for the first time that CtF sequence processing constitutes the predominant strategy for scene categorization in the PPA. ■

Journal of Experimental Psychology-human Perception and Performance, 2010

The authors examined spatial frequency (SF) tuning of upright and inverted face identification us... more The authors examined spatial frequency (SF) tuning of upright and inverted face identification using an SF variant of the Bubbles technique (F. . In Experiment 1, they validated the SF Bubbles technique in a plaid detection task. In Experiments 2a-c, the SFs used for identifying upright and inverted inner facial features were investigated. Although a clear inversion effect was present (mean accuracy was 24% higher and response times 455 ms shorter for upright faces), SF tunings were remarkably similar in both orientation conditions (mean r ϭ .98; an SF band of 1.9 octaves centered at 9.8 cycles per face width for faces of about 6°). In Experiments 3a and b, the authors demonstrated that their technique is sensitive to both subtle bottom-up and top-down induced changes in SF tuning, suggesting that the null results of Experiments 2a-c are real. The most parsimonious explanation of the findings is provided by the quantitative account of the face inversion effect: The same information is used for identifying upright and inverted inner facial features, but processing has greater sensitivity with the former.

Cognitive Neuroscience, 2012

Instructing participants to “identify a target” dramatically reduces saccadic reaction times in p... more Instructing participants to “identify a target” dramatically reduces saccadic reaction times in prosaccade tasks (PS). However, it has been recently shown that this effect disappears in antisaccade tasks (AS). The instruction effect observed in PS may result from top-down processes, mediated by pathways connecting the prefrontal cortex (PFC) to the superior colliculus. In AS, the PFC's prior involvement is in competition with the instruction process, annulling its effect. This study aims to discover whether the instruction effect persists in mixed paradigms. According to Dyckman's fMRI study (2007), the difficulty of mixed tasks leads to PFC involvement. The antisaccade-related PFC activation observed on comparison of blocked AS and PS therefore disappears when the two are compared in mixed paradigms. However, we continued to observe the instruction effect for both PS and AS. We therefore posit different types of PFC activation: phasic during blocked AS, and tonic during mixed saccadic experiments.

Brain and Cognition, 2005

The human perceptual system seems to be driven by a coarse-to-fine integration of visual informat... more The human perceptual system seems to be driven by a coarse-to-fine integration of visual information. Different results have shown a faster integration of low-spatial frequency compared with high-spatial frequency (HSF) information, starting at early retinal processes. The difference in spatial scale decomposition remains throughout the lateral geniculate nucleus (Hubel & Wiesel, 1977) and V1 (Tootell, Silverman, & De Valois, 1981). During the last decade, a debate has emerged concerning the origin of the coarse-to-fine integration. Is it a constant, perceptually driven integration (21 and 22)? Instead, the flexible use hypothesis suggests that different spatial frequency channels could be enhanced depending on the requirement of the task for high-level cognitive processes like categorization (19 and 25). In two connectionist simulations, we have shown that global categorization performance could actually be better performed with HSF information when the amount of information is normalized across the different spatial frequency channels. Those results suggest that high-level requirement alone could not explain the coarse-to-fine bias toward LSF information. A hypothesis is proposed concerning the possible implication of the amount of data provided by different spatial frequency channel that might provide the perceptual bias toward LSF information.

La recherche d'un segment de ligne 'cible' différant des segments de lignes 'distracteurs' par un... more La recherche d'un segment de ligne 'cible' différant des segments de lignes 'distracteurs' par une orientation d'une vingtaine de degrés se marque d'une curieuse anisotropie : la recherche est plus facile (rapide) si la cible est oblique que si elle est verticale (ou horizontale). Dans des travaux récents, nous avons montré que l'anisotropie variait en fonction de la posture des sujets, signifiant que la recherche visuelle d'orientation, habituellement décrite et modélisée sous forme de traitements visuels de bas niveau , se fait cependant après une étape d'intégration intersensorielle ). Est-elle sensible aux informations mnésiques ? Pour répondre à cette question, nous avons substitué aux segments de ligne des formes représentant des animaux dont l'orientation canonique est soit verticale soit oblique. Les résultats montrent que c'est l'orientation canonique, et non l'orientation physique, qui détermine l'anisotropie. La recherche visuelle d'orientations est donc sensible aux informations mnésiques, lesquelles l'emportent sur le signal en cas de conflit alors qu'elles ne sont a priori d'aucune utilité pour résoudre la tâche. Ce que confirment deux contre-expériences, l'une réalisée chez le sujet cérébro-lésé (agnosie visuelle), l'autre manipulant le contenu fréquentiel des images.

[

Brain and Cognition, 2005

Brain and Cognition, 2004

At the earliest ages of development, perceptual maturation is generally considered as a functiona... more At the earliest ages of development, perceptual maturation is generally considered as a functional constraint to recognize or categorize the stimuli of the environment. However, using a computer simulation of retinal development using Gabor wavelets to simulate the output of the V1 complex cells , we showed that reducing the range of the spatial frequencies from the retinal map to V1 decreases the variance distribution within a category. The consequence of this is to decrease the difference between two exemplars of the same category, but to increase the difference between exemplars from two different categories. These results show that reduced perceptual acuity produces an advantage for differentiating basic-level categories. Finally, we show that the present simulations using Gabor-filtered input instead of feature-based input coding provide a pattern of statistical data convergent with previously published results in infant categorization (e.g.,

Brain and Cognition, 2005

The distribution of striate cortex cells exhibits a maximum number of cells tuned to vertical and... more The distribution of striate cortex cells exhibits a maximum number of cells tuned to vertical and horizontal orientations (Mansfield, 1974). This was interpreted as an adaptation of the visual system to the presence in the visual environment of greater amounts of vertical and horizontal information compared to information from other orientations (Keil & Cristobal, 2000). The present research confirms that vertical and horizontal orientations are, indeed, present in greater number in natural scenes. After normalization of the amount of information across all orientations, vertical information appeared to be better for bottom–up categorization. We demonstrate this using a connectionist autoassociator model of categorization used elsewhere in simulations of early infant categorization.

Comptes Rendus Biologies, 2004

Models of the visual cortex are based on image decomposition according to the Fourier spectrum (a... more Models of the visual cortex are based on image decomposition according to the Fourier spectrum (amplitude and phase). On one hand, it is commonly believed that phase information is necessary to identify a scene. On the other hand, it is known that complex cells of the visual cortex, the most numerous ones, code only the amplitude spectrum. This raises the question of knowing if these cells carry sufficient information to allow visual scene categorization. In this work, using the same experiments in computer simulation and in psychophysics, we provide arguments to show that the amplitude spectrum alone is sufficient for categorization task. To cite this article: N. Guyader et al., C. R. Biologies 327 (2004).En traitement d'image, la modélisation du cortex visuel permet une décomposition des images selon leur spectre de Fourier (amplitude et phase). Il est communément admis que l'information de phase est nécessaire à l'identification d'une scène. Or, nous savons que les cellules complexes du cortex visuel (les plus nombreuses) codent uniquement le spectre d'amplitude. Se pose alors la question de savoir si ces cellules véhiculent une information suffisante pour permettre la catégorisation de scènes visuelles. Nous montrons, par une simulation informatique inspirée de la biologie du système visuel et par une expérience de psychophysique, que le spectre d'amplitude seul suffit à catégoriser des scènes. Pour citer cet article : N. Guyader et al., C. R. Biologies 327 (2004).

Brain and Cognition, 2003

Experimental data coming from visual cognitive sciences suggest that visual analysis starts with ... more Experimental data coming from visual cognitive sciences suggest that visual analysis starts with a parallel extraction of different visual attributes at different scales/frequencies. Neuropsychological and functional imagery data have suggested that each hemisphere (at the level of temporo-parietal junctions-TPJ) could play a key role in spatial frequency processing: The right TPJ should predominantly be involved in low spatial frequency (LFs) analysis and the left TPJ in high spatial frequency (HFs) analysis. Nevertheless, this functional hypothesis had been inferred from data obtained when using the hierarchical form paradigm, without any explicit spatial frequency manipulation per se. The aims of this research are (i) to investigate, in healthy subjects, the hemispheric asymmetry hypothesis with an explicit manipulation of spatial frequencies of natural scenes and (ii) to examine whether the Ôprecedence effectÕ (the relative rapidity of LFs and HFs processing) depends on the visual field of scene presentation or not. For this purpose, participants were to identify either non-filtered or LFs and HFs filtered target scene displayed either in the left, central, or right visual field. Results showed a hemispheric specialization for spatial frequency processing and different Ôprecedence effectsÕ depending on the visual field of presentation.