Limits...
Is coarse-to-fine strategy sensitive to normal aging?

Musel B, Chauvin A, Guyader N, Chokron S, Peyrin C - PLoS ONE (2012)

Bottom Line: 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).The results show that young participants categorized CtF sequences more quickly than FtC sequences.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Psychologie et NeuroCognition, CNRS - UMR 5105, Université Pierre Mendès France, Grenoble, France. benoit.musel@upmf-grenoble.fr

ABSTRACT
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.

Show MeSH
Example of six spatial frequency filtered images of scenes belonging to different categories (indoors and outdoors) that depict the coarse-to-fine and fine-to-coarse movies.Mean amplitude spectra of each categories. On each amplitude spectrum, the low spatial frequencies are close to the center, while the high spatial frequencies are in the periphery. The vertical orientations are represented on the x-axis while the horizontal orientations are represented on the y-axis.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3366939&req=5

pone-0038493-g001: Example of six spatial frequency filtered images of scenes belonging to different categories (indoors and outdoors) that depict the coarse-to-fine and fine-to-coarse movies.Mean amplitude spectra of each categories. On each amplitude spectrum, the low spatial frequencies are close to the center, while the high spatial frequencies are in the periphery. The vertical orientations are represented on the x-axis while the horizontal orientations are represented on the y-axis.

Mentions: Stimuli consisted of 40 black and white photographs (256-level grey-scales) of natural scenes classified into two distinct categories (20 indoor scenes and 20 outdoor scenes) with a visual angle of 24×18 degrees. Exemplar from the two categories (outdoor and indoor) were chosen in order to have similar amplitude spectrum to avoid their identification on the basis of this type of visual cue [21], but also to avoid contrast energy differences between categories that could interfere with the sequence of spatial frequency processing. In both categories, images have the same distribution of energy in spatial frequencies and dominant orientations (as shown by the mean amplitude spectrum of non-filtered natural scenes in each category; Figure 1). Stimuli were elaborated using the image processing toolbox on MATLAB (Mathworks Inc., Sherborn, MA, USA). We presented brief movies containing a succession of spatial frequency filtered scenes, going either from lower to higher frequency or vice versa. This allowed us to experimentally “decompose” the visual inputs in either CtF or FtC sequences. For each scene, we created two movies: one following a CtF sequence (see Video S1 and S3) and one following a FtC sequence (see Video S2 and S4). Each movie lasted 150 ms and was composed of the same scene filtered in 6 different frequency bands (presented 25 ms). Scenes were filtered using Gaussian band pass filters with different central frequencies equivalent to a visual angle of to 1, 2, 3, 4, 5, 6 cycles/degree, and a standard deviation of 1.67 cycles/degree (or 24, 48, 72, 96, 120, 144 cycles/image and a standard deviation of 40 cycles/image). The cut off frequencies at 67% of the height of each Gaussian were, therefore, [0 2.7]; [0.3 3.7]; [1.3 4.7]; [2.3 5.7]; [3.3 6.7]; [4.3 7.7] cycles/degree; (i.e. [0 64]; [8 88]; [32 112]; [56 136]; [80 160]; [104 184] cycles/image). Stimuli were displayed using E-prime software (E-prime Psychology Software Tools Inc., Pittsburgh, USA) on a computer monitor (17-inch, with a resolution of 1024×768 pixel size, 75 Hz) at a viewing distance of 73 cm. In order to respect the distance and the central position, participants' heads were supported by a chin rest.


Is coarse-to-fine strategy sensitive to normal aging?

Musel B, Chauvin A, Guyader N, Chokron S, Peyrin C - PLoS ONE (2012)

Example of six spatial frequency filtered images of scenes belonging to different categories (indoors and outdoors) that depict the coarse-to-fine and fine-to-coarse movies.Mean amplitude spectra of each categories. On each amplitude spectrum, the low spatial frequencies are close to the center, while the high spatial frequencies are in the periphery. The vertical orientations are represented on the x-axis while the horizontal orientations are represented on the y-axis.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3366939&req=5

pone-0038493-g001: Example of six spatial frequency filtered images of scenes belonging to different categories (indoors and outdoors) that depict the coarse-to-fine and fine-to-coarse movies.Mean amplitude spectra of each categories. On each amplitude spectrum, the low spatial frequencies are close to the center, while the high spatial frequencies are in the periphery. The vertical orientations are represented on the x-axis while the horizontal orientations are represented on the y-axis.
Mentions: Stimuli consisted of 40 black and white photographs (256-level grey-scales) of natural scenes classified into two distinct categories (20 indoor scenes and 20 outdoor scenes) with a visual angle of 24×18 degrees. Exemplar from the two categories (outdoor and indoor) were chosen in order to have similar amplitude spectrum to avoid their identification on the basis of this type of visual cue [21], but also to avoid contrast energy differences between categories that could interfere with the sequence of spatial frequency processing. In both categories, images have the same distribution of energy in spatial frequencies and dominant orientations (as shown by the mean amplitude spectrum of non-filtered natural scenes in each category; Figure 1). Stimuli were elaborated using the image processing toolbox on MATLAB (Mathworks Inc., Sherborn, MA, USA). We presented brief movies containing a succession of spatial frequency filtered scenes, going either from lower to higher frequency or vice versa. This allowed us to experimentally “decompose” the visual inputs in either CtF or FtC sequences. For each scene, we created two movies: one following a CtF sequence (see Video S1 and S3) and one following a FtC sequence (see Video S2 and S4). Each movie lasted 150 ms and was composed of the same scene filtered in 6 different frequency bands (presented 25 ms). Scenes were filtered using Gaussian band pass filters with different central frequencies equivalent to a visual angle of to 1, 2, 3, 4, 5, 6 cycles/degree, and a standard deviation of 1.67 cycles/degree (or 24, 48, 72, 96, 120, 144 cycles/image and a standard deviation of 40 cycles/image). The cut off frequencies at 67% of the height of each Gaussian were, therefore, [0 2.7]; [0.3 3.7]; [1.3 4.7]; [2.3 5.7]; [3.3 6.7]; [4.3 7.7] cycles/degree; (i.e. [0 64]; [8 88]; [32 112]; [56 136]; [80 160]; [104 184] cycles/image). Stimuli were displayed using E-prime software (E-prime Psychology Software Tools Inc., Pittsburgh, USA) on a computer monitor (17-inch, with a resolution of 1024×768 pixel size, 75 Hz) at a viewing distance of 73 cm. In order to respect the distance and the central position, participants' heads were supported by a chin rest.

Bottom Line: 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).The results show that young participants categorized CtF sequences more quickly than FtC sequences.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Psychologie et NeuroCognition, CNRS - UMR 5105, Université Pierre Mendès France, Grenoble, France. benoit.musel@upmf-grenoble.fr

ABSTRACT
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.

Show MeSH