Abstract
Visual analysis of real-life scenes starts with the parallel extraction of different visual elementary features at different spatial frequencies. The global shape of the scene is mainly contained in low spatial frequencies (LSF), and the edges and borders of objects are mainly contained in high spatial frequencies (HSF). The present fMRI study investigates the effect of age on the spatial frequency processing in scenes. Young and elderly participants performed a categorization task (indoor vs. outdoor) on LSF and HSF scenes. Behavioral results revealed performance degradation for elderly participants only when categorizing HSF scenes. At the cortical level, young participants exhibited retinotopic organization of spatial frequency processing, characterized by medial activation in the anterior part of the occipital lobe for LSF scenes (compared to HSF), and the lateral activation in the posterior part of the occipital lobe for HSF scenes (compared to LSF). Elderly participants showed activation only in the anterior part of the occipital lobe for LSF scenes (compared to HSF), but not significant activation for HSF (compared to LSF). Furthermore, a ROI analysis revealed that the parahippocampal place area, a scene-selective region, was less activated for HSF than LSF for elderly participants only. Comparison between groups revealed greater activation of the right inferior occipital gyrus in young participants than in elderly participants for HSF. Activation of temporo-parietal regions was greater in elderly participants irrespective of spatial frequencies. The present findings indicate a specific low-contrasted HSF deficit for normal elderly people, in association with an occipito-temporal cortex dysfunction, and a functional reorganization of the categorization of filtered scenes.
Highlights
Three 2x3x2 analyses of variance (ANOVA) with Group as between-subjects factor, and Spatial frequency (NF, low spatial frequencies (LSF), and high spatial frequencies (HSF)) and Category as within-subjects factors were conducted on mean nonresponse error rate (mNR), mean false categorization rate (mFC) and mean correct reaction times (mRT)
Planned comparison showed that elderly participants responded less often when categorizing HSF scenes (49.2 ± 26.9%) than non-filtered scenes (NF) scenes (0.3 ± 0.8%; F1,22 = 80.79, p < 0.001) and LSF scenes (2.8 ± 5.0%; F1,22 = 85.01, p < 0.001), and when categorizing LSF than NF scenes (F1,22 = 7.52, p < 0.05)
The present findings indicate a specific low-contrasted HSF deficit in elderly people, in association with occipito-temporal cortex dysfunction
Summary
Visual scenes of daily life, such as outdoor or indoor environments, contain many visual objects made of smaller objects comprising multiple visual details. There is considerable evidence suggesting that the spatial frequency content of scenes is important for organized perception. Spatial Frequency Processing and Aging analysis, decision to publish, or preparation of the manuscript
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