Age-related differences in spatial frequency processing during scene categorization

International audienceIntroduction:Real-life visual scenes are primarily processed in terms of spatial frequencies. Low spatial frequencies (LSF) convey the global shape of the scene, and high spatial frequencies (HSF) convey the edges and borders of objects. Recent neuroimaging studies have aimed to identify the cerebral regions differentially involved in LSF and HSF processing in young adults (for a recent review, Kauffman, Ramanoël, & Peyrin, 2014). However, theway spatial frequencies are processed in normal aging remains unclear. The present fMRI study investigates how the spatial frequency processing of scenes evolves with aging.Methods:Twelve young (22±3 years) and 12 elderly (64±3 years) right-handed participants performed a categorization task using large black and white photographs of scenes (indoors vs. outdoors, with a visual angle of 24°×18°) filtered in LSF (cutoff frequencies: 0.5, 1, 2 cpd), HSF (cutoff frequencies: 3, 6, 12 cpd), and non-filtered scenes, in a block-designed fMRI experiment consisting of four functional runs. Each functional scan was composed of nine 25-sec task blocks (one block per spatial frequency cut-off and three blocks of NF scenes), including 10 scenes (5 indoors and 5 outdoors), interspersed with three 25-sec blocks with a fixation dot in the center of the screen displayed against a grey background. Each scene was displayed for 100 ms, followed by a mask for 30 ms (1/f white noise) to prevent retinal persistence. Experiment was performed using a whole-body 3T Philips scanner (Achieva 3.0T TX Philips) with a 32-channel head coil at the University Hospital Center of Grenoble in France. Data analysis was performed using the general linear model for block designs in SPM12b (Wellcome Department of Imaging Neuroscience, London, UK). On an individual level, we first identified the brain regions involved in the processing of each spatial frequency content relative to the fixation ([LSF>fixation], [HSF>fixation], [NF>fixation]). To allow population inference, ANOVAs were performed based on individual analysis by means of a flexible-factorial design. Areas of activation were considered significant if they exceeded a voxel threshold of p