Abstract
Hemispheric specialization for spatial frequency processing was investigated by measuring the contrast sensitivity curves of sine-wave gratings in 30 left or right brain-damaged patients using different spatial frequencies compared with healthy participants. The results showed that left brain-damaged patients were selectively impaired in processing high frequencies, whereas right brain-damaged patients were more impaired in the processing low frequencies, regardless of the presence of visuo-spatial neglect. These visual processing results can be interpreted in terms of spatial frequency discrimination, with both hemispheres participating in this process in different ways.
Highlights
The role of factors related to hemispheric asymmetry in visual information processing has been long considered and debated in studies of perception (Koningsbruggen et al, 2010; Stevens et al, 2012)
The Duncan post-hoc test showed that the LN− (p < 0.001), RN− (p < 0.001), and RN+ (p < 0.002) groups needed more contrast to detect low spatial frequencies compared with the control group (CG)
The data demonstrated larger impairment in detecting high frequencies in patients with lesions in the left hemisphere (LH) (LN− group) and low frequencies in patients with lesions in the right hemisphere (RH) (RN− and RN+ groups). This suggests a double-dissociation between frequency and affected hemisphere
Summary
The role of factors related to hemispheric asymmetry in visual information processing has been long considered and debated in studies of perception (Koningsbruggen et al, 2010; Stevens et al, 2012). With regard to the anatomical and physiological aspects of visual processing, parallel groups of visual pathways consist of parvocellular cells that respond better to medium and high luminance patterns and magnocellular cells that respond better to low luminance patterns. These layers are involved in differences in achromatic contrast sensitivity under scotopic and photopic luminance conditions, respectively. No consensus has been reached about the hemispheres’ roles in medium spatial frequency processing or how visual neglect could be implicated in this processing (Hellige, 1995; Grabowska and Nowicka, 1996; Karnath and Niemerier, 2002)
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