Age effects on saccadic suppression of luminance and color

The execution of saccadic eye movements suppresses visual processing of both color and luminance in the early visual cortex of humans

Our eyes execute rapid, directional movements known as saccades, occurring several times per second, to focus on objects of interest in our environment. During these movements, visual sensitivity is temporarily reduced. Despite numerous studies on this topic, the underlying mechanism remains elusive, including a lingering debate on whether saccadic suppression affects the parvocellular visual pathway. To address this issue, we conducted a study employing steady-state visual evoked potentials (SSVEPs) elicited by chromatic and luminance stimuli while observers performed saccadic eye movements. We also employed an innovative analysis pipeline to enhance the signal-to-noise ratio, yielding superior results compared to the previous method. Our findings revealed a clear suppression effect on SSVEP signals during saccades compared to fixation periods. Notably, this suppression effect was comparable for both chromatic and luminance stimuli. We went further to measure the suppression effect across various contrast levels, which enabled us to model SSVEP responses with contrast response functions. The results suggest that saccades primarily reduce response gain without significantly affecting contrast gain and that this reduction applies uniformly to both chromatic and luminance pathways. In summary, our study provides robust evidence that saccades similarly suppress visual processing in both the parvocellular and magnocellular pathways within the human early visual cortex, as indicated by SSVEP responses. The observation that saccadic eye movements impact response gain rather than contrast gain implies that they influence visual processing through a multiplicative mechanism.NEW & NOTEWORTHY The present study demonstrates that saccadic eye movements reduce the processing of both luminance and chromatic stimuli in the early visual cortex of humans. By modeling the contrast response function, the study further shows that saccades affect visual processing by reducing the response gain rather than altering the contrast gain, suggesting that a multiplicative mechanism of visual attenuation affects both parvocellular and magnocellular pathways.

Influence of aging on the color visual field in humans: A cross-sectional study

ABSTRACT

Age-related narrowing of the visual field is observed in the elderly, which leads to reduced cognitive and psychomotor functions. The aim of the present cross-sectional study was to determine the influence of aging on the visual field for color vision in humans, with respect to angular thresholds for object detection and color detection.The subjects were divided into the elderly group (mean 76.1-year-old [70-89]) and the control group (25.2 [18-47]). Visual fields for different colors (blue, green, yellow, and red) were measured by manual kinetic perimetry and evaluated in terms of 2 measures of visual-field width: angular thresholds for object detection and those for color detection.While angular thresholds for object detection were significantly wider than those for color detection in the control group (P < .001), there was no difference in the elderly group (P = .06). Moreover, angular thresholds for object detection were significantly wider in the control group than in the elderly group (P = .019), but angular thresholds for color detection were not significantly different between the 2 groups (P = .903).The observed age-related changes in angular thresholds for object detection in color vision may reflect an age-related reduction in rod function. Stable cone function might explain the preserved angular thresholds for color detection in the elderly.