Increased surround modulation of perceived contrast in the elderly

Area of Science:

• Visual perception
• Human aging
• Sensory neuroscience

Background:

• Stimulus appearance is influenced by background contrast, with high-contrast backgrounds reducing perceived contrast.
• Older adults exhibit heightened perceptual surround suppression compared to younger individuals.
• This study investigates if age-related differences in brightness induction mechanisms, sensitive to phase information, underlie enhanced surround suppression.

Purpose of the Study:

• To determine if age-dependent differences in phase-sensitive brightness induction mechanisms cause enhanced surround suppression in the elderly.
• To compare perceived contrast in younger and older adults under conditions of varying surround contrast and phase.

Main Methods:

• A method of constant stimuli was employed to measure perceived contrast in 15 younger (18-33 years) and 18 older (61-84 years) adults.
• Participants viewed a central sine wave grating with an annular surround, either in-phase (suppressive) or out-of-phase (enhancive).
• Stimulus contrast was adjusted for younger observers to match the detection contrast of older adults to isolate surround effects.

Main Results:

• Older adults reported lower perceived contrast with a surround compared to younger adults (p < 0.001).
• The magnitude of contrast suppression differences between age groups was consistent regardless of annulus grating phase (p = 0.85).
• Age-related differences in suppression remained similar even when stimulus contrast was adjusted to equate detection levels (p = 0.81).

Conclusions:

• Normal aging leads to increased perceived contrast surround suppression, independent of stimulus border phase information.
• Visual conditions that enhance perceived contrast in younger adults result in suppression among the elderly.
• These findings suggest age-related visual perception changes impact object appearance in natural, variable-contrast environments.