Symmetry activates extrastriate visual cortex in human and nonhuman primates

Area of Science:

• Neuroscience
• Visual Perception
• Cognitive Science

Background:

• Humans demonstrate a strong affinity for visual symmetry in their surroundings.
• Understanding the neural basis of symmetry perception is an emerging area of research.

Purpose of the Study:

• To investigate the brain mechanisms underlying the perception of visual symmetry.
• To determine if symmetry processing is specific to higher-order visual areas.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure brain activity in humans viewing symmetric versus random dot stimuli.
• Attention controls were implemented to isolate symmetry-specific responses.
• Stimuli included dot patterns, line-based figures, and varied sizes and configurations.
• fMRI was also employed in macaque visual cortex for comparative analysis.

Main Results:

• Symmetric stimuli elicited robust fMRI activity in human higher-order visual cortex (areas V3A, V4, V7, LO).
• This activity was independent of attention and strongly correlated with the subjective perception of symmetry.
• Similar responses were observed across different stimulus types, sizes, and configurations.
• Weaker, but detectable, symmetry-related activity was found in analogous regions of the macaque brain.

Conclusions:

• The human brain exhibits a specialized enhancement for processing visual symmetry, particularly in higher-order visual areas.
• The neural underpinnings of symmetry perception, while enhanced in humans, share commonalities with nonhuman primates.
• These findings contribute to understanding the neural basis of aesthetic appreciation and visual processing.