An ethologically relevant paradigm to assess visual contrast sensitivity in rodents

Area of Science:

• Neuroscience
• Vision Science
• Animal Behavior

Background:

• The subcortical visual pathway is crucial for rapid threat detection and fear responses.
• Looming-evoked behaviors in rodents model instinctive defensive actions against aerial predators.
• The impact of contrast on looming-induced responses remains unexplored in rats and mice.

Approach:

• Investigated the effect of dark disk/gray background contrast on rat and mouse defensive behaviors in a looming arena.
• Analyzed contrast-dependent responses in relation to sex, age, and retinal ischemia.
• Utilized genetically modified mice and an age-related macular degeneration model to assess the roles of specific retinal cells.

Key Points:

• Rat and mouse defensive responses to looming stimuli exhibit a sigmoid relationship with disk/background contrast.
• Sex and age significantly influence contrast-dependent defensive behaviors.
• Retinal ischemia dampens contrast-dependent responses in rats.
• Cones, rods, and intrinsically photoresponsive retinal ganglion cells (ipRGCs) differentially contribute to contrast-dependent responses, with cones and rods being most critical.

Conclusions:

• Contrast is a critical factor modulating instinctive defensive behaviors in rodents.
• The visual system's contrast sensitivity, particularly via cones and rods, is essential for appropriate threat perception and behavioral responses.
• Findings elucidate the neural mechanisms underlying visual threat detection and have implications for understanding visual processing disorders.