Apparent Motion Perception in the Praying Mantis: Psychophysics and Modelling.

Area of Science:

• Neuroscience
• Comparative vision research
• Insect behavior

Background:

• Apparent motion perception relies on discriminating object displacement between still frames.
• Human motion perception has a lower bound (Dmax) for displacement, scaling with element size.
• Insect motion perception mechanisms, particularly Dmax scaling, remain less understood.

Purpose of the Study:

• To investigate how the maximum displacement limit (Dmax) for apparent motion perception scales with element size in the praying mantis (Sphodromantis lineola).
• To compare motion perception scaling in mantises with that of humans.
• To develop models explaining Dmax scaling in insect vision.

Main Methods:

• Eliciting optomotor response in mantises using random chequerboard patterns with varying element and displacement sizes.
• Calculating Dmax as the displacement step size for a 50% probability of directional optomotor response.
• Developing and testing computational models (motion energy and Reichardt Detector) to explain observed scaling.

Main Results:

• Mantis Dmax scales approximately with the square-root of element size.
• Unlike humans, mantis Dmax is not lower-bounded.
• Computational models successfully explain the observed Dmax scaling in mantises.

Conclusions:

• Insect motion perception, exemplified by mantises, appears limited by a single spatial filtering stage, consistent with compound eye optics.
• Human motion perception involves an additional spatial filtering stage, likely the magnocellular pathway, occurring at coarser scales than human optics.
• Despite differences in filtering stages, mantis and human apparent motion perception and Dmax are qualitatively similar after these filtering processes.