Comparative approaches to escape

- Visual looming stimuli trigger escape and defensive behaviors in animals across phyla.
- Loom-evoked escapes comprise sequences of behaviors with both stereotyped and flexible elements.
- Neural encoding of looming stimuli is remarkably similar across species.
- Escape motor patterns depend on relative spike timing between descending pathways.
- Loom-initiated persistent internal states can be studied in invertebrates and may underlie fear.

Neural circuits mediating visually evoked escape behaviors are promising systems in which to dissect the neural basis of behavior. Behavioral responses to predator-like looming stimuli, and their underlying neural computations, are remarkably similar across species. Recently, genetic tools have been applied in this classical paradigm, revealing novel non-cortical pathways that connect loom processing to defensive behaviors in mammals and demonstrating that loom encoding models from locusts also fit vertebrate neural responses. In both invertebrates and vertebrates, relative spike-timing in descending pathways is a mechanism for escape behavior choice. Current findings suggest that experimentally tractable systems, such as Drosophila, may be applicable models for sensorimotor processing and persistent states in higher organisms.