# Miniature brain encodes optomotor response behavior in tiny thrips

## TL;DR

Tiny thrips with miniature brains and few eye units still show complex visual behaviors to compensate for visual limitations.

## Contribution

The study reveals how extreme miniaturization in thrips maintains optomotor behavior using simplified visual systems.

## Key findings

- Thrips have large interommatidial and photoreceptor acceptance angles of ∼18°, limiting object recognition.
- Thrips exhibit optomotor behavior by walking in circular paths to compensate for retinal slip during visual stimulation.
- The movement detection in thrips has a 41 ms temporal delay, suggesting elementary motion detection strategies.

## Abstract

Miniaturization of insects requires a reduction and simplification of morphological and physiological systems. An extreme example is the visual system of tiny thrips that has only 120 ommatidia and a tiny brain for image processing. To investigate the significance of this reduction, our study combines measurements of optical properties of ommatidia using micro-tomography with a behavioral assay on optomotor response and numerical analyses on the movement detector. We found large interommatidial and photoreceptor acceptance angles of ∼18°. During stimulation by a rotating stripe pattern, thrips walk on circular paths to compensate for retinal slip. We estimated ∼3.5 Hz stimulus temporal frequency for maximum optomotor response and ∼41 ms time constant for the low-pass filter of the movement detector. Our study suggests that even animals with an extreme miniaturization of their sensory systems maintain optomotor behaviors and possibly neural coding strategies of visual information that are typical for larger insects.

•Tiny brain and small number of ommatidia limit vision in miniature thrips•Object recognition is hampered by large interommatidial and acceptance angles of 18°•Thrips show vision-mediated optomotor behavior even at reduced visual capacity•The behavior results from elementary motion detection with a 41 ms temporal delay

Tiny brain and small number of ommatidia limit vision in miniature thrips

Object recognition is hampered by large interommatidial and acceptance angles of 18°

Thrips show vision-mediated optomotor behavior even at reduced visual capacity

The behavior results from elementary motion detection with a 41 ms temporal delay

Molecular neuroscience; Developmental neuroscience; Systems neuroscience