Award details

Tuning of the preferred optic flow axes of locust and blowfly visual interneurons to their preferred modes of flight behaviour

Reference	BB/C007336/1
Principal Investigator / Supervisor	Professor Holger Krapp
Co-Investigators / Co-Supervisors	Professor Simon Laughlin
Institution	University of Cambridge
Department	Zoology
Funding type	Research
Value (£)	255,676
Status	Completed
Type	Research Grant
Start date	01/06/2005
End date	30/04/2006
Duration	11 months

Abstract

Optic flow is an important motion cue used by insects to stabilise and control flight. It is a global property of the vector field associated with self-motion, so specific optic flow must be detected by a neuron tuned to overall vector field topology. As optic flow depends on the insect¿s motion, we expect individual neurons to be tuned to different aspects of the insect¿s flight behaviour. The overall aim of this joint study is to test the hypothesis that the visual interneurons of insects are tuned to their preferred modes of flight behaviour, and to make inferences about the optimal design of biological computational systems linking sensory neurons and locomotor behaviour. Visual motion is sensed locally by elementary motion detectors. The local vector directions they sense are ambiguous in respect of self-motion and must be integrated to yield meaningful information on optic flow. This integration is done in blowflies by a group of about 60 individually identifiable tangential neurons of each lobula plate, 13 of which are known to connect to motor control centres. It is not known whether such specific optic flow integration occurs in other insects, especially those lacking the lobula plate (eg. locusts). A primary objective of this study is to map the response fields of visual interneurons of the locust Schistocerca gregaria for the first time and to compare them with the known response fields obtained from blowfly Calliphora vicina interneurons, by measuring the activity of individual neurons in response to local motion stimuli. A secondary objective is to verify that the resulting response fields reflect the neurons preference for specific wide-field stimuli, by recording their activity while projecting different optic flow fields onto an opaque dome surrounding the insect. These data will tell us the preferred axes of self-motion of the visual interneurons: a tertiary objective is then to record the activity of individual steering muscles in response to visual stimulation of individual visual interneurons. This data on preferred stimuli will be compared with data on preferred motions in flight. Some combinations of motion are more favourable for turning than others (eg. bank and yaw are usually combined in a banked turn). These preferred motions are inherent properties of dynamical systems, excited either as natural modes in response to accidental disturbance or as preferred turning modes in the course of voluntary manoeuvres. They can be determined quantitatively by solving equations of motion linking the insect¿s acceleration with the external forces and torques, and then compared with the neurons preferred axes. Equations of motion have been formulated empirically for locusts (with certain limitations) but are unknown for other insects. A primary objective of this study is to formulate the equations of motion of blowflies Calliphora for the first time, and to compare them with newly refined equations of motion for locusts Schistocerca. This will be done by tethering the insects to a 6-component force balance in a purpose-built flight simulator and measuring the dynamic forces and torques as we oscillate the insect, vary the speed or direction of airflow, or vary the optic flow fields projected on a dome around the insect. The preferred modes of flight behaviour of locusts and blowflies are also known partially from free flight studies, but even the best of these studies have imposed physical constraints on the insects. A secondary objective is therefore to obtain basic statistical information on turn radius and translation velocity in manoeuvring locusts and blowflies during unconstrained free flight. This will be done using high-speed stero-videography to obtain 3D trajectories and body kinematics. A tertiary objective is to measure the external torques generated by individual steering muscles and to link this to the optic flow fields stimulating the visual interneurons.

Summary

unavailable

Committee	Closed Committee - Animal Sciences (AS)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

Associated awards:

BB/C007336/2 Tuning of the preferred optic flow axes of locust and blowfly visual interneurons to their preferred modes of flight behaviour

BB/C518573/1 Tuning of the preferred optic flow axes of locust and blowfly visual interneurons to their preferred modes of flight behaviour

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