The velocity of objects traveling along compound trajectories affects firing properties of an identified locust motion-sensitive interneuron
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1
University of Saskatchewan, Biology, Canada
The descending contralateral movement detector (DCMD) is a neuron in the locust visual system that is implicated in controlling escape behavior and is known to encode a ratio of the size and velocity of an object approaching along a single, collision trajectory. Recent studies suggest that the DCMD is also capable of encoding more complex visual information resulting from objects that transition to or from looming trajectories. However, the putative effects of object velocity have not yet been tested for these compound trajectories. We presented locusts with objects moving at different velocities along trajectories that transition to looming within different regions of the locust’s visual field. Concomitant extracellular DCMD recordings were analyzed to determine if firing rate modulation was correlated with disc expansion properties that reflect transition time and location. Transient translating to looming stimuli evoked two local maxima in firing rate- an early, broad and low peak that was followed by a decrease in firing rate associated with the time of transition between translating and looming, increasing in to a higher, primary peak just before the projected time of collision. The characteristics of the primary peak are consistent with the previously reported response of the DCMD to a looming visual stimulus; the timing of the peak was closer to the time of collision and the peak was narrower for higher velocity objects. Novel results show a correlation between the timing of the temporary decrease in firing rate and the time of transition for high velocity objects, but not for lower velocities. In addition, the difference between the height of the early peak and the depth of the following valley was less for objects travelling at higher velocities. These results, among others, may indicate that the DCMD is able to encode more visual information than previously though. In particular, this seems to be the case for objects moving at higher velocities, which would require a more immediate behavioural response in the natural environment of a flying locust.
Keywords:
insect,
Locust,
motion detection,
Vision
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster Presentation (see alternatives below as well)
Topic:
Sensory: Vision
Citation:
Gray
J and
Dick
P
(2012). The velocity of objects traveling along compound trajectories affects firing properties of an identified locust motion-sensitive interneuron.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00353
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Jack Gray, University of Saskatchewan, Biology, Saskatoon, Canada, jack.gray@usask.ca