Date of Award

6-2008

Document Type

Union College Only

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Robert Olberg

Language

English

Keywords

spike, neurons, higher, spikes, stimulus

Abstract

The predatory interception of prey by dragonflies is controlled by a highly developed visual system. The responses of giant interneurons in the central nervous system known to control this behavior have only been investigated in the lab under artificial lighting. Our setup moved the dragonfly system outside into its natural habitat. This resulted in much greater light intensity including UV and higher temperatures. Beads of three sizes were moved in front of a dragonfly as a stimulus. The motion of the bead was reconstructed in three dimensions allowing us to relate neural activity with bead position, direction, and speed. Results show that visual neurons in the CNS behave much differently at higher, outdoor temperatures. We found a remarkable decrease in spike width along with spike frequencies far exceeding those exhibited in the lab at these high temperatures. Movement of the wings requires spike frequencies of 200Hz, but it appears that in the dragonfly’s natural habitat the average spike frequency is actually much higher than this. There is also potential for correlation between spikes as represented by consistent time differences between the spikes of two neurons. If correlation occurred this would indicate a potential for increased information content in the spike trains. The timing between the spikes of two neurons could convey meaningful information about the stimulus. When combined with the three-dimensional reconstruction of the stimulus, we can learn more about the receptive fields of these neurons when they fire independently as well as when they exhibit correlated responses.

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