Abstract
The Buridan’s paradigm is a behavioral task designed for testing visuomotor responses or phototaxis in fruit fly Drosophila melanogaster. In the task, a wing-shortened fruit fly freely moves on a round platform surrounded by a 360° white screen with two vertical black stripes placed at 0° and 180°. A normal fly will tend to approach the stripes one at a time and move back and forth between them. A variety of tasks developed based on the Buridan’s paradigm were designed to test other cognitive functions such as visual spatial memory. Although the movement patterns and the behavioral preferences of the flies in the Buridan’s or similar tasks have been extensively studies a few decades ago, the protocol and experimental settings are markedly different from what are used today. We revisited the Buridan’s paradigm and systematically investigated the approach behavior of fruit flies under different stimulus settings. While early studies revealed an edge-fixation behavior for a wide stripe in the initial visuomotor responses, we did not discover such tendency in the Buridan’s paradigm when observing a longer-term behavior up to minutes, a memory-task relevant time scale. Instead, we observed robust negative photoaxis in which the flies approached the central part of the dark stripes of all sizes. In addition, we found that stripes of 20°-30° width yielded the best performance of approach. We further varied the luminance of the stripes and the background screen, and discovered that the performance depended on the luminance ratio between the stripes and the screen. Our study provided useful information for designing and optimizing the Buridan’s paradigm and other behavioral tasks that utilize the approach behavior.
Highlights
The fruit fly Drosophila melanogaster serves as a good animal model for behavioral studies because of its complex behavior and abundant genetic tools [1]
We systematically investigated the approach behavior with different stimulus settings at the time scale of minutes and revisited the question: what is the behavior preference of fruit flies in the Buridan’s paradigm? We tested the flies under three hypotheses for the behavioral preferences: (1) The flies prefer salient visual objects, (2) they are attracted by high-contrast edges, and (3) they like to approach dark regions
We introduced several behavior metrics that are more accurate in quantifying the detailed approach behavior than the metrics proposed earlier [9]
Summary
The fruit fly Drosophila melanogaster serves as a good animal model for behavioral studies because of its complex behavior and abundant genetic tools [1]. The movement patterns and behavioral preferences in the Buridan’s or similar tasks with different stimulus conditions were extensively investigated in 70’ and 80’ [5,6,7,10] Those studies were either focusing on the initial visuomotor responses at a time scale of seconds, or using different stimuli rather than two black stripes. In consequence, when we study the visual spatial memory of fruit flies at a time scale of minutes and use tasks that are developed based on the Buridan’s paradigm, the earlier results cannot provide sufficient metrics for comparison and optimization of the experimental setup. We systematically investigated the approach behavior with different stimulus settings at the time scale of minutes and revisited the question: what is the behavior preference of fruit flies in the Buridan’s paradigm? This was a previously un-explored experimental setup but critically affected the optimization of experimental apparatus
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