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The Flight Trace III: Combined Evaluation

Since torque trace and position trace are measured simultaneously, the torque trace can be used to calculate the effects of torque on arena position.

Angular Displacement Size. As another measure of spike dynamics the angular displacement during each detected spike is calculated by the distance between two position-data points in degrees, the corresponding torque values of which denote the duration of the spike (Fig. 10).

Stepwise Arena Rotation. As a quantitative measure for the subjective impression of sudden arena rotations accounted for by spikes, the sum of angular displacements during spikes is compared to the sum of interspike displacement for each 2 min. period in a rotation index: (rs-ri)/(rs+ri), where rs denotes the sum of angular displacement during the spikes and ri the sum of arena displacements between two spikes.

Spike Detection Efficiency

A subjective test for spike detection efficiency was performed with five members of the lab, only one of whom was familiar with Drosophila's body saccades: they were presented with the task to count the number of spikes in the torque traces of four deliberately chosen flies. The mean number of detected spikes in the first three periods was compared to the number the spike detector counted. Two of the flies were deemed to be 'regular' flies producing spikes that were very easy to distinguish from the torque baseline. The third fly was flying in the 'oscillating' mode and the fourth fly in the 'quiet' mode.

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