The Effect of Infrasound Exposure on Drosophila melanogaster

Infrasound is defined as any sound with a frequency below the threshold of human hearing (about 20 hz).  It has been linked to a stress response in many organisms, which could  seriously affect an organism's central nervous system.   This is particularly concerning because infrasound is produced in abundance by common phenomena. The experiment tested the correlation between the length of infrasound exposure and learning in Drosophila melanogaster.  Drosophila was used as a test subject for this experiment due to their major cochlear similarities to humans.  It was hypothesised that as the length of exposure increased, the learning in the flies would decrease.

Four experimental groups of 100 flies were used in the experiment,  all which were exposed to 16 hz sine wave at 100 dB for 0, 3, 7, and 24 hrs a day for 5 days  At the end of the five days the fly’s ability to learn to avoid a desirable scent was tested in a t-maze.  A pre-training score was taken of what percentage of the flies naturally avoided the scent.  The flies were then trained to avoid the scent using shaking as reinforcement. Finally, a post training score was taken.  These scores were used to calculate a percent learning index.  Two successful trials were conducted.

Analysis suggests that the initial hypothesis is valid, however all lengths of exposure used in this experiment statistically yielded the same impairment in learning, a reduction of 25-30%. Unexpectedly, the exposure time appears to have a significant impact on pre-training vinegar avoidance score, which may indicate a serious impairment in the olfactory system, chemoreceptors, and/ or Johnston's organs.  It may also be indicative of severe CNS damage.

Further experimentation should be conducted to differentiate between the impacts of physical damage and neurologic impairment on the learning index.