Researchers at The University of Texas Health Science Center at San Antonio recorded changes in the neuromuscular junction synapses of aging fruit flies. These synapses are spaces where neurons exchange electrical signals to enable motor functions such as walking and smiling. "We observed a change in the synapse, indicating that the homeostatic mechanism had adjusted to maintain a new set point in the older animal," lead author Rebekah Mahoney said. The change was nearly 200 percent, and the researchers predicted that it would leave muscles more vulnerable to exhaustion. Videos obtained from the researchers show young and old fruit flies. One video is of a seven-day-old female and the other is of a 42-day-old female. These videos show the differences in motor function. The activity of the legs is significantly diminished in the older fly as is the extension of the proboscis, the body part that is used to suck up food and water.