Vomiting is a common side effect of
cancer chemotherapy and many
drug treatments and diseases. In animal studies, the measurement of
vomiting usually requires direct observation, which is time consuming and often lacks temporal precision.
Musk shrews have been used to study the neurobiology of
emesis and have a rapid
emetic episode (∼1 s for a sequence of retching and expulsion). The aim of the current study was to develop a method to automatically detect and characterize
emetic episodes induced by the
cancer chemotherapy agent cisplatin. The body contour in each video frame was tracked and normalized to a parameterized shape basis. The tracked shape was projected to a feature space that maximized the shape variations in the consecutive frames during retching. The resulting one dimensional projection was sufficient to detect most
emetic episodes in the acute (peak at 2h) and delayed (peak at 54 h) phases after
cisplatin treatment.
Emetic episodes were relatively invariant in the number of retches (∼6.2), duration (∼1.2s), inter-retch interval (∼198 ms), and amplitude during the 72 h after
cisplatin treatment. This approach should open a new vista into
emesis research to permit tracking and analysis of
emesis in a small animal model and facilitate the development of new
antiemetic therapies. These results also yield a better understanding of the brain's central pattern generator for
emesis and indicate that the retching response in the
musk shrew (at ∼5.4 Hz) is the fastest ever recorded in a free-moving animal.