A METHOD FOR MOTION COMPENSATION OF A MOVING NEMATODE CAENORHABDITIS-ELEGANS AND ITS APPLICATION TO FREQUENCY-ANALYSIS OF PHARYNGEAL PULSATION

A new sequential image processing method for motion compensation of a moving object with stringy shape has been developed for estimating the pharyngeal pulsation of the nematode Caenorhabditis elegans under sev eral environmental conditions. The method is based on the pixel data t ransfer on a new image frame while changing the boundary shape and the position but preserving the conformation of the inner structure of an object. All digitized image frames of C. elegans were first converted to motion-compensated images to arrange the pulsation site in the sam e region of the every transformed frame. The pulsation site was then a utomatically detected by determining the pixels where the temporal bri ghtness variation was much larger than that of the other pixels. Final ly, the pulsation frequency was determined by the Fourier analysis. Th e validity of our method has been confirmed by analyzing various test data, and the method has been applied for detecting the pharyngeal pul sation frequencies of C. elegans on some environmental conditions, i.e . feed bacteria-free/rich, doping of nerve inactivating ethyl-alcohol and nerve stimulant neurochemical substance of serotonin. The motion c ompensation method automatically provided reasonable pulsation frequen cies which were found to be comparable to those obtained by manual cou nting. Thus the method is useful for systematic investigations on the variation of pharyngeal pulsation associated with the activity change of the nervous system in environments. (C) 1998 Elsevier Science B.V. All rights reserved.