Use of a genetic algorithm for the analysis of eye movements from the linear vestibulo-ocular reflex

It is common in vestibular and oculomotor testing to use a single-frequency (sine) or combination of frequencies [sum-of-sines (SOS)] stimulus for hea d or target motion. The resulting eye movements typically contain a smooth tracking component, which follows the stimulus, in which are interspersed r apid eye movements (saccades or fast phases). The parameters of the smooth tracking - the amplitude and phase of each component frequency - are of int erest; many methods have been devised that attempt to identify and remove t he fast eye movements from the smooth. We describe a new approach to this p roblem, tailored to both single-frequency and sum-of-sines stimulation of t he human linear vestibulo-ocular reflex. An approximate derivative is used to identify fast movements, which are then omitted from further analysis. T he remaining points form a series of smooth tracking segments. A genetic al gorithm is used to fit these segments together to form a smooth (but discon nected) wave form, by iteratively removing biases due to the missing fast p hases. A genetic algorithm is an iterative optimization procedure; it provi des a basis for extending this approach to more complex stimulus-response s ituations. In the SOS case, the genetic algorithm estimates the amplitude a nd phase values of the component frequencies as well as removing biases. (C ) 2001 Biomedical Engineering Society.