Use of stochastic grammars for hypnogram analysis

The hypnogram is a schematic representation of sleep dynamics as a sequence of stages along the night. In a sense, it is a model of the so called sleep macrostructure. This paper considers the hypnogram as expression of a language whose structure is to be analysed and modeled in terms of stochastic grammars. These are inferred using Crespi-Reghizzi´s method. A parsing algorithm, exploring the particular structure of the inferred grammars, has been developed. Classification strategies for both noisy and non-noisy patterns is also discussed. An example concerning a population of normals and a population of psychiatric (dysthymic) patients is presented