Measures of complexity in neural spike-trains of the slowly adapting stretch receptor organs

Discrete sequence analysis methods were applied to study spike-trains gener ated by the isolated neuron of the slowly adapting stretch receptor organ. Calculation of the algorithmic complexity and block entropies of digitized individual spike-train forms allowed us to distinguish different classes of neural behavior. While some spike-trains exhibited significant structure, others displayed diverse degrees of randomness. The sequences recorded duri ng the stimulated portions of the intermittent and walk-through forms, diff ered considerably from their randomly shuffled surrogates. Informational an d grammar complexity measures (in two, four and eight-letter alphabets), te ll us things about the structure of spike-trains that are not obtained, wit h conventional spike analysis. Comparison of the conditional entropies for the digitized signals showed that the method distinguishes between differen t stimulated conditions. Additionally, comparison of the different stimulat ed conditions with their corresponding surrogates showed that, both, condit ional entropies and complexities were significantly different for the two g roups. Although the original and the randomly shuffled sequences had the sa me distribution and average firing rate, their complexity values were diffe rent. The results obtained with both measures of sequence structure were qu ite consistent (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.