Extracting duration information in a picture category decoding task using hidden Markov Models

Abstract

Objective Adapting classifiers for the purpose of brain signal decoding is a major challenge in brain–computer-interface (BCI) research. In a previous study we showed in principle that hidden Markov models (HMM) are a suitable alternative to the well-studied static classifiers. However, since we investigated a rather straightforward task, advantages from modeling of the signal could not be assessed. Approach Here, we investigate a more complex data set in order to find out to what extent HMMs, as a dynamic classifier, can provide useful additional information. We show for a visual decoding problem that besides category information, HMMs can simultaneously decode picture duration without an additional training required. This decoding is based on a strong correlation that we found between picture duration and the behavior of the Viterbi paths. Main results Decoding accuracies of up to 80% could be obtained for category and duration decoding with a single classifier trained on category information only. Significance The extraction of multiple types of information using a single classifier enables the processing of more complex problems, while preserving good training results even on small databases. Therefore, it provides a convenient framework for online real-life BCI utilizations.

Hidden Markov model based continuous decoding of finger movements with prior knowledge incorporation using bi-gram models

“…In previous studies we demonstrated beneficial properties of hidden Markov models (HMMs) in the context of BCI decoding [1,2]. So far, the majority of studies covering the use of HMMs for BCI decoding (including ours) have focused on offline (e.g.…”