AUTHOR=Carvalho Vinícius Rezende , Mendes Eduardo Mazoni Andrade Marçal , Fallah Aria , Sejnowski Terrence J. , Comstock Lindy , Lainscsek Claudia TITLE=Decoding imagined speech with delay differential analysis JOURNAL=Frontiers in Human Neuroscience VOLUME=18 YEAR=2024 URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2024.1398065 DOI=10.3389/fnhum.2024.1398065 ISSN=1662-5161 ABSTRACT=

Speech decoding from non-invasive EEG signals can achieve relatively high accuracy (70–80%) for strictly delimited classification tasks, but for more complex tasks non-invasive speech decoding typically yields a 20–50% classification accuracy. However, decoder generalization, or how well algorithms perform objectively across datasets, is complicated by the small size and heterogeneity of existing EEG datasets. Furthermore, the limited availability of open access code hampers a comparison between methods. This study explores the application of a novel non-linear method for signal processing, delay differential analysis (DDA), to speech decoding. We provide a systematic evaluation of its performance on two public imagined speech decoding datasets relative to all publicly available deep learning methods. The results support DDA as a compelling alternative or complementary approach to deep learning methods for speech decoding. DDA is a fast and efficient time-domain open-source method that fits data using only few strong features and does not require extensive preprocessing.