Opportunities, pitfalls and trade-offs in designing protocols for measuring the neural correlates of speech. (September 2022)

• Record Type: Journal Article
• Authors: Cooney, Ciaran; Folli, Raffaella; Coyle, Damien
• Is Part Of: Neuroscience and biobehavioral reviews. Volume 140(2022)
• Publication Date: 2022-09
• Subjects: Speech decoding -- Brain-computer interfaces -- Imagined speech -- Overt speech -- EEG -- ECoG -- Experimental design -- Protocol -- Speech perception vs production; Psychophysiology -- Periodicals; Human behavior -- Periodicals; Animal behavior -- Periodicals; Neurology -- Periodicals; Behavior -- Periodicals; Ethology -- Periodicals; Neurology -- Periodicals; Psychophysiologie -- Périodiques; Comportement humain -- Périodiques; Animaux -- Mœurs et comportement -- Périodiques; Neurologie -- Périodiques; Animal behavior; Human behavior; Neurology; Psychophysiology; Periodicals; Electronic journals; 573.8
• DOI: 10.1016/j.neubiorev.2022.104783
• Languages: English
• ISSNs: 0149-7634

Abstract

Abstract: Decoding speech and speech-related processes directly from the human brain has intensified in studies over recent years as such a decoder has the potential to positively impact people with limited communication capacity due to disease or injury. Additionally, it can present entirely new forms of human-computer interaction and human-machine communication in general and facilitate better neuroscientific understanding of speech processes. Here, we synthesize the literature on neural speech decoding pertaining to how speech decoding experiments have been conducted, coalescing around a necessity for thoughtful experimental design aimed at specific research goals, and robust procedures for evaluating speech decoding paradigms. We examine the use of different modalities for presenting stimuli to participants, methods for construction of paradigms including timings and speech rhythms, and possible linguistic considerations. In addition, novel methods for eliciting naturalistic speech and validating imagined speech task performance in experimental settings are presented based on recent research. We also describe the multitude of terms used to instruct participants on how to produce imagined speech during experiments and propose methods for investigating the effect of these terms on imagined speech decoding. We demonstrate that the range of experimental procedures used in neural speech decoding studies can have unintended consequences which can impact upon the efficacy of the knowledge obtained. The review delineates the strengths and weaknesses of present approaches and poses methodological advances which we anticipate will enhance experimental design, and progress toward the optimal design of movement independent direct speech brain-computer interfaces. Highlights: Protocols for investigating neural speech decoding vary, with implications for understanding underlying correlates of speech. Various modalities are used to prompt speech, each associated with different stages of production and potential confounds. Novel designs inducing dialogic speech or ecological validation of task production enhance robustness and reproducibility. Linguistic features are not always included in experiments but can answer important questions for neural speech decoding. Use of experiments without thorough forethought for consequences on speech decoding limits comparison and meta-analysis.