Non-fluent speech following stroke is caused by impaired efference copy

ABSTRACT

Efference copy is a cognitive mechanism argued to be critical for initiating and monitoring speech: however, the extent to which breakdown of efference copy mechanisms impact speech production is unclear. This study examined the best mechanistic predictors of non-fluent speech among 88 stroke survivors. Objective speech fluency measures were subjected to a principal component analysis (PCA). The primary PCA factor was then entered into a multiple stepwise linear regression analysis as the dependent variable, with a set of independent mechanistic variables. Participants’ ability to mimic audio-visual speech (“speech entrainment response”) was the best independent predictor of non-fluent speech. We suggest that this “speech entrainment” factor reflects integrity of internal monitoring (i.e., efference copy) of speech production, which affects speech initiation and maintenance. Results support models of normal speech production and suggest that therapy focused on speech initiation and maintenance may improve speech fluency for individuals with chronic non-fluent aphasia post stroke.

KEYWORDS:

• Aphasia
• efference copy
• speech entrainment
• speech fluency
• stroke

Acknowledgments

Portions of this study were presented at the annual Conference of Neurobiology of Language, London, UK, 2016, as part of a post-doctoral fellowship at the Medical University of South Carolina and University of South Carolina. We thank the Aphasia lab graduate students for assistance with data measurement.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Alexandra Basilakos http://orcid.org/0000-0003-0053-1082

Brielle Stark http://orcid.org/0000-0002-7001-8324

Additional information

Funding

This research was supported by the National Institutes of Health/National Institute on Deafness and Other Communication Disorders (NIH/NIDCD) [grant number P50DC014664-02 to Julius Fridriksson], [grant number DC14021 to Leonardo Bonilha], [grant number T32 DC014435 to Alexandra Basilakos]; and the American Heart Association [grant number SFDR N26030003 to Leonardo Bonilha].