Pairing Speech Sounds With Vagus Nerve Stimulation Drives Stimulus-specific Cortical Plasticity.
BACKGROUND
Individuals with communication disorders, such as aphasia, exhibit weak auditory cortex responses to speech sounds and language impairments. Previous studies have demonstrated that pairing vagus nerve stimulation (VNS) with tones or tone trains can enhance both the spectral and temporal processing of sounds in auditory cortex, and can be used to reverse pathological primary auditory cortex (A1) plasticity in a rodent model of chronic tinnitus.


OBJECTIVE
We predicted that pairing VNS with speech sounds would strengthen the A1 response to the paired speech sounds.


METHODS
The speech sounds 'rad' and 'lad' were paired with VNS three hundred times per day for twenty days. A1 responses to both paired and novel speech sounds were recorded 24 h after the last VNS pairing session in anesthetized rats. Response strength, latency and neurometric decoding were compared between VNS speech paired and control rats.


RESULTS
Our results show that VNS paired with speech sounds strengthened the auditory cortex response to the paired sounds, but did not strengthen the amplitude of the response to novel speech sounds. Responses to the paired sounds were faster and less variable in VNS speech paired rats compared to control rats. Neural plasticity that was specific to the frequency, intensity, and temporal characteristics of the paired speech sounds resulted in enhanced neural detection.


CONCLUSIONS
VNS speech sound pairing provides a novel method to enhance speech sound processing in the central auditory system. Delivery of VNS during speech therapy could improve outcomes in individuals with receptive language deficits.
School of Behavioral and Brain Sciences, The University of Texas at Dallas, 800 West Campbell Road GR41, Richardson, TX 75080, USA. Electronic address: novitski@utdallas.edu.
Crystal T
CT
Engineer
School of Behavioral and Brain Sciences, The University of Texas at Dallas, 800 West Campbell Road GR41, Richardson, TX 75080, USA; MicroTransponder Inc., 2802 Flintrock Trace Suite 225, Austin, TX 78738, USA.
Navzer D
ND
Engineer
School of Behavioral and Brain Sciences, The University of Texas at Dallas, 800 West Campbell Road GR41, Richardson, TX 75080, USA.
Jonathan R
JR
Riley
School of Behavioral and Brain Sciences, The University of Texas at Dallas, 800 West Campbell Road GR41, Richardson, TX 75080, USA.
Jonathan D
JD
Seale
School of Behavioral and Brain Sciences, The University of Texas at Dallas, 800 West Campbell Road GR41, Richardson, TX 75080, USA; Texas Biomedical Device Center, The University of Texas at Dallas, 800 West Campbell Road EC39, Richardson, TX 75080, USA.
Michael P
MP
Kilgard
D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D005260:Female; D006311:Hearing Disorders / Q000628:therapy; D006801:Humans; D009473:Neuronal Plasticity / Q000502:physiology*; D010700:Phonetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013064:Speech Disorders / Q000628:therapy; D055536:Vagus Nerve Stimulation
Plasticity; Primary auditory cortex; Speech; Vagal nerve stimulation