Precise sound characteristics drive plasticity in the primary auditory cortex with VNS-sound pairing

IntroductionRepeatedly pairing a tone with vagus nerve stimulation (VNS) alters frequency tuning across the auditory pathway. Pairing VNS with speech sounds selectively enhances the primary auditory cortex response to the paired sounds. It is not yet known how altering the speech sounds paired with VNS alters responses. In this study, we test the hypothesis that the sounds that are presented and paired with VNS will influence the neural plasticity observed following VNS-sound pairing.MethodsTo explore the relationship between acoustic experience and neural plasticity, responses were recorded from primary auditory cortex (A1) after VNS was repeatedly paired with the speech sounds ‘rad’ and ‘lad’ or paired with only the speech sound ‘rad’ while ‘lad’ was an unpaired background sound.ResultsPairing both sounds with VNS increased the response strength and neural discriminability of the paired sounds in the primary auditory cortex. Surprisingly, pairing only ‘rad’ with VNS did not alter A1 responses.DiscussionThese results suggest that the specific acoustic contrasts associated with VNS can powerfully shape neural activity in the auditory pathway. Methods to promote plasticity in the central auditory system represent a new therapeutic avenue to treat auditory processing disorders. Understanding how different sound contrasts and neural activity patterns shape plasticity could have important clinical implications

A suite of automated tools to quantify hand and wrist motor function after cervical spinal cord injury

Abstract Background Cervical spinal cord injury (cSCI) often causes chronic upper extremity disability. Reliable measurement of arm function is critical for development of therapies to improve recovery after cSCI. In this study, we report a suite of automated rehabilitative tools to allow simple, quantitative assessment of hand and wrist motor function. Methods We measured range of motion and force production using these devices in cSCI participants with a range of upper limb disability and in neurologically intact participants at two time points separated by approximately 4 months. Additionally, we determined whether measures collected with the rehabilitative tools correlated with standard upper limb assessments, including the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) and the Jebsen Hand Function Test (JHFT). Results We find that the rehabilitative devices are useful to provide assessment of upper limb function in physical units over time in SCI participants and are well-correlated with standard assessments. Conclusions These results indicate that these tools represent a reliable system for longitudinal evaluation of upper extremity function after cSCI and may provide a framework to assess the efficacy of strategies aimed at improving recovery of upper limb function