| During speech production, we make vocal tract movements with remarkable precision and speed. Starting with the earliest cortical stimulation studies, we have learned much about what brain regions are involved with speech motor control. However, our understanding of how activity in these regions gives rise to the movements made is limited, in part due to the challenge of simultaneously acquiring high-resolution neural recordings and detailed vocal tract measurements. A complete neurobiological understanding of speech motor control requires determination of the relationship between simultaneously recorded neural activity and the kinematics of the speech articulators (i.e, lips, jaw, and tongue). Recent advances in human electrophysiological recordings allow us to observe neural activity in these regions with unprecedented resolution, but without concurrently measuring the speech articulators it is difficult to interpret this activity. To overcome this challenge, we combined ultrasound and video monitoring of the supralaryngeal articulators (lips, jaw and tongue) with electrocorticographic (ECoG) recordings from the cortical surface to investigate how neural activity relates to measured articulator movement kinematics (position, speed, velocity, acceleration) during the production of English vowels. In this document, we first provide a review of the functional organization of primary speech motor cortex, also called ventral sensory motor cortex (vSMC). Next, we describe and validate methods for a noninvasive, multi-modal imaging system to monitor vocal tract kinematics that is compatible with bedside human neurophysiological recordings. Last, we use these methods to examine the relationship between activity in vSMC and the kinematics of speech articulator movements. These findings demonstrate novel insights into how articulatory kinematic parameters are encoded in vSMC during speech production. |
