Cortical mechanisms of normal and disordered human speech

About This Grant

This project will bring together a multidisciplinary team of neurosurgeons and systems neuroscientists – advised by experts in speech disorders – to investigate the neural dynamics relevant for speech planning in Parkinson’s disease (PD) and non-PD participants. We leverage previous work from our group in which we used electrocorticography (ECoG) to identify planning regions – including the caudal middle frontal gyrus (cMFG) during a question-answer task and a subsequent study in which perturbations of these sites with electrical stimulation resulted in speech planning deficits. The primary goal of the work is to uncover network mechanisms underlying speech planning and their relationship with larger scale cortical activity in normal speech and in individuals suffering from PD. To make progress on this issue, we will examine cortical activity during spoken interactions, focusing on both local and global neural responses. We will test the central hypothesis that PD can affect spoken language by disordering cortical planning dynamics. In Aim 1, we will investigate the large-scale activation of cortical networks during speech planning. We will compare responses of PD participants with an NIH-funded ECoG data set from individuals with normal speech to pinpoint networks affected by that disease. We will additionally employ advanced analytical methods to monitor the evolution of cortical responses during the planning process in normal and PD-affected speech. In Aim 2, we will use high-density ECoG to further characterize speech planning activity in cMFG. We will map the functional boundaries of cMFG and carry out a range of behavioral experiments to distinguish planning activity from nearby eye- and hand-movement control center responses, comparing our results across PD and non-PD patients. In Aim 3, we will dissect cMFG responses at the neural circuit level. Using a novel ultrahigh-density recording device, we will analyze the extent to which speech planning activity can be related to circuit hypotheses of motor planning. We will also examine the correlational structure of simultaneously recorded single units to gauge the impact of PD on cMFG circuit architecture. From our studies, we will investigate the cortical responses in normal and disordered speech planning with the broader goal of informing future therapeutic interventions designed to address clinical conditions affecting spoken language.