Speech is a uniquely human trait that is central to our everyday lives, but the mechanisms that enable retrieval and formation of articulatory sequences remain elusive. Several lines of evidence suggest that the left inferior frontal gyrus (IFG), or Broca?s region, is active prior to articulation per se and critically supports articulatory planning. However, it remains unclear how different anatomical parcellations of IFG support retrieval of semantic information and articulatory planning. To investigate this issue, we will leverage resources at NYU, assembling clinicians and researchers with complementary expertise to reexamine the role of the IFG in speech. We propose working in a cohort of neurosurgical patients who provide a rare and unique opportunity to collect direct cortical recordings and perturbations during speech production. Specifically, we will address the following questions: (1) what is the time constant of neural responses across IFG in relation to speech production, (2) what is the functional specificity of IFG regions, pars opercularis and pars triangularis, and (3) what are the functional boundaries Broca?s territory across the left and right frontal cortices. To gain traction on these issues, we have developed a battery of speech production tasks that is designed to mirror clinical electrical stimulation mapping and provides a within subject functional and causal comparison. We will use standard and high density electrocorticography (ECoG) to measure responses with high temporal precision within IFG. To determine causality, we will manipulate cortical activity using direct cortical stimulation and examine changes in behavior, timing of speech deficits and comparing with ECoG functional responses. The outcome of this study will greatly advance our understanding of the neurophysiologic mechanisms underlying speech production with a long-term goal of addressing a range of speech disorders and improving current language mapping techniques.
The inferior frontal gyrus (IFG), or Broca?s area, is widely recognized to be important for speech production, but its specific role and temporal dynamics in supporting articulatory and semantic processing remains elusive. We propose a battery of speech production assays aimed at teasing apart aspects of neural activity involved in speech production. Using these tasks in tandem with high resolution recording and electrical perturbation techniques, we will greatly advance the knowledge of how IFG supports speech production in the hopes that our findings will inform new therapeutic strategies for a range of speech disorders as well as surgical approaches to language mapping.
