Dynamic Right Hemisphere Recruitment for Language
Our ability to understand linguistic function and dysfunction is contingent upon an improved understanding of how language processes are distributed in the intact brain, and how resources are allocated as a function of the ever changing demands. This project,funded by the National Institute on Deafness and other Communication Disorders, applies TMS, fMRI, and concurrent TMS/fMRI investigations to explore a new hypothesis about the dynamic roles of the two cerebral hemispheres in normal language processes and implications for recovery of function following unilateral brain damage. Our hypothesis in brief is that the right hemisphere (RH) becomes engaged in a variety of linguistic tasks when the processing demands of the task outstrip the resources available in the dominant left hemisphere (LH) and some of the residual processing “spills over” into RH homologues (e.g., Just & Varma, 2007; Prat, Mason, & Just, 2011). Importantly, the spillover hypothesis predicts that RH involvement varies across tasks and individuals, as a function of the relation between cognitive and neural resources available to an individual and of the demands required to complete the task. Recovery from unilateral brain damage is likely to vary as a function of pre-injury lateralization; therefore our understanding of the factors related to individual differences in language lateralization is imperative. One goal of this project is to obtain knowledge about the causes and correlates of individual differences in language laterality. Another is to investigate system-level characteristics of the cortical network responsible for language processes, and how they relate to individual language lateralization and skill. A final goal is to investigate how the language network changes as a whole in response to impaired functioning in isolated regions. This information will further our understanding of how the two hemispheres cooperate during intact language processes, and ultimately improve our understanding of deficits associated with unilateral damage and how to enhance recovery.
Bilingual Brain Training
Speaking one language is, in itself, an amazing achievement. According to some estimates, however, almost half of the world population manages to be proficient in two or more different languages. Research shows that such mastering of multiple languages has profound effects an individual’s cognitive abilities, extending beyond social and communicative benefits. In fact, bilinguals outperform monolinguals in a variety of tasks that are cognitively demanding , such as those drawing on executive processes such as inhibitory control and working memory. In other words, speaking two languages seems to “train” the brain in a manner that has effects that generalize to non-language domains. Our current research at the CCDL is using “Dynamic Causal Modeling” of neuroimaging data, in combination with our existing understanding of the neural basis of individual differences in cognitive capabilities, to better understand the nature of the brain changes induced by bilingualism, and explain how this translates into a general cognitive benefit.
Instructions and Rule Application
Controlling one’s own actions according to predefined rules is an amazing feature of human behavior. It underlies human’s intelligence and flexibility, makes general knowledge possible, and enables planning. Importantly, it also makes it possible to communicate instructions (in the form of rules) using language (which is, in itself, a rule based skill). Though such rule-based behavior is central to flexible human thought, the precise neural mechanisms underlying rule acquisition, instantiation, and execution are still poorly understood. At the CCDL, we are trying to understand the process by which our brain encodes and interpret rules by using “Dynamic Causal Modeling” of neuroimaging data, and detailed computer models of the brain. We are also applying our knowledge to real-world scenarios, by devising methods that would improve how students understand mathematical rules, and using data from the brain to better understand the causes of their mistakes.
Cognitive Control and Language Production
Cognitive control or “the ability to behave in accord with rules, goals, or intentions, even when this runs counter to reflexive or otherwise highly compelling, competing responses” (Rougier et al., 2005, p. 7338) is an ability that is essential to humans in order to successfully perform daily tasks (like driving to the grocery store after work!). This ability is involved in many different aspects of our daily tasks including but not limited to problem-solving, switching from one task to another, decision-making, learning, and maintaining focus in the face of distraction. Cognitive control also appears to be associated with one’s ability to successfully produce language. However, the extent to which different aspects of cognitive control are related to language production remains unclear. At the CCDL, we are trying to further understand the causal relationship between various aspects of cognitive control and language production by using experimental manipulations during speech to determine whether specific aspects of cognitive control differentially impact language production in individuals with relative advantages and disadvantages in cognitive control.
Impulsivity and Inhibitory Control
People differ in their level of impulsivity – that is, how often they decide to act on a whim, or without considering the consequences of their decisions. Although healthy individuals vary in their degree of impulsivity, the trait is also a major component of various disorders, including ADHD, substance use disorders, and borderline personality disorder. Some types of impulsivity are related to poor inhibitory control, but the underlying cognitive and neural mechanisms of inhibition remain unclear. Because the broad construct of inhibition is understood to include multiple behavioral and neural processes, a complete mechanistic description of inhibitory control requires a behaviorally- and neurally-plausible model of inhibitory components. Current research at the CCDL is investigating a novel model of inhibition based on the presence of distinct time points of behavioral control. We are using both behavioral and neuroimaging data to evaluate this model. One major goal of this research is to evaluate the link between inhibitory control and impulsive tendencies. Ultimately, we hope to provide a foundation for biological, cognitive, and clinical descriptions of inhibitory control and impulsivity.
Non-Invasive Human Brain to Brain Interface
In 2013, together with Dr. Rajesh Rao and Dr. Chantel Prat, Dr. Stocco has demonstrated the possibility of transferring simple information directly between two brains using non-invasive brain stimulation devices. This pilot study has been extensively covered by the media.