Causal Role of Cortico-Cerebellar Networks in Working Memory
Working memory, the ability to temporarily retain information in mind, is a robust predictor of broader measures of cognitive ability, and its impairment is a cardinal feature of clinical conditions such as ADHD, schizophrenia, and dementia. This project aims to elucidate the causal influence of multiple areas spanning cerebellum and cerebral cortex on specific aspects of behavior and neural activity related to the persistent maintenance of information using a combination of fMRI and TMS. A more precise mechanistic understanding of the causal bases of working memory could motivate the development of novel interventions aimed at improving working memory in both healthy and pathological individuals.
Working Memory Adaptation
Our nervous system accounts for a continuously changing environment by building internal models of the body and world. Adaptation is the process by which we dynamically adjust these models in response to sensory feedback (Shadmehr, Smith & Krakauer, 2010). The vast majority of research on adaptation has examined adaptation in the context of motor control. In this study, we aim to determine whether locations stored in working memory are adapted in a similar manner to motor actions. If so, this would suggest that the computational principles governing the adaptive control of motor commands may similarly help to adjust and calibrate cognitive processes in response to novel environments
Modeling Cognitive Control via the Underlying Action Preparation Processes
Cogntive control refers to the set of processes that allow us to change and/or bias our behavior to better reach our goals in the moment. This often involves resisting our habitual and automatic actions to act in a more goal-directed way. Many studies have shown that in situations of habit-goal conflict, we are slower to act when measured with free response time (RT). However, the reliance on RT differences as a dependent measure has serious shortcomings that leaves it unclear which cognitive control process are at play in different situations: enhanced processing of goal-relevant information, inhibition of processing of goal-irrelevant information, globally enhanced processing speed, etc. Using methods developed in the motor control literature, we are investigating how re-conceptualizing cognitive control in terms of underlying the action selection process can improve our understanding of the specific cognitive control processes that are affected by reward and other variables.
The role of the dorsolateral prefrontal cortex in motor skill expertise
Activity and the network connections of cognitive control regions including dorsolateral prefrontal cortex (DLPFC) show marked reductions as expertise develops when measured with fMRI. This is usually taken as evidence of a reduced role in supporting performance. However, activity in motor cortex is seen as essential to performance even though its activity is also greatly reduced over the course of training. As neuroimaging is an inherently correlational technique, we are examining the causal role of both the DLPFC and primary motor cortex (M1) at different stages of motor skill learning by using a combination of multivariate fMRI techniques and TMS following six weeks of training on a motor sequencing task.
Parkinson’s Disease as a Model for Studying Cognitive-Motor Interactions
The most striking deficits in PD are motor: slowness of movement and trouble initiating movements resulting in gait and balance impairments. Recent work shows that some of these motor deficits in PD may be driven by changes in frontal cortical processing more typically associated with cognitive control functions. However, the evidence from human research linking disruption of an attention-motor interface (AMI) and motor deficits in PD is correlational: cognitively impaired individuals often also display gait and balance deficits. Professor Lee was recently awarded the Young Investigator Award from the Parkinson’s Foundation that will fully fund a three-year project proposing to perform strong causal tests of the AMI hypothesis using TMS. Different TMS protocols can be used to either focally suppress or enhance neuronal excitability in brain regions of interest. We will determine whether disrupting activity in a cognitive AMI node in frontal cortex will worsen motor deficits in PD and whether increasing excitability can lead to improvements in motor function.
Other Ongoing Research Projects
- The focus of attention on motor skill learning and performance
- Examining the neural mechanisms of choking under pressure
- And more!