Tracy Research

Contact

Name: Joseph I. Tracy, PhD, ABPP/CN
Position: Director, Cognitive Neuroscience and Brain Mapping Laboratory; Director, Clinical Neuropsychology Division & Professor, Departments of Neurology & Radiology
Telephone: 215-955-4661
Tracy Laboratory

My lab focuses on functional and structural brain connectivity as measured by resting state functional connectivity, diffusion imaging, high-resolution anatomical MRI, and task-based functional magnetic resonance imaging. Applications to  understanding and modeling  the effects of seizures on cognitive networks are investigated, as well as  the change and reorganization such networks undergo in response to treatment interventions such as resective surgery, thermal ablation, and brain electrical stimulation. Additional research projects focus on the neuroimaging correlates of seizure development as a model of maladaptive plasticity in the brain. The neuropsychological correlates of brain structural and functional network organization are also studied. Imaging methods and analysis that aid in pre-surgical planning and the prediction of surgical outcomes in epilepsy and other neurologic disorders are tested, validated and implemented. The lab regularly conducts MR scans that provide maps of brain structure and function utilized in pre-surgical planning, and during intraoperative neuronavigation in the surgical suite. Over 150 pre-surgical brain mapping studies are performed per year. The research program provides research opportunities for graduate and medical school students. Collaborations are welcome. Current chief collaborators are Dr. Michael Sperling, M.D., Epileptologist and Dr. Ashwini Sharan, M.D., Neurosurgeon. Additional collaborators include: Christopher Skidmore, M.D., Epileptologist, Dr. Richard Gorniak, M.D., Radiologist, Dr. Xiaosong He,  Ph.D. (Post-doctoral Fellow), Chaitanya Ganne, Ph.D./M.D. (Post-Doctoral Fellow), and Dr. Karol Osipowicz, Ph.D., Neuroscientist (former Post-Doc in the lab).

Research Assistant Positions and Post-Doctoral Fellowships in Clinical Neuroimaging are offered.

Research Projects

Language Lateralization and Cognitive Reorganization in Epilepsy

I demonstrated that when language skills reorganize to the right hemisphere they show substantial independence, suggesting that component language skills do not shift in a monolithic fashion. I argued that the status of the healthy hippocampus plays a role in determining whether language reorganizes ipsilaterally or contralaterally. I published the first work demonstrating that resting state functional connectivity (rsFC) can be used to predict hemispheric language lateralization. I showed that the pathophysiology of seizures and epileptogenesis are neuroplastic processes, causing epilepsy patients to be highly prone to reorganization, showing that cognitive network change is a dynamic not static process.

Structural and Functional Connectivity in Epilepsy

I provided evidence for a “pruning” hypothesis to model the relation between task fMRI and functional connectivity. I presented evidence for considering focal epilepsies a network disorder. I have used rsFC to demonstrate that the build-up of seizure networks is not random and may, in some cases, be adaptive, generating an inhibitory surround to keep seizures focal. 

Memory Functioning in Epilepsy

I demonstrated that temporal lobe epilepsy demonstrates a dissociation between implicit (intact) and explicit (impaired) memory. Using rsFC, I was the first to show that the dorsal (not ventral) DMN bears the impact of TLE, interacting with the side of pathology. I demonstrated that the side of epilepsy pathology produces distinct FC effects, implying different capacities for cognitive reorganization and recovery.  

Prediction of Outcomes Following Epilepsy Surgery

In the first article using rsFC to predict outcome, I demonstrated that cognitive outcome was successfully predicted with 68% of the variance explained, with connections to the healthy hippocampus the most common predictor. I demonstrated that genuine reorganization of white matter tracks after ATL can implement inter-hemispheric shifts in language, with this associated with better surgical outcomes. I presented a conceptual framework for identifying and interpreting multi-modal neuroimaging studies of cognitive reorganization and recovery. 

Cognitive Reorganization from Learning

I reported that throughout  different stages of learning and a form of adaptation occurs, or a new functional circuit is formed with some structures dropping off and others joining. I argued that strong learning of a complex motor task generates an anterior to posterior shift in activation, reflecting a shift toward “non-executive” cognitive control.