Role of Human Parietal and Premotor Cortical Areas in Complex Hand Movements

Title of Dissertation: ROLE OF HUMAN PARIETAL AND PREMOTOR CORTICAL AREAS IN COMPLEX HAND MOVEMENTS Lewis Anthony Wheaton, PhD, 2005 Dissertation directed by: Avis Cohen Department of Biology The need to understand our ability to plan and successfully execute movement is a core aspect of clinical neurophysiology. Studies in humans are particularly valuable and can have direct application to neurological disorders. While most studies have focused on the physiological characteristics of relatively simple movements (e.g., finger flexion, extension), the aim of the current studies is to determine the mechanisms involved in producing meaningful, complex movements that better represent natural movements. Electroencephalography (EEG) measures such as movement-related cortical potentials, coherence, and event-related synchronization and desynchronization allow investigators to determine the functions of specific areas and coherent networks before and during movement. Patients with ideomotor apraxia, who produce abnormal movements with spatial and/or temporal errors during pantomime of praxis movements (e.g., using a hammer, waving good-bye), were compared to normal subjects. It is our hypothesis that performance of complex movements involves early preparatory activity seen localized in the left parietal and premotor cortical areas. Additionally, we hypothesize that the activity seen in the parietal and premotor cortices is coherent and part of a functional network for such movements. Stroke patients with parietal and premotor lesions with apraxia will show a decrease in function of these areas, as well as reduced communication of the network as a result of their anatomical damage. Our studies revealed widespread and early activity of the parietal cortex for praxis movements in normal subjects. This early activity was also seen in the inferior temporal cortex. The distribution and timing of this activity was different when comparing it to simple movements, which generally had activity confined to the premotor cortex. Moreover, an active functional network was seen between the parietal and premotor cortices of the left hemisphere for praxis movements. This network differed from that seen in patients with ideomotor apraxia, where activity in the right hemisphere parietal and premotor areas became predominant. These studies provide evidence of distinct and early parietal activity before praxis and a functional network that is involved in planning and execution, which can be modified in the event of brain injury. ROLE OF HUMAN PARIETAL AND PREMOTOR CORTICAL AREAS IN COMPLEX HAND MOVEMENTS by Lewis Anthony Wheaton Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2005 Advisory Committee: Professor Avis Cohen, Chair Dr. Mark Hallett Professor John Jeka Professor Richard Payne Professor William Hodos, Dean’s Representative © Copyright by Lewis Anthony Wheaton 2005 This dissertation is dedicated to 4 special people who helped me develop my scientific curiosity at an early age; Clementine Marshall Robert Ratzlaff, PhD Richard Marconi, PhD Georgia Ann Hammond, PhD And, of course, the steadfastness of my entire loving family. My thanks to you all!