Invasive neurophysiological correlates of human visual and motor systems
- Author(s): Niketeghad, Soroush
- Advisor(s): Pouratian, Nader
- et al.
Functional brain mapping correlates the brain anatomy and physiology to our perceptions and behaviors and allows for development of neurotherapeutic technologies. Therapeutic direct stimulation of the cortex and subcortical areas, despite its high invasiveness, remains a crucial technique for studying the neurophysiological correlates of brain networks. For example stimulation of visual cortex for restoring vision and deep brain stimulation for treatment of movement disorders provide unique opportunities to study the neural correlates of visual perception and motor behaviors. While these techniques have been around for several decades, the functional role of targeted areas and their interaction with electrical stimulation is yet to be fully understood. This work takes advantage of invasive neurosurgical techniques to refine the functional mapping of visual and motor systems. Through the application of a cortical visual prosthesis we created subject-specific retinotopic maps of the visual cortex. The functional efficacy of these maps were tested in blind subjects and was shown to restore some degree of vision allowing them to localize a static object and identify the direction of a moving target. Moreover we used intra-operative recordings from ventrolateral thalamus and sensorimotor cortex of patients with essential tremor to investigate the functional role of thalamo-cortical network in voluntary movement. By analyzing different measures of oscillatory power and connectivity, we depicted a casual mechanism in which thalamic low frequency oscillations modulate the movement-related cortical broad-band gamma activity. This understanding of visual and motor maps can advance the efficacy of visual prosthesis and deep brain stimulation therapy by highlighting the functional organization of the visual cortex and oscillatory mechanisms of thalamo-cortical interactions.