The purpose of this project is to employ non-invasive Functional Magnetic Resonance Imaging (fMRI) techniques in healthy human subjects to map cortical tuning properties in the control of hand movements. A fundamental question in neuroscience is how parameters of movement control are represented in the activity of neuronal populations. Tuning of neuronal populations to specific movement parameters (e.g. movement direction, velocity, force, etc.) corresponds to local information coding in the brain. Understanding tuning properties is important not only for understanding motor control, it is also essential for rehabilitating the motor impairment arising from stroke or other neurological conditions such as Parkinson's disease. Moreover, the implementation of brain-machine or brain-computer interfaces depends upon accurate decoding of cortical tuning. At present, tuning properties of cortical neurons are most often measured with invasive electrophysiological techniques; thus studies have been conducted largely in non-human primates, and constrained to relatively limited regions of the cortex. It is necessary, then, to develop techniques to measure tuning properties non-invasively, and of the whole brain, in human subjects. Preliminary studies from our laboratory demonstrate, for the first time, directional tuning of the BOLD signal in hand movements that corresponds to electrophysiological measures of tuning. The proposed studies will address three aims:
Aim 1 : To characterize global modulation of directional tuning in the cerebral cortex and cerebellum during hand movement.
Aim 2 : To characterize local modulation of directional tuning in primary motor cortex (M1).
Aim 3 : To determine the relationship between different components of the BOLD signal and directional tuning. The expected results will provide a means to non-invasively study neuronal tuning properties, and provide the foundation for future investigations in clinical populations with stroke and other neurological disorders, as well as the emerging discipline of brain-machine / brain-computer interfaces. Functional Magnetic Resonance Imaging (fMRI) is a non-invasive MRI technique that is increasingly used to measure the effectiveness of treatment for neurological injury or disorders such as stroke and Parkinson's disease. In addition, it is frequently used to plan surgical or radiosurgical treatment for brain tumors. However, the measures of treatment effectiveness are based on signal changes reflecting only changes in blood flow and oxygenation and do not reflect properties of the neurons affected by the treatment. This proposal seeks to develop fMRI methods that better reflect neuronal properties and thereby provide a quantitative means to measure response to treatment. ? ? ?
