Neuroimaging techniques have been extensively used to map functional organizations of cortical areas in the human brain. However, limitations of detection sensitivity, spatial resolution, and the depth of imaging penetration make most existing techniques unsuitable to detect the activation in small subcortical nuclei located in the thalamus. As such, subcortical nuclei are parts of the neural network in the human brain and play a very important role in many functions. Thus, they provide challenging targets for functional mapping of a large-scale neural network with neuroimaging techniques. Recently, the functional magnetic resonance imaging (fMRI) technique based on blood oxygen level dependent (BOLD) contrast has become one of the most useful neuroimaging techniques in terms of sensitivity and spatial specificity. We have demonstrated the feasibility of using fMRI for detecting the activation in the small lateral geniculate nuclei (LGN) in the thalamus during visual stimulation. The long-term objective of this project is to explore and improve the capability of high-resolution fMRI for mapping functional organizations and sub-organizations covering both cortical and sub-cortical gray matters, consequently, to achieve functional mapping of thalamocortical networks in the human brain. This goal will be accomplished by the specific aims: (1) to develop and improve high-resolution fMRI and anatomical MRI techniques for reliable mapping of functional activation in small nuclei in the thalamus together with cortical activation; (2) to evaluate the spatial specificity, detection sensitivity and reproducibility of fMRI mapping of subcortical neuclei in single subjects; (3) to examine the capability of using high-resolution fMRI at high magnetic fields for mapping functional sub-organizations in the LGN during visual perception; (4) to determine the functional correlation between the LGN and V1 related to different visual perception processing; and (5) to study and demonstrate thalamocortical networks involving cognitive visual processing in the human brain using high- resolution fMRI. The results from these experiments will: (i) establish a methodology using fMRI for functional mapping of neural networks encompassing both cortical and subcortical gray matters in the human brain and (ii) demonstrate the capability of fMRI for determining complex neural networks involving visual perception and cognitive visual processing. This work will fill a gap between neuroimaging techniques and functional mapping of the thalamocortical networks. This is vital to the understanding of human brain functions involving both sensory perception and higher cognitive processes at physiological and pathological conditions.
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