Perception of objects and motions in the visual scene is one of the basic problems in the visual system. There exist 'What' and 'Where' pathways in the superior visual cortex, starting from the simple ...Perception of objects and motions in the visual scene is one of the basic problems in the visual system. There exist 'What' and 'Where' pathways in the superior visual cortex, starting from the simple cells in the primary visual cortex. The former is able to perceive objects such as forms, color, and texture, and the latter perceives 'where', for example, velocity and direction of spatial movement of objects. This paper explores brain-like computational architectures of visual information processing. We propose a visual perceptual model and computational mechanism for training the perceptual model. The compu- tational model is a three-layer network. The first layer is the input layer which is used to receive the stimuli from natural environments. The second layer is designed for representing the internal neural information. The connections between the first layer and the second layer, called the receptive fields of neurons, are self-adaptively learned based on principle of sparse neural representation. To this end, we introduce Kullback-Leibler divergence as the measure of independence between neural responses and derive the learning algorithm based on minimizing the cost function. The proposed algorithm is applied to train the basis functions, namely receptive fields, which are localized, oriented, and bandpassed. The resultant receptive fields of neurons in the second layer have the characteristics resembling that of simple cells in the primary visual cortex. Based on these basis functions, we further construct the third layer for perception of what and where in the superior visual cortex. The proposed model is able to perceive objects and their motions with a high accuracy and strong robustness against additive noise. Computer simulation results in the final section show the feasibility of the proposed perceptual model and high efficiency of the learning algorithm.展开更多
Sickle cell disease is an autosomal recessive genetic disease. Vaso occlusive crisis (VOC) is frequently seen in such patients. Painful VOC is usually recurrent, of variable severity due to many factors and its manage...Sickle cell disease is an autosomal recessive genetic disease. Vaso occlusive crisis (VOC) is frequently seen in such patients. Painful VOC is usually recurrent, of variable severity due to many factors and its management poses important challenge in the clinical practice. Few patients do not respond to standard therapies and continue to suffer severe pain for prolonged period or land to serious life threatening situation. The red cell exchange by aphaeresis is presumed to be one efficient alternative in this situation which can reduce the level of HbS below 40% - 50%. However, it is costly and not available everywhere. Both circumstances are common in our state where incidence of sickle cell disease is quite high. In such situations simple red cell exchange i.e. removing 1 unit (350 ml) of blood manually (by phlebotomy) and replacement with one unit normal red cell is effective. All of our four cases of SCA with severe acute VOC, are not responding to standard therapy but responded efficiently to this simple red cell exchange transfusion. Our present observation may pave the way of one simple, affordable, and effective measure to reduce the pain of severe acute VOC not responding to standard therapy. Moderate reduction of HbS by 8% - 14% by simple red cell exchange transfusion was associated with relief of pain of acute VOC;a new observation was reported in all our 4 cases which need to be validated by larger controlled studies.展开更多
基金the National Basic Research Program of China (Grant No. 2005CB724301)National High-Tech Research Program of China (Grant No. 2006AA01Z125)
文摘Perception of objects and motions in the visual scene is one of the basic problems in the visual system. There exist 'What' and 'Where' pathways in the superior visual cortex, starting from the simple cells in the primary visual cortex. The former is able to perceive objects such as forms, color, and texture, and the latter perceives 'where', for example, velocity and direction of spatial movement of objects. This paper explores brain-like computational architectures of visual information processing. We propose a visual perceptual model and computational mechanism for training the perceptual model. The compu- tational model is a three-layer network. The first layer is the input layer which is used to receive the stimuli from natural environments. The second layer is designed for representing the internal neural information. The connections between the first layer and the second layer, called the receptive fields of neurons, are self-adaptively learned based on principle of sparse neural representation. To this end, we introduce Kullback-Leibler divergence as the measure of independence between neural responses and derive the learning algorithm based on minimizing the cost function. The proposed algorithm is applied to train the basis functions, namely receptive fields, which are localized, oriented, and bandpassed. The resultant receptive fields of neurons in the second layer have the characteristics resembling that of simple cells in the primary visual cortex. Based on these basis functions, we further construct the third layer for perception of what and where in the superior visual cortex. The proposed model is able to perceive objects and their motions with a high accuracy and strong robustness against additive noise. Computer simulation results in the final section show the feasibility of the proposed perceptual model and high efficiency of the learning algorithm.
文摘Sickle cell disease is an autosomal recessive genetic disease. Vaso occlusive crisis (VOC) is frequently seen in such patients. Painful VOC is usually recurrent, of variable severity due to many factors and its management poses important challenge in the clinical practice. Few patients do not respond to standard therapies and continue to suffer severe pain for prolonged period or land to serious life threatening situation. The red cell exchange by aphaeresis is presumed to be one efficient alternative in this situation which can reduce the level of HbS below 40% - 50%. However, it is costly and not available everywhere. Both circumstances are common in our state where incidence of sickle cell disease is quite high. In such situations simple red cell exchange i.e. removing 1 unit (350 ml) of blood manually (by phlebotomy) and replacement with one unit normal red cell is effective. All of our four cases of SCA with severe acute VOC, are not responding to standard therapy but responded efficiently to this simple red cell exchange transfusion. Our present observation may pave the way of one simple, affordable, and effective measure to reduce the pain of severe acute VOC not responding to standard therapy. Moderate reduction of HbS by 8% - 14% by simple red cell exchange transfusion was associated with relief of pain of acute VOC;a new observation was reported in all our 4 cases which need to be validated by larger controlled studies.
