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We describe a model of visual processing in which feedback connections from a higher- to a lower-order visual cortical area carry predictions of lower-level neural activities, whereas the feedforward connections carry the residual errors between the predictions and the actual lower-level activities. When exposed to natural images, a hierarchical network of(More)
To describe phenomena that occur at different time scales, computational models of the brain must incorporate different levels of abstraction. At time scales of approximately 1/3 of a second, orienting movements of the body play a crucial role in cognition and form a useful computational level--more abstract than that used to capture natural phenomena but(More)
Neurons in the mammalian primary visual cortex are known to possess spatially localized, oriented receptive fields. It has previously been suggested that these distinctive properties may reflect an efficient image encoding strategy based on maximizing the sparseness of the distribution of output neuronal activities or alternately, extracting the independent(More)
In this paper, we evaluate performance of a real-world image processing application that uses a cross-correlation algorithm to compare a given image with a reference one. We implement this algorithm on a nVidia GTX 285 GPU using CUDA, and also parallelize it for the Intel Xeon (Nehalem) and IBM Power7 processors, using both manual and automatic techniques.(More)
The early visual cortices represent information of several stimulus attributes, such as orientation and color. To understand the coding mechanisms of these attributes in the brain, and the functional organization of the early visual cortices, it is necessary to determine whether different attributes are represented by different compartments within each(More)
We studied the effects of prenatal cocaine and morphine given separately and in combination on the (1) postnatal brain mu-opioid receptor development and (2) interaction of dopamine with mu receptors. Pregnant rats received single daily intraperitoneal (I.P.) injections of saline, cocaine (20 mg/kg), morphine (2 mg/kg), or the combination of both drugs from(More)
nimal brains form the centrepiece of nature's development of information-processing machines. In attributes such as adaptability and fault tolerance they are likely to remain unsurpassed by any human-built machine in the foreseeable future. Digital computers form the centrepiece of the past quarter-century's explosion in information technology. In terms of(More)
LIMITED DISTRIBUTION NOTICE: This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be(More)
X-ray luminescence computed tomography (XLCT) is proposed as a new dual molecular/anatomical imaging modality. XLCT is based on the selective excitation and optical detection of x-ray-excitable nanoparticles. As a proof of concept, we built a prototype XLCT system and imaged near-IR-emitting Gd(2)O(2)S:Eu phosphors in various phantoms. Imaging in an(More)
Pregnant rats received daily injections of saline, cocaine (20 mg/kg), morphine (2 mg/kg), or the combination of both drugs, on days 13-20 of gestation. Cyclin-dependent kinase 5 (Cdk5) activity was then measured in the resulting pups on postnatal days 1, 7, 14 and 28. Cocaine resulted in a time dependent increase in brain Cdk5 activity which peaked on day(More)