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2000 (1)
1998 (1)
1Author    PieterR. RoelfsemaRequires cookie*
 Title    Solutions for the Binding Problem  
 Abstract    Visual cortical neurons are broadly tuned to one or a few feature dimensions, like color and motion. This is advantageous because broadly tuned neurons can contribute to the repre­ sentation of many visual scenes. However, if there are multiple objects in a visual scene, the cortex is at risk to combine features of different objects as if they belong to a single object. The term "binding problem" was introduced to refer to the difficulties that may occur in sorting out those responses that are evoked by a single perceptual object. The present article reviews proposals suggesting that the binding problem is solved by labelling an assembly of neurons that is responsive to a single perceptual obejct. Evidence is reviewed in favor of two possible assembly-labels: rate enhancement due to visual attention and neuronal synchrony. Assembly-labels should be spread through the cortical network to all neurons that have to participate in an assembly The present article tries to shed light on the mechanisms that subserve such a selective spread of assembly labels. Moreover, it is suggested that assembly labels may fulfill an equivalent role in the motor system, since binding problems can also occur during the generation of useful patterns of motor activity. 
  Reference    Z. Naturforsch. 53c, 691 (1998); received May 5 1998 
  Published    1998 
  Keywords    Visual Attention, Neuronal Synchrony, Cell Assemblies, Visual Cortex, Motor Cortex 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0691.pdf 
 Identifier    ZNC-1998-53c-0691 
 Volume    53 
2Author    Christoph Bauer3, Thomas Burger3, Martin Stetterb, ElmarW. Lang3Requires cookie*
 Title    A Neural Network Model for the Self-Organization of Cortical Grating Cells  
 Abstract    A neural network model with incremental Hebbian learning of afferent and lateral synap­ tic couplings is proposed,which simulates the activity-dependent self-organization o f grating cells in upper layers of striate cortex. These cells, found in areas VI and V2 of the visual cortex of monkeys, respond vigorously and exclusively to bar gratings of a preferred orienta­ tion and periodicity. R esponse behavior to varying contrast and to an increasing number of bars in the grating show threshold and saturation effects. Their location with respect to the underlying orientation map and their nonlinear response behavior are investigated. The number of emerging grating cells is controlled in the model by the range and strength of the lateral coupling structure. 
  Reference    Z. Naturforsch. 55c, 282 (2000); received July 5/Decem ber 10 1999 
  Published    2000 
  Keywords    Self-Organization, Nonlinearities, Visual Cortex, (Anti-)H ebbian Learning, Lateral Plasticity 
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 TEI-XML for    default:Reihe_C/55/ZNC-2000-55c-0282.pdf 
 Identifier    ZNC-2000-55c-0282 
 Volume    55