Bednar, J. A. and Miikkulainen, R. (2000b). Tilt aftereffects in a self-organizing model of the primary visual cortex. Neural Computation, 12(7):1721--1740.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... intracortically through specific long range lateral connections [7] The lateral connections have been found to link cells with similar orientation preferences [3, 7] which can allow the connections to suppress redundancy in the input and improve the cells ability to detect changes in a stimulus [2, 8, 12]. However, the role of these connections in the development and adult function of directional selectivity is not yet clear. Several computational models have shown that directional selectivity and interleaved orientation and direction maps can develop through activity dependent self organization ....

....and lateral V1 weights are adapted when the activity settles. these self organized maps and lateral connections can function in adult visual perception to segment and bind coherent objects and reduce redundancy in the input, and that visual illusions and aftereffects arise through this process [2, 4, 12]. In this paper we extend the model to develop motion and direction preferences through the self organization of spatiotemporal receptive fields. Together, these results show that activity dependent self organization can explain many of the anatomical and functional characteristics of the cortex. ....

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Bednar, J. A., and Miikkulainen, R. (2000). Tilt aftereffects in a self-organizing model of the primary visual cortex. Neural Computation, 12(7): 1721-1740.

.... connections, showing that strong lateral connections develop between neurons with similar orientation preference, and that these connections can serve as a foundation for segmentation and binding (RF SLISSOM, or Receptive Field Spiking Laterally Interconnected Synergetically Self Organizing Map; Bednar and Miikkulainen 2000b; Choe and Miikkulainen 1998; Miikkulainen et al. 1997; Sirosh 1995; Sirosh et al. 1996; Sirosh and Miikkulainen 1997) Selforganization of laterally connected maps is the first main principle of the contour integration model presented in this paper. Although patterned lateral interactions are ....

....computational power might exist to train the model with natural images as well; we expect the results to be very similar to those of the current model. However, it is interesting that such simple patterns suffice to generate contour integration at all. This result supports the previous proposal by Bednar and Miikkulainen (1998, 2000a) that internally generated patterns in the developing nervous system may pretrain the cortex before birth, explaining why a certain degree of organization and functionality already exists in a newborn cortex. Whether contour integration in the model occurs or not depends on whether the ....

Bednar, J. A., and Miikkulainen, R. (2000b). Tilt aftereffects in a self-organizing model of the primary visual cortex. Neural Computation, 12(7):1721--1740.

.... connections, showing that strong lateral connections develop between neurons with similar orientation preference, and that these connections can serve as a foundation for segmentation and binding (RF SLISSOM, or Receptive Field Spiking Laterally Interconnected Synergetically Self Organizing Map; Bednar and Miikkulainen 2000b; Choe and Miikkulainen 1998; Miikkulainen et al. 1997; Sirosh 1995; Sirosh et al. 1996; Sirosh and Miikkulainen 1997) Selforganization of laterally connected maps is the first main principle of the contour integration model presented in this paper. Although patterned lateral interactions are ....

....computational power might exist to train the model with natural images as well; we expect the results to be very similar to those of the current model. However, it is interesting that such simple patterns suffice to generate contour integration at all. This result supports the previous proposal by Bednar and Miikkulainen (1998, 2000a) that internally generated patterns in the developing nervous system may pretrain the cortex before birth, explaining why a certain degree of organization and functionality already exists in a newborn cortex. Whether contour integration in the model occurs or not depends on whether the ....

Bednar, J. A., and Miikkulainen, R. (2000b). Tilt aftereffects in a self-organizing model of the primary visual cortex. Neural Computation, 12(7):1721--1740.

.... excitatory (Grinvald et al. 1994; Hata et al. 1993; Hirsch Gilbert, 1991; Weliky et al. 1995) The model uses explicit inhibitory connections for simplicity since all inputs used are high contrast, and since it is the high contrast inputs that primarily drive adaptation in the Hebbian model (Bednar, 1997). 4 during the previous time step. The scaling factors e and i determine the relative strengths of excitatory and inhibitory lateral interactions. While the cortical response is settling, the retinal activity remains constant. The cortical activity pattern starts out diffuse and spread over ....

....direction corresponded to the orientation preference of the neuron. Perceived orientation was then measured as a vector sum over all neurons that responded to the input. In the model, the perceived orientation was found to match the absolute orientation of the input pattern to within a few degrees (Bednar, 1997). e and inhibition strength i were both 0:9. The learning rate A was gradually decreased from 0:007 to 0:0015, E from 0:002 to 0:001 and I was a constant 0:00025. The lower and upper thresholds of the sigmoid were increased from 0:1 to 0:24 and from 0:65 to 0:88, respectively. The number ....

[Article contains additional citation context not shown here]

Bednar, J. A. (1997). Tilt Aftereffects in a Self-Organizing Model of the Primary Visual Cortex. Master's thesis, Department of Computer Sciences, The University of Texas at Austin. Technical Report AI97-259.

.... neurons, the perceived orientation would thus show the direct TAE (Coltheart 1971) The fatigue theory has been discredited because it has become apparent that the adaptation is mediated by the lateral connections between neurons, rather than changes occurring within the neurons themselves (Bednar 1997; Vidyasagar 1990) The now popular inhibition theory postulates that tilt aftereffects result from changing inhibition between neurons (Tolhurst and Thompson 1975) perhaps by increases in the strength of lateral connections between them. Although the inhibition theory was first proposed in the ....

....RFLISSOM model is an iteration, i.e. a single cycle of input presentation, activity propagation, settling, and weight modification. As the number of adaptation iterations is increased, the magnitude of the TAE in the model increases monotonically, while retaining the same basic shape of figure 3 (Bednar 1997). The curve that best matches the human data was shown in figure 3. Due to the time required to obtain even a single point on the angular curve of the TAE for human subjects, complete experimental measurements of the angular function at different adaptation times are not available. However, when ....

[Article contains additional citation context not shown here]

Bednar, J. A. (1997). Tilt aftereffects in a self-organizing model of the primary visual cortex. Master's thesis, Department of Computer Sciences, The University of Texas at Austin. Technical Report AI97-259.

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Bednar, J. A. and Miikkulainen, R. (2000b). Tilt aftereffects in a self-organizing model of the primary visual cortex. Neural Computation, 12(7):1721--1740.

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