attached please find abstracts and preprint-locations of three manuscripts
on visual cortex modelling.
Cheers
Klaus
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Prof. Klaus Obermayer phone: 49-30-314-73442
FR2-1, NI, Informatik 49-30-314-73120
Technische Universitaet Berlin fax: 49-30-314-73121
Franklinstrasse 28/29 e-mail: oby@cs.tu-berlin.de
10587 Berlin, Germany http://ni.cs.tu-berlin.de/
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A model for the depth-dependence of receptive field size and contrast
sensitivity of cells in layer 4c of macaque striate cortex
U. Bauer^1, M. Scholz^2, J.B. Levitt^3, K. Obermayer^2, and J.S. Lund^3.
1 Technische Fakultaet, Universitaet Bielefeld,
2 FB Informatik, TU Berlin,
3 Institute of Ophthalmology, UCL
A model of LGN input to layer 4C of macaque primary visual cortex has been
used to test the hypothesis that feedforward convergence of P and M inputs
onto layer 4C spiny stellate neurons is sufficient to explain the observed
gradual change in receptive field size and contrast sensitivity with depth
in the layer. Overlap of dendrites of postsynaptic neurons between M and P
input zones proved sufficient to explain change in the lower two-thirds of
layer 4C, while more rapid change in upper 4C was matched by proposing two
different M inputs with partial overlap in upper 4C$\alpha$.
to appear in: Vision Research 1998
available at: http://ni.cs.tu-berlin.de/publications/#journals
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Influence of Recurrent Excitation and Inhibition on Receptive Field
Size and Contrast Sensitivity in Layer 4C of Macaque Striate Cortex
U.~Bauer^1, M. Scholz^3, J.B. Levitt^2, J.S. Lund^2, and K. Obermayer^3
1 Technische Fakultaet, Universitaet Bielefeld,
2 Institute of Ophthalmology, UCL,
3 FB Informatik, TU Berlin
Neurons in layer 4C in macaque striate cortex show an increase in
receptive field size and achromatic contrast sensitivity
from the bottom to the top of the layer. Using a
computational model which is based on realistic anatomical and physiological
data we demonstrate that part of the observed changes can arise from
differences in the overall balance between recurrent excitation
and lateral inhibition from two different neuron types. The model
predicts that - given the above hypotheses - lateral recurrent excitation must
come from an increasingly wider range with rise in depth of layer 4C,
and lateral inhibition must have higher threshold and gain in upper
4C$\alpha$. The anatomical substrate of recurrent
excitation are the stepped projections of spiny stellate cells. As the
possible anatomical substrate of differential inhibition
we suggest the ''clutch'' cell in lower and mid 4C and the $\alpha$-6
cell in upper 4C$\alpha$ which replaces the clutch cell as a somatic
inhibitor.
to appear in: Artificial Neural Networks -- ICANN98, 1998.
available at: http://ni.cs.tu-berlin.de/publications/#conference
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A statistical neural field approach to orientation selectivity
P. Adorján^1, G. Barna^2, P. Érdi^2, and K. Obermayer^1.
1 FB Informatik, TU Berlin
2 KFKI, Hungarian Academy of Sciences
We apply the recently proposed statistical neural field approach [Grobler
& Barna 1996, Érdi 1998] for modeling orientation selectivity in the primary
visual cortex. Firstly, we demonstrate that the neural field approach is a
powerful tool for modeling neural structures with specific lateral connections.
Secondly, we test in a biologically more plausible way our hypothesis [Bauer
et al. 1997, Adorján et al. 1998], that orientation bias and tuning in macaque
striate cortex can be generated by the same lateral interactions. The spiking
neural model shows that (i) contrast invariant tuning emerges, and (ii) the
tuning dynamics of the membrane potential and the firing rate are in accordance
with observations which until now seemed to be contradictory [Celebrini et al.
1993, Pei et al. 1994, Ringach at al. 1997].
to appear in: In Computational Neuroscience: Trends in Research 1998, 1998.
available at: http://ni.cs.tu-berlin.de/publications/#conference