Two papers available: V1 circuitry and multiplicative gain modulation



From: Ken Miller (ken@phy.ucsf.EDU)
Date: Mon Dec 01 2003 - 18:05:01 CET


Reprints of the following two papers are available either from
http://www.keck.ucsf.edu/~ken (Click on 'publications', then on
                               'Models of Neuronal Integration and
                                Circuitry')
or through the specific links below.

-------------------------------------------

Lauritzen, T.Z. and K.D. Miller (2003). "Different roles for simple-
and complex-cell inhibition in V1". Journal of Neuroscience 23,
10201-10213.

ftp://ftp.keck.ucsf.edu/pub/ken/lauritzen_miller03.pdf

Abstract:

Previously, we proposed a model of the circuitry underlying
simple-cell responses in cat primary visual cortex (V1) layer 4. We
argued that the ordered arrangement of lateral geniculate nucleus
inputs to a simple cell must be supplemented by a component of
feedforward inhibition that is untuned for orientation and responds to
high temporal frequencies to explain the sharp contrast-invariant
orientation tuning and low-pass temporal frequency tuning of simple
cells. The temporal tuning also requires a significant NMDA component
in geniculocortical synapses. Recent experiments have revealed cat V1
layer 4 inhibitory neurons with two distinct types of receptive fields
(RFs): complex RFs with mixed ON/OFF responses lacking in orientation
tuning, and simple RFs with normal, sharp-orientation tuning
(although, some respond to all orientations). We show that complex
inhibitory neurons can provide the inhibition needed to explain
simple-cell response properties. Given this complex cell inhibition,
antiphase or "push-pull" inhibition from tuned simple inhibitory
neurons acts to sharpen spatial frequency tuning, lower responses to
low temporal frequency stimuli, and increase the stability of cortical
activity.

---------------------------------------

Murphy, B.K. and K.D. Miller (2003). "Multiplicative Gain Changes Are
Induced by Excitation or Inhibition Alone". J. Neurosci., Nov 2003;
23: 10040 - 10051.

ftp://ftp.keck.ucsf.edu/pub/ken/murphy_miller03.pdf

Abstract:

We model the effects of excitation and inhibition on the gain of
cortical neurons. Previous theoretical work has concluded that
excitation or inhibition alone will not cause a multiplicative gain
change in the curve of firing rate versus input current. However, such
gain changes in vivo are measured in the curve of firing rate versus
stimulus parameter. We find that when this curve is considered, and
when the nonlinear relationships between stimulus parameter and input
current and between input current and firing rate in vivo are taken
into account, then simple excitation or inhibition alone can induce a
multiplicative gain change. In particular, the power-law relationship
between voltage and firing rate that is induced by neuronal noise is
critical to this result. This suggests an unexpectedly simple
mechanism that may underlie the gain modulations commonly observed in
cortex. More generally, it suggests that a smaller input will
multiplicatively modulate the gain of a larger one when both converge
on a common cortical target.

Ken
 
        Kenneth D. Miller telephone: (415) 476-8217
        Professor fax: (415) 476-4929
        Dept. of Physiology, UCSF internet: ken@phy.ucsf.edu
        513 Parnassus www: http://www.keck.ucsf.edu/~ken
        San Francisco, CA 94143-0444



 
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