paper available: Transfer of Coded Information from Sensory to Motor Networks

[Emilio Salinas]

FTP-host: archive.cis.ohio-state.edu
FTP-filename: /pub/neuroprose/salinas.trans.ps.Z

The following paper is available in the neuroprose archive.  It is
18 pages long; about 1 Mb compressed and about 3 Mb uncompressed.
The paper will appear in the Journal of Neuroscience.  Hardcopies 
will eventually be available but, please, only for those who are
really interested and have no means of downloading the file.  Address
questions, comments or problems to Emilio Salinas: 
emilio at eliza.cc.brandeis.edu.


                   Transfer of Coded Information 
                  from Sensory to Motor Networks
                               
                               by

                  Emilio Salinas and L.F. Abbott

                             ABSTRACT  

During sensory-guided motor tasks, information must be transferred from arrays
of neurons coding target location to motor networks that generate and control
movement.  We address two basic questions about this information transfer. 
First, what mechanisms assure that the different neural representations align
properly so that activity in the sensory network representing target location
evokes a motor response generating accurate movement toward the target? 
Coordinate transformations may be needed to put the sensory data into a
form appropriate for use by the motor system.  For example, in visually guided
reaching the location of a target relative to the body is determined by a
combination of the position of its image on the retina and the direction of
gaze.  What assures that the motor network responds to the appropriate
combination of sensory inputs corresponding to target position in
body- or arm-centered coordinates?  To answer these questions, we model a
sensory network coding target position and use it to drive a similarly
modeled motor network.  To determine the actual motor response we use
decoding methods that have been developed and verified in experimental work. 
We derive a general set of conditions on the sensory-to-motor synaptic
connections that assure a properly aligned and transformed response.  The
accuracy of the response for different numbers of coding cells is computed.
We show that development of the synaptic weights needed to generate the correct
motor response can occur spontaneously through the observation of random
movements and correlation-based synaptic modification.  No error signal or
external teaching is needed during this process.   We also discuss nonlinear
coordinate transformations and the presence of both shifting and non-shifting
receptive fields in sensory/motor systems.