Playpen: Delay Connection Demo
Purpose
This demo illustrates delay connections, connections
between units which are subject to a time delay. These
connections allow the network to learn about and represent
sequential processes.
In the demo, you will see how a combination of connections
with no delay and connections with a delay of one primitive
"time step" combine to yield a network in the activation of a
single unit leads to a sequence involving the activation of
successive adjacent units.
The Network
The network consists of a single layer of 4 x 4 units with
built-in connections of delay 0 and delay of one time step.
Each unit inhibits its neighbors along the non-delay connections
and excites its neighbor to the left (or, wrapping around, on
the right end of the next higher row) along the delay
connections. Phase angle is ignored for the non-delay
connections (that is, the coupling function is just 1) but taken
into account for the delay connections (the coupling function is
.5 + .5 cos x). The effect of these weights is to cause
an activated unit to activate its neighbor to the left with the
same phase angle and then
to be deactivated by it in turn. As the network repeatedly
settles, a sequence of activated units, all in phase with one
another, is activated.
What You Will See
There is only one test pattern, one in which two units
with opposite phase angles are activated (but not clamped).
When you click on "Test pattern", these two units are
activated, and the network is then permitted to settle
repeatedly as units are randomly selected and updated
80,000 times. What you will see depends on the particular
sequence in which the units happen to be selected. Most of
the time, you will see a sequence of activated units
beginning with the ones activated in the pattern and moving
to the left and upward through the 4x4 square of units.
When the unit in the left corner is activated, it then
activates the unit in the lower right corner. In each case,
the phase angle of a unit is passed onto the neighbor that
it activates along the delay connection. Sometimes,
however, one or the other unit may fade away without
activating its neighbor (though you may see recovery later
on).
Return to Playpen Technical Report 1
Michael
Gasser
Last modified: Tue Jun 24 01:25:51 EST