![](https://csdnimg.cn/release/download_crawler_static/9434498/bg5.jpg)
390
F.
ROSENBLATT
respond
in
much
the
same
fashion
as
the
A-units. Each response
has a
typically large number
of
origin points
located
at
random
in the
An
set.
The
set of
A-units transmitting impulses
to a
particular response
will
be
called
the
source-set
for
that
response.
(The source-set
of a
response
is
iden-
tical
to its set of
origin points
in the
A-system.)
The
arrows
in
Fig.
1
indicate
the
direction
of
transmission
through
the
network. Note
that
up
to An all
connections
are
forward,
and
there
is no
feedback. When
we
come
to the
last
set of
connections, between
An
and the
R-units, connections
are
established
in
both directions.
The
rule
governing feedback connections,
in
most models
of the
perceptron,
can
be
either
of the
following
alternatives:
(a)
Each response
has
excitatory
feedback
connections
to the
cells
in its
own
source-set,
or
(&)
Each response
has
inhibitory
feedback
connections
to the
comple-
ment
of its own
source-set
(i.e.,
it
tends
to
prohibit
activity
in any
association
cells
which
do not
transmit
to
it).
The first of
these rules seems more
plausible
anatomically, since
the R-
units might
be
located
in the
same
cortical area
as
their respective source-
flHOKfflt
LIHCt
>W
IHHtllTOMV
COHKECTIOHI
FIG.
2A.
Schematic representation
of
connections
in a
simple perceptron.
OWHWTMV
OMNICTIOH
•
EMITITMV
CONNtcriON
FIG.
2B.
Venn diagram
of the
same per-
ceptronf
(shading shows active
sets
for
RI
response).
sets,
making mutual excitation
be-
tween
the
R-units
and the
A-units
of
the
appropriate source-set highly
probable.
The
alternative rule
(6)
leads
to a
more readily analyzed sys-
tem, however,
and
will
therefore
be
assumed
for
most
of the
systems
to be
evaluated here.
Figure
2
shows
the
organization
of
a
simplified
perceptron, which
affords
a
convenient entry into
the
theory
of
statistical
separability.
After
the
theory
has
been developed
for
this
simplified
model,
we
will
be in a
better
position
to
discuss
the
advantages
of
the
system
in
Fig.
1. The
feedback
connections shown
in
Fig.
2 are in-
hibitory,
and go to the
complement
of
the
source-set
for the
response
from
which
they originate; consequently,
this system
is
organized according
to
Rule
b,
above.
The
system shown
here
has
only three stages,
the first
association
stage
having been elim-
inated.
Each
A-unit
has a set of
randomly
located origin points
in the
retina. Such
a
system
will
form
simi-
larity concepts
on the
basis
of
coin-
cident
areas
of
stimuli, rather than
by
the
similarity
of
contours
or
outlines.
While
such
a
system
is at a
disadvan-
tage
in
many discrimination experi-
ments,
its
capability
is
still quite
impressive,
as
will
be
demonstrated
presently.
The
system shown
in
Fig.
2
has
only
two
responses,
but
there
is
clearly
no
limit
on the
number
that
might
be
included.
The
responses
in a
system organized
in
this
fashion
are
mutually exclusive.
If
RI
occurs,
it
will
tend
to
inhibit
Rs,
and
will
also inhibit
the
source-set
for
R
2
.
Likewise,
if
Ra
should occur,
it
will
tend
to
inhibit
RI.
If the
total
impulse
received
from
all the
A-units
in
one
source-set
is
stronger
or
more
frequent
than
the
impulse received
by the
alternative (antagonistic)
re-
sponse, then
the first
response
will