Fig. 6. Evolutionary learning at the reference neuron layer.
Fig. 7. Sequence of opening of learning levels.
the copy process. Fig. 6 shows an example of the three steps given above.
In the current implementation, only one level is opened for learning at a time, while other levels
are turned off. Each level is opened for 16 learn- ing cycles. Our approach is to turn on each level
in an alternating manner until the simulation is terminated. The level opening learning sequence is
shown in Fig. 7.
3. Application problem domains
As noted earlier, this system has been applied to a number of problem domains: pathfinding
Chen and Conrad, 1994a,b, bit pattern recogni- tion Chen and Conrad, 1997a, and Chinese
character recognition Chen and Conrad, 1997b. This system was tested in the pathfinding domain
when it was first constructed. In this domain, the task was to navigate an organism, controlled by
the ANM system, to find a path from a specific location to a destination. To achieve this goal, the
organism had to learn to recognize a set of pat- terns in sequence.
Later, the system was tested in the bit pattern recognition domain. The objective was to investi-
gate the pattern categorization and generalization capabilities of the system. Different sets of bit
patterns, ranging from totally random to partially random, were used to study the influence of pat-
tern structures on the learning effectiveness.
More recently, this system was applied to Chi- nese character recognition to examine the long-
term learning capability of the system. The problem domain was defined by three training
sets: a regular Chinese character set, a stylized Chinese character set, and a random bit pattern
set. Each set had 1000 64-bit patterns. We note that the characters of the stylized set are more
similar to one another in terms of Hamming distance than those in the regular set. Due this
reason they are generally more difficult to distinguish.
In this study, the ANM system was employed to differentiate a clinical database, consisting of
1051 records. The database is further divided into two sets. The first set consisted of 676 records,
one half of which were chronic hepatitis B pa- tients, and the other half healthy non-carriers to
be referred to as the two-category set. The sec- ond set consisted of 375 records that were equally
divided into three groups: chronic hepatitis B patients, hepatitis B carriers, and healthy non-car-
riers to be referred to as the three-category set. Each of these had ten examination items that
included sex, age, and the following eight items.
Hepatitis c antibody HcAb: the appearance of hepatitis C antibodies in the blood indicates
that one might be infected with hepatitis C. Clinical reports suggest that 30 of patients
having hepatitis C might develop cirrhosis and 15 might develop liver cancer. This antibody
also suggests that those who have hepatitis C have a significant chance of being infected with
chronic hepatitis B as well.
Glutamic-pyruvic transaminase
GPT and
glutamic-oxaloacetic transaminase GOT: the GPTGOT rate is one of the major parameters
used by physicians to determine whether one is infected with chronic hepatitis B. In general,
the GPTGOT rate of a healthy person is slightly less than 1. When one has either
cirrhosis or liver cancer, the GPTGOT rate is far less than 1. On the other hand, a GPTGOT
rate greater than 1 implies that the liver is damaged.
Albumin Alb and globulin Glo: in addition to the GPTGOT rate, the AlbGlo rate is
another parameter often used by physicians to determine whether one is infected with chronic
hepatitis B. The production of Alb decreases when one is infected with chronic hepatitis B.
As to Glo, it may either increase slightly or have no significant changes at all. As a consequence,
we may conclude that one might be infected with chronic hepatitis B when the Alb
Total bilirubin TB: bilirubin is a red bile pigment found as sodium bilirubinate, or as an
insoluble calcium salt in gallstones, formed from hemoglobin during normal and abnormal
destruction of erythrocytes by the reticuloen- dothelial system. When the liver cells are dam-
aged, the process for removing bilirubins slows down. This would increase the concentration of
bilirubins in the blood, called jaundice.
Gamma-glutamylpeptidase GGT: for patients with acute hepatitis, chronic hepatitis, or cirrho-
sis, there are no significant changes in GGT. However, patients who have jaundice and liver
cancer normally have very high GGT.
In the current implementation, each of the 1051 records was transformed into a 42-bit pattern.
Each bit of a pattern corresponded to the firing activity of a receptor neuron we note that only 42
out of 64 receptor neurons are used in the current implementation, leaving 22 neurons unused. The
first bit represents the sex of each record 1, male; 0, female. The second bit represents the HcAb test
result 1, positive; 0, negative. The other 40 bits are used to represent the remaining eight parame-
ters i.e. five bits for each parameter. For each parameter, the minimal and maximal values for
these 1051 records were determined to be denoted by MIN and MAX, respectively, and the differ-
ence between these two values was divided by five to be denoted by INCR. The transformation of
each actual parameter value to be denoted by ACTUAL into the corresponding 5-bit pattern is
Á Ã
à Í
à Ã
Ä 00001,
if MIN5ACTUALBMIN+INCR
00010, if
MIN + INCR5ACTUALBMIN+INCR × 2 00100,
if MIN+INCR×25ACTUALBMIN+INCR × 3
01000, if
MIN+INCR×35ACTUALBMIN+INCR × 4 10000,
if MIN+INCR×45ACTUALBMAX
1
Glo rate decreases significantly, especially when it is far less than 1 we note that the AlbGlo
rate of a healthy person is between 1.5 and 2.5.
Alkaline phosphatase ALP: when there is con- gestion in biliary ducts, the concentration of
ALP will increase. Statistical reports show that individuals who have high hepatolithiasis and
liver cancer usually also have high ALP. The 32 two effector neurons were equally di-
vided into two groups in the two-category set. The first group of neurons represents chronic
hepatitis B patients while the second represents healthy individuals. In the three-category set, the
32 effector neurons are equally divided into four groups. The first group of neurons represents
chronic hepatitis B patients, the second represents
hepatitis B carriers, the third represents healthy non-carriers, and the fourth is unused. For each
input pattern, the first firing effector neuron is recorded. The initial effector neuron group firing
was defined as the output associated with an input pattern. When the initial effector neuron-firing
group is the same as the group determined by a physician, the system makes a correct response.
The greater the number of correct responses made by the system, the higher its fitness. The input –
output interface of the ANM system with the clinical hepatitis B database is shown in Fig. 8.
4. Experimental results
