Artificial Intelligence From the Bible

Memory Model

Note. This memory model is now obsolete. A revision is in the works. Please see latest news. Last revision: July 25, 2005.

Introduction

This page is where I describe a memory model of the brain which reflects my current understanding of the various metaphors and symbols found in Zechariah's vision and in the messages to the churches of Sardis and Pergamum in the book of Revelation. Please refer to the related articles for background information on this topic: Joshua the High Priest, The Lampstand, Pergamum and Sardis. Most people who read the description of the golden lampstand in Exodus 25:31-40 assume that there are seven branches altogether, three on one side, three on the other and one in the middle. But a careful examination of the text will reveal that there is no mention of seven branches anywhere. There is no mention of a middle branch either. My current understanding (which may change as I unravel these mysteries) is that there are only six branches and that they are separate and distinct from the seven lamps. The branches do not support the lamps but are attached to the two sides of the lampstand which has the seven lamps on top of it. A lamp is not a branch. I think this is rather important in deciphering the metaphorical meaning of the Branch in Zechariah's vision.

The Model

Seven Lamps and Six Branches

According to this model, memory is a signal recording and playback mechanism organized hierarchically. It consists of many short individual sequences (symbolized by a lampstand in Zechariah's vision) comprised of up to seven linked nodes each. My current understanding is that each node (symbolized by a lamp) resides in a separate layer. I use the word "node" rather than "neuron" because the function of a given node is probably performed in the brain by more than one neuron. It does not really matter for the purpose of building and intelligent machine. What matters is the principles of operation and organization.

The nodes need not be in any particular spatial or temporal order but one (depicted as node 4 in the diagram below) is different from the others. This is the master or predictor node because it the first to fire in the sequence and is used to predict when the other nodes will fire. For now, try to visualize memory as a vast, seven-layer sheet of neurons with zillions of linked sequences standing side by side, perpendicular to the surface of the sheet. In a more biologically plausible model, the predictor node layer would probably reside in the hippocampal formation of the brain.

Every sequence receives three types of input signals which are symbolized by Joshua, Joshua's friends, and Zerubbabel. The Zerubbabel signal originates straight from the sensory layers (Smyrna and Ephesus) which are called Babylon in Zechariah's text. Joshua's signal and that of his friends are generated by the simultaneous arrival of multiple signals which originate either from the sensory layers or from feedback. I will have more to say on feedback and the hierarchical organization of memory when I upload my upcoming article on the metaphor of the four chariots (Zechariah 6:1). Nodes fire under the right temporal conditions and the outgoing signals are sent to Pergamum where they are selected for motor control in the motor layer (Philadelphia).

It is important to understand that Joshua is a description of a type of input signal. The same is true of Joshua's friends and Zerubbabel. Joshua and his friends are successor signals because they normally arrive after Zerubbabel, the predecessor. The main function of the Branch signal is to anticipate the behavior of the other six nodes in the sequence. There is a single branch output coming from Joshua's node and six branch inputs going into the friends' nodes.

Notice that both the Branch and Zerubbabel pathways link the seven nodes so as to form a sequence. This is to conform with the metaphor of Zechariah 4:7-9 in which Zerubbabel is said to be the builder of the temple from beginning to end. In Zechariah 6:9-15 we read that the Branch is also involved in the building of the temple. Pay particular attention to verses 11 to 13.

Perception and the Seven Eyes

Question: What is being perceived within the context of memory sequences? Answer: intervals. The problem with recording intervals is that they can range anywhere from a fraction of a second to minutes, hours, days, weeks, months, etc... Obviously, we can neither expect nor implement the same degree of precision over the entire range of possible intervals. A proper method must be used to divide the range into manageable perceptual windows, each with its own specific precision. At first, I interpreted the metaphor of the seven eyes on one stone to mean seven perceptual windows, each having its own precision and range of intervals. The shorter the interval used in a window, the higher its precision. I have since changed my mind. The seven eyes do represent Joshua and his friends. Precision is probably handled as a smooth gradation ranging from very short intervals to very long  ones.

Attention and Awakening

As mentioned earlier, a sequence is symbolized in Zechariah's vision by a golden lampstand and each node in a sequence is represented by a lamp/eye metaphor. The idea seems to be that the lamps are lit (activated) so that the eyes (nodes) can see (receive input signals). The entire lampstand is activated at once. That is to say, all the nodes in a sequence are activated simultaneously and the activation lasts a predetermined short-term duration. The lampstand is fueled by a single bowl which is supplied with oil by the two olive branches or sons of fresh oil. The quantity of oil in the bowl symbolizes short-term memory. Lighting the seven lamps is analogous to waking up or powering up the sequence. Only a sequence which is awake can receive and send signals. Sleeping sequences do nothing. Once a sequence is awakened by the angel (i.e., is selected for input and output), it continues to run until deactivated. This is the mechanism of attention in the brain. It creates the sort of canalization of perceptual stimuli that a number of psychologists have observed in human and animal behavior: only stimuli that pertain to awakened sequences are used. The others are ignored.

Anticipation and the Branch

Looking at the figure (reproduced below), one is forced to ask, what is the purpose of the Branch signal? To answer this question, it is necessary to understand something about the timing and purpose of a sequence and the manner in which Joshua and his friends are selected. A sequence has multiple functions such as generating motor signals, but its primary purpose is to serve as a mechanism for anticipation. The idea is that the temporal behavior of the first node in the sequence (node 4 in the diagram) is enough to predict when the successor nodes will fire. By temporal behavior, I mean the interval between the arrival of Zerubbabel and Joshua and between Zerubbabel and Joshua's friends. The first interval predicts the other six intervals. An example (I wrote about it before in a news item) of where this is useful is the case of a dog chasing a hare. If the hare disappears behind a hedge, the dog will not stop. Its anticipatory mechanism will correctly predict that the hare will reappear on the other side of the hedge after a short interval. Thus the purpose of the Branch signal is to update the other six intervals every time the main node's interval is modified. The correlation between the main node interval and the others is a simple percentage. In other words, each of the six friends intervals is a fixed percentage of the main node's interval.

Intervals and Repentance

In the message to the church of Sardis we are told that the church should wake up in order to remember (record) how it received and heard, to keep it and to repent. I interpret the use of the term "how" to mean that an interval must be recorded between what is received and what is heard. It seems clear that the temporal interval between the arrival of Zerubbabel's and Joshua's signals is what is recorded. But what does "repent" mean in this context? In my opinion, it means that, once a new interval is detected (when Joshua's signal arrives), it must be used immediately to reset the intervals of all the other nodes in the sequence. This allows the succeeding nodes to fire at an anticipated preset time. The new intervals are kept until new arriving signals demand otherwise. If the sequence is asleep when new signals are received, the sequence will subsequently make wrong assumptions about changes in the environment and its behavior will be erroneous, i.e., the nodes will not fire at the correct time. In my opinion, this is the mechanism that is responsible for the psychological phenomenon known as pattern completion.

Short and Long-Term Memory

Please note that what is being memorized (recorded) is not the input connections to the nodes of a sequence but the temporal intervals between predecessor and successor signals. The input connections are learned automatically using a correlation factor which is given in the metaphor of the flying scroll. If the nodes are not already linked to form sequences, nothing can be memorized. In my understanding, the difference between short and long-term memory is simple. Short-term memory is analogous to computer RAM (random access memory). When the power is turned off, it is gone forever. Long-term memory is like EPROM (erasable programmable read-only memory). It persists after power is turned off. If a memory is short-term, it disappears (dies) immediately as soon as the sequence goes to sleep (is deactivated). But if it is long-term, it persists for a long time after the sequence is deactivated and can be recalled at any time.

In the Sardis message ( Revelation 3:2), we read "Wake up, and strengthen the things that remain, which were about to die." In order for a recorded interval to persist in the long run, it must be repeatedly strengthened. The only way to do this is to activate the nodes repeatedly or to use some other means having to do with the motivational value of the sequence. I will discuss motivation (reward and punishment) in greater detail when I update the Thyatira page in the near future.

The Magic Number Seven

Psychologists have known for some time that human short-term memory capacity hovers around the so-called magic number seven with an experimental margin of error of plus or minus two. The reason seems obvious now. Due to the organization of memory, the brain can only keep seven items in its sequence structures. It is able to scan these structures and play back the sequences in the same order in which they were recorded. This is evidenced by the fact that it is much easier to recite a random string of numbers in the same order in which they were learned than in the reverse order. Someone may point out that there can be an indefinite number of sequences activated at any given time but, as I will explain in a future article, only compatible (related) sequences can be awake simultaneously.

Sequence Learning