Brain Architecture for an Intelligent Stream of Consciousness - Brain Theory from a Circuits and Systems Perspective - page 20

Short-Term Memory Overview
STM lasts a few seconds, and has been termed working memory because if
necessary, it could be used for second-to-second living. It stores briefly a significant
number of encoded sensations in the form of attributes, or alternately a few complex
organized images. STM is somewhat analogous to dynamic memory in a desktop
computer, which has to be constantly refreshed.
Intuitively, STM neurons differ in that they may have an internal potassium
deficit, or there may be mechanisms to inactivate their internal potassium ions [ 1 ].
Consequently a neural pulse in the dendrites can be quite long with an extended
positive peak. This pulse is maintained by an assumed lower than normal conduc-
tance from the inside to the outside ionic solution so that it cannot quickly
discharge. This may be accomplished by an insulator such as myelin. Consequently
a long pulse excites the soma to emit an extended burst of pulses easily recognized
by connecting neurons. With no extended burst the output is at rest, or false.
Long-Term Memory Overview
When conscious STM experiences images that cycle repeatedly, conditions may be
triggered to permit them to be entered automatically into LTM. Images in LTM are
not just visual pictures, but include a variety of sensory impressions, songs heard,
words read, and impressions in general that have run through STM. What is entered
automatically into LTM are particular collections of attributes that make up a
mental image.
LTM is somewhat analogous to mass memory in a desktop computer in that it
remains hidden until it is called upon. However, LTM in humans differs consider-
ably from LTM in personal computers: Human memory is associative; all images
are queried in parallel for matches to given cues. In contrast, computer memory
generally depends on knowing a numerical address, and these are looked at serially,
one at a time.
LTM and learning are two completely different things. Learning may involve
synaptic potentiation and growth over a period of time; LTM can be formed
immediately, too fast for growth, yet lasts practically forever.
For example, many of us have experienced dramatic or emotional events that
occurred quickly, but are firmly remembered. This is a salient feature of LTM; they
can be established practically immediately, and they can last indefinitely. LTM, as
the term is used in this topic, does not require synaptic growth. But it instead uses
charge mechanisms that can react immediately. These mechanisms seem to be very
different from those of STM neurons.
The exact mechanisms for LTM are still being discussed. How they work is not
obvious because neurons do not release many signals compared to solid-state
devices, making them difficult to observe in action, especially since they probably