1. Introduction
Cognitive psychologists attempt to quantify the properties of short term memory (for a review
see (2)). Unfortunately this work has not led to a theoretical convergence. Various models of
memory stores have been introduced and survive in text books even though they have been
disproven(3). Presumably the lack of an accepted theory is due, in part, to a lack of connection of
the cognitive literature to the details of the underlying biochemistry. Without this “harder science”
connection it may be difficult to convince various parts of the community of the supremacy of one
theoretical model over another.
One way to make a connection from cognitive psychology to the underlying biochemistry is to
look at functional forms and see whether a particular process may decay, for example,
exponentially with a time constant that corresponds to a particular biochemical reaction. In a
recent contribution (1) the current author showed that short term memory correct recall and
recognition probabilities are linearly related to response times over a large time range (from 6 to
600 seconds). I interpreted this observation according to a new tagging model of short term
memory in which long term memory locations are tagged linearly in time. When the tagging level
is 100% the subject has identified the word. As time passes the tagging level decays. For a
subject to identify the word again the tagging level has to increase to 100% leading to a delay in
response time. The tagging level decay function is the same as for recall and recognition
probabilities and is logarithmic with time.
The current paper addresses what might be the biochemical underpinning of the tagging
model. I start by describing the tagging model and the evidence for the active tagging process
being linear in time and the subsequent tagging decay being logarithmic in time. The biochemical
process needs the same two properties: (a) an active process linear in time with (b) a logarithmic
decay time. I suggest that exocytosis, the process of depletion of presynaptic neurotransmitter
vesicles corresponds to the tagging process and endocytosis, the process of rebuilding
presynaptic neurotransmitter vesicles corresponds to the tagging level decay. A brief summary
concludes the paper.
2. The Tagging Model
The Tagging/Retagging model was introduced (1) to explain the linear relationship between
the probability of recall/recognition and response time in experiments testing recall/recognition of
words (4),(5) (see linear relationships in Figure 1, Figure 2 and Figure 3). A recent item requires