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Event descriptions.
An event is a description like
event(evkey,[sp1,obj1,obj2,obj3,goal1,wgoal1,cec1,pcec1])
which a more or less fixed structure, which
can be stored in the hippocampal store.
The square brackets indicate a fixed number of slots
rather than a list of variable length.
Each component is a change received from some cortical
module; usually only one, or a few, of these have changed.
evkey is the event characterization, or key, which will
be constructed by the hippocampal complex. It is a brief summary
of the event, which
includes the important features that
change, maybe one or two very important features, and maybe
any novel features or changes.
Episodes.
For a sequence of events within one governing context,
the system forms an episode representation as a sequence of events.
Our idea, taken from the work of Wickelgren,
is that the size of this sequence is limited to
a small number, such as 3, 4 or 5, of events. In this case,
it doesn't matter much whether we think of events
as having ``next'' or ``prior'' relations, or whether
we think of the episode as having a small number of slots
containing event representations.
This is an expression,
of the form episode(epkey,[evkey1,evkey2,evkey3,evkey4]),
where epkey is the key of the episode.
epkey is a relatively unique description of the episode,
which is a summary expression which
characterizes the event, and which will also serve to allow
it to be accessed in associative memory.
It is of bounded size
and certainly much smaller than the full description
of the event. Episodes can also be composed of other episodes:
episode(epkey,[epkey1,epkey2,epkey3,epkey4]).
We will assume that the associative store provides access
by relative association, by which we mean that there is
an existing currently retrieved item and then the key will
find an item stored relative to it. We can represent
this in our formalism by giving the complete global key,
but in more realistic implementations, only the local key would be needed.
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