The Operation of Memory Systems in the Brain - Computational Neuroscience: A Comprehensive Approach - page 501

Figure 16.7
General network architecture for a one-dimensional continuous attractor model of
head direction cells which can be updated by idiothetic inputs produced by head
rotation cell firing r ID . The head direction cell firing is r HD , the continuous attractor
synaptic weights are w RC , the idiothetic synaptic weights are w ID , and the external
visual input is I V .

the same time, the idiothetic synaptic weights w ID (in which the ID refers to the fact
that they are in this case produced by idiothetic inputs, produced by cells that fire to
represent the velocity of clockwise and anticlockwise head rotation), are set up by
associating the change of head direction cell firing that has just occurred (detected
by a trace memory mechanism described below) with the current firing of the head
rotation cells r ID . For example, when the trace memory mechanism incorporated
into the idiothetic synapses w ID detects that the head direction cell firing is at a given
location (indicated by the firing r HD ) and is moving clockwise (produced by the al-
tering visual inputs I V ), and there is simultaneous clockwise head rotation cell firing,
the synapses w ID learn the association, so that when that rotation cell firing occurs
later without visual input, it takes the current head direction firing in the continuous
attractor into account, and moves the location of the head direction attractor in the
appropriate direction.
For the learning to operate, the idiothetic synapses onto head direction cell i with
fi ring r HD
i

need two inputs: the memory traced term from other head direction cells

r HD
j

(given by

r HD r HD r HD

( t + δ t )=( 1 − η ) ( t + δ t )+ η ( t ) (16.7)