one of the CA3 is sensory

sensory input stimulate S one of CA3 units


[Sensor input]
"Sensory module stimulates the CA3 unit S that represents the current location (or the currently perceived context) on the cognitive map."
=> Number of CA3 units should be number of grid


By assumption, the goal module can be gtunedh to a CA1 unit G that represents the location of the current goal.


[Motor]
rat moves following the equation

x(t+1) = x(t)+ \alpha v_x(t) + a_x(t)
y(t+1) = y(t)+ \alpha v_y(t) + a_x(t)

(x(t), y(t)) is the location of the lat; (v_x(t), v_y(t)) is the speed and (a_x(t), a_y(t)) is the Gaussian random variable implying rat's acceleration which has a zero mean and a standard deviation \sigma

Author take the value \alpha= 0.875 and \sigma^2 = 0.5 v is reset to zero at each bump into a wall.


By assumption, the goal module can be gtunedh to a CA1 unit G that represents the location of the current goal. If, in addition, the goal module is modulated by the theta rhythm, it may be able to detect a moment of time of the strongest PP effect on G activity.

In this case, the control module may be able to detect the momentary PP direction in CA3 that produces the strongest effects on G. For example, the control module may receive information from CA3 about spontaneous fluctuations of the PP direction. Based on this combined information about the momentary PP direction and the moment of G's strongest response to theta, the control module selects the next move and sends a command to motor module, which controls the motion of the model animal in its environment.



It consists of oscillations of the phase of place-cell firing with respect to the theta rhythm. According to a common description of this phenomenon (Skaggs et al. 1996), the firing phase of a place cell gradually changes from late to
early phases of the hippocampal 
 rhythm, as the rat traverses the
place field of the given cell. An alternative, equivalent description
of the same phenomenon can be given in terms of a population
code (Samsonovich and McNaughton 1997). In short, one
can imagine positioning all hippocampal place cells in the environment,
each at the maximum of its own firing rate distribution.
Over such an abstract construct (called a chart), the plot of
a momentary smooth distribution of place-cell activity would
result in a bell-shaped function (the activity packet) (Fig. 1 in
Samsonovich and McNaughton 1997), which oscillates with the

 rhythm in the direction of the animalfs head (Fig. 1D,E). These
oscillations constitute PP.