I would like to fully understand the phase shift in the grid cell in MEC. From my understanding, since there is a hexagonal (i.e. equilateral triangle) lattice, and hence there are 3 $\phi$'s, I have the following questions in regards to that:
1). If there are 3 $\phi$'s, how does the phase shift happen in (I guess) 3 phases, i.e. why are there 3 shifts? I am just very confused at a fundamental level: why does the phase shift happen, is it because of the phase resettling in neurons?
2). As Wikipedia defines it: "Phase shift is any change that occurs in the phase of one quantity, or in the phase difference between two or more quantities", so my question is, what is the "quantity" in the example with grid cells or what is "the phase difference between two or more quantities" here?
In other words, why there is the 1st shift, the 2nd and the 3rd? Why do the second and the third happen? Is it because the pattern of grid cells is an equilateral triangle and the 1st type of signal produces the 1st grid field (the blob) and the 2nd type of signal produces the 2nd blob, here I edited this picture to illustrate my thought:
and we can see, if we model it with cosine, since