You can use the function normalize and specify which dimension you want to normalize.
From the documentation
"N = normalize(A) returns the vectorwise z-score of the data in A with center 0 and standard deviation 1.
If A is a vector, then normalize operates on the entire vector.
If A is a matrix, table, or timetable, then normalize operates on each column of data separately.
If A is a multidimensional array, then normalize operates along the first array dimension whose size does not equal 1. "