Finding high and low z cores on a data set

Hi I have a data set on a 0.5 grid, the dimension for x is 141, y is 71 and t is 38. I got the z scores and I squeeze them to get a 71*38 array. I am trying to find which years have a score below -1 and which years got a score +1. I used the following approach with no luck, the issue with this is that when I go to idx and idx1 I got only 0's and 1's with no dates. How can I get these results?

y = 1980:2017;
year = y';
year_z1 = horzcat(year,z1);



idx = year_z1(:,2) > 1;
high = year_z1(idx,:);
idx1 = year_z1(:,2) < -1;
low = year_z1(idx1,:);