MATLAB: reset weigths in alexnet

I would train an alexnet DNN (given by matlab function `alexnet`) from scratch (i.e. without pretraining on ImageNet given by alexnet function). I could to manually set weights but I don't know the from what distribution I can sample my initial weights. Is there a built-in matlab option that make it for me? e.g. I read that python's library has the option `pre-training=off` but I don't find a similar option in matlab.