A method of modulating a brain activity of a mammal is achieved by subjecting the mammal to repetitive transcranial magnetic stimulation (rTMS) with an rTMS apparatus at variable pulse intervals for a time sufficient to modulate said brain activity. Improvement in a physiological condition or a clinical condition is achieved. Conditions to be treated include but are not limited to PTSD, autism spectrum disorder and Alzheimer's disease. Wavelet transform analysis is used to determine the variable pulse intervals employed.