Subject Recruitment and Experimental Approach. Based on the frequency of migraine attacks per month, Low frequency (LF) and High frequency (HF) episodic migraine patients were recruited to the study. During the study visit Quantitative Sensory Testing (QST) for pain threshold was performed for each subject and questionnaires were filled out. For each subject morphological (as part of the anatomical scan) and functional (evoked to thermal stimuli) images were acquired as shown in the diagram. Thermal stimuli paradigm is also shown in the diagram.