Symptoms of a migraine come from specific physiologic changes that occur within the brain that cause the headache and associated symptoms of a migraine. Migraine headaches are often associated with sensitivity to light, sound, and smells. They may be preceded by an aura, a perceptual change that occurs prior to the headache. The aura may take the form of visual changes, such as partial blindness, or seeing spots or blind spots with a zigzag border. Alterations in smell or hearing can also signify an aura. Hallucinations, feelings of prickly skin, or weakness can also be signs of an aura. Auras usually occur 15-20 minutes prior to a migraine attack and are present in only 15%-20% of migraine sufferers. The head pain of migraine can be severe and debilitating. It is sometimes described as throbbing or pulsing. It is usually on one side of the head. Sensitivity to light (photophobia), sound, or smells may accompany the head pain. Nausea and vomiting are other common symptoms. Less common symptoms can include speech disturbances, numbness, and eye pain. Migraine symptoms tend to worsen with physical activity. A prodrome (group of symptoms that precedes a condition) can occur in the days prior to migraine. Symptoms of this prodrome can include depression, food cravings, yawning, neck stiffness, hyperactivity, irritability, confusion, diarrhea, or constipation.