People take drugs for many reasons. They can produce a so called rush of pleasurable sensations, which is a dramatic and memorable experience. Sometimes drugs are taken because of peer pressure or stress. Related to the latter, drugs are sometimes used to self-medicate unpleasant feelings such as pain, anxiety, or depression. When addicted, users may take drugs to avoid the negative symptoms of withdrawal. Withdrawal is a series of distressing feelings and physiologic reactions that occur when drug taking is stopped. Drugs effects to our Brain Different parts of the human brain have different functions. Seventy-five percent of the human brain is made up of the wrinkled outer covering referred to as the cerebral cortex, which has different functional areas. Strokes or lesions of the motor cortex result in paralysis, the extent of which is dependent on the extent of the motor area involved. Patients with strokes in the association cortex have deficits of perception and attention. When the temporal lobe is damaged, the ability to recognize or name objects is impaired. Lesions or strokes of the frontal lobe result in personality changes, planning deficits, and inabilities to carry out complex behaviors.