One type of biofeedback called " neurofeedback", provides immediate feedback about brain activity and helps to strengthen healthy brain function via operant conditioning. Electrical activity from the brain is collected via sensors placed on the scalp using electroencephalography (EEG), with feedback presented using video displays or sound. Many mental disorders have been treated with neurofeedback, including ADD/ADHD, panic attacks, learning disorders, social problems, anxiety, depression, PTSD and migraines. There is now substantial evidence to support this treatment. NFB is non-invasive and there are no drugs involved. The multi-session approach usually takes about one month or so. The majority of neurofeedback clients see lasting and positive results. Many times these results are remarkable, even when other treatments fail.