Approximately 150,000 children present each year to emergency departments (EDs) in the US with concussion and many more are treated by primary care physician, or outpatient specialists. Concussion is defined as a traumatically induced transient disturbance of brain function and involves a complex pathophysiological process. There is a variety of symptoms related to concussion, and the diagnosis of concussion requires the use of symptom-checklist. Since there is a various degree of the severity of those symptoms, the diagnosis is a subjective one and lacks sensitivity. One major problem is that approximately one-third of the children with concussion experience ongoing somatic, cognitive, and psychological or behavioral symptoms, referred to as persistent post-concussion symptoms. A recent study that investigated the validity a 12-point PPCS risk score revealed that it had modest validity (0.71). Moreover, one of the greatest concerns is the child's schedule return to activity. Since the basic mechanism for concussion is acceleration/ deceleration movement of axons, it is likely to be expressed in desynchronization of delta wave activity between anterior hemispheres as seen in pathological problems related to attention and/ or working memory). The aim of this proof-of-concept study is to find-out whether interhemispheric desynchronization of delta waves (IHDD) in the anterior hemispheres can identify acute concussion in children. If the investigators find that IHDD can accurately diagnose acute concussion, a second objective will be to examine whether this index can be a useful tool in the follow up of patients with persistent post-concussion symptoms.