Approximately 1.1 million people a year suffer a mild traumatic brain injury (MTBI), or concussion, in the United States. Although most MTBI patients fully recover, as many as 28% have physical, cognitive, and/or emotional symptoms up to 6 months post-injury. When symptoms persist past three months, it is known as post-concussion syndrome (PCS). The cause of PCS is unknown, as structural neuroimaging and neuropsychological (NP) testing results are often normal. However, recent functional magnetic resonance imaging (fMRI) research in concussed adults showed differences in brain activity compared to controls on working memory tasks, despite normal structural MRI and neuropsychological findings. We propose improving this research by assessing brain activation patterns during simple versus complex attention and working memory tasks in 10 concussed adults via fMRI. This will be the first study to examine brain activation patterns associated with the degree of effort applied to testing, a factor known to confound interpretation of NP test performance. Validated computerized measures of selective attention (Modified Stroop Interference Task), working memory (n-back), and effort (Green's Medical Symptom Validity Test; MSVT) will be used. Ten paid controls will be used for comparative purposes. We hypothesize that concussed patients will show less brain activation than controls on complex versus simple working memory tasks and that activation patterns in concussed patients will generally be lower in those with suboptimal effort. We will also characterize self-reported emotional and physical symptoms in the PCS patients, which has not been done in prior fMRI research with this population.