COMPuter-assisted Self-training to Improve EXecutive Function

This study is testing a computer-based brain training program designed to help people who have had a stroke, cardiac arrest, or Parkinson's disease and are experiencing memory or thinking (executive function) difficulties. The training is done at home via computer. **You may be eligible if...** - You are 18 or older - You have had a stroke (within the last 6 months), cardiac arrest (within the last 6 months), or have a diagnosis of Parkinson's disease - You are experiencing working memory difficulties (scoring 5 symbols or fewer on a specific memory test) - You have a computer and internet access at home - You are able to provide informed consent **You may NOT be eligible if...** - You have another neurological or psychiatric condition that would interfere with participation - For stroke patients: you have severe denial of cognitive symptoms or severe speech/language problems that make testing unreliable - You are not willing or able to participate according to the investigator's judgment Talk to your doctor to see if this trial is right for you.