A method for testing a subject to detect a reduction in cerebral function presumably resulting from mild traumatic brain injury, that affects visual, proprioceptive, and vestibular brain functions includes: providing a user interface, input device, and portable computer into the hands of the test subject suspected of having mild traumatic brain injury; providing an icon on the user interface visible to the subject; rotating the subject holding the computer a predetermined number of revolutions, at a predetermined rate of rotation, to engage the vestibular system of the subject prior to testing; aligning, by the subject, the icon on the screen of the user interface in alignment with a test administrator; maintaining the alignment of the icon on the screen and the test administrator throughout the rotations; and conducting a real-time test for mild traumatic brain injury utilizing the user interface, the user input device, and the associated computer.