Focus on cognitive impairment

May 2006

The SCIT test assesses subtle forms of impairment caused by alcohol abuse, shift work, sleep deprivation and neuro-degenerative diseases such as Alzheimer's. It is also used to measure cognitive impairment in HIV sufferers and autism in children.

Participants are asked to watch as two lines of differing lengths are flashed onto a computer screen for varying periods of time. The image is flashed so quickly that participants do not register having seen it, but the image is registered by the subconscious.

This screen is followed by a mask screen -- a series of dots on a white field -- which blocks the previous image from memory. The participants are then asked to make a decision about the length of one of the lines, and the process is then repeated.

The test compares the accuracy of response to the duration that the image is on the screen. The longer the images need to be flashed on the screen for patients to produce correct responses, the higher the level of impairment.

Dr Yelland says initial tests on cognition in the elderly have found the test is the most sensitive available. "This test can determine much earlier than any other test whether cognition is affected," he says.

Dr Robinson helped develop the test because of his interest in Alzheimer's disease.

"There is currently no test that is able to pick up the first signs of impairment in ostensibly healthy people," he says.

"Once we have a cure, we have to be able to give it to people at the beginning of illness to prevent further neural damage, so if we have a test that can pick up impairment in its earliest stages, that will be very useful."