Dessyedee. Critical Flicker Fusion was used a lot in medicines research in the 80's and 90's. It's main advocate was Ian Hindmarch at the University of Leeds and more recently Keith Wesnes in his battery of computerised cognitive tests.  I suggest you Google their names and you should get a lot of references. I am fairly sure that Keith has developed it for clinical use.  It is very sensitive, even to levels of arousal in the circadian rhythm.  Good hunting.  Andrew.

Thank you. I will follow up on these contacts. I have an idea for a portable system but don't want to reinvent the wheel, so to speak.

Good luck Dessyedee.  I always liked CFF because it is a really a sensitive measure of arousal or alertness; but I 'm not sure that it would detect impaired cognitive function per se.  it is so sensitive that it can track  circadian rhythms, so if you do use it in trials or clinics it may be necessary to keep to the same or similar times of day.  In the 80-90s it was used mainly to detect sedation and time to complete removal of sedation because the new GABA agonist drugs like zolpidem claimed reduced hangovers the morning after.  Faster recoveries from IV anaesthetics like Althesin/alphaxolone were based on CFF data.  New antihistamines were aimed at avoiding the sedation of some phenothiazines.  Hindmarch combined it with reaction times as a measure of fitness to drive cars for example. 

Having said all that, it is quite possible the CFF would track losses of cognitive function if the impaired cognitive ability was mirrored by inability to react to the flickering light. CFF is so practical and inexpensive that the idea certainly merits a study to find out if CFF and MCI tests do correlate.  That would be your first step anyway. 

Thanks again. I'm hunting. My original PhD thesis included the use of 4 choice reaction time program on a Psion pocket computer to determine correlations with low and high blood glucose levels. I just heard (somewhere, radio?) about an "app" for smart phones that I believe might use CFF as the foundation concept on the app.  Now I'm interested to track this down. I was going to build my own CFF tool using Arduino technology, but if there is already an 'app' out in the public domain, it would be useful to study this for validity etc.  My interest is primarily in providing patients with self-monitoring (biofeedback) type tools to help them with self-care decision making.  However, since I prescribe medications and worry about impaired driving a LOT, the CFF on a smart phone (or Fit-bit type device) would be useful for my patient care. My interest is in empowering the patient to be alerted to MCI through natural setting and inexpensive methods.  My late husband was a pilot. He used to toss a coin in the air while flying at high altitude. When he couldn't catch the coin and toss it easily, he new he needed to get down to lower strata where there was more oxygen.