Hi Tedmich, can you please link to the original MIT article?
I´m all for experimenting but since in this case it involves your loved and irreplaceabe Dad I´d be very vary cautious, in any case check with is Doctor or Neurologist first.
Flashing lights can and do have a strong effect on human mind, I speak from personal experience because I designed and sold "Disco Light" flash units, the first ones in Argentina ... designed and made from scratch just based on a Newspaper report about NY Studio 54, go figure.
Among many other things, experimented a lot on supplies, triggers, frequencies, flash tube overheating, etc. and quickly found that certain frequencies had a powerdul effect.
Some were very annoying and unbearable, others were "hypnotical", I set the speed pot to that particular frequency and "couldn´t let go" and/or lost some perception on what was around, fully focusing on the blinking lamp.
Not personal but read on "serious" sources talked about seizures caused on epileptic people at certain frequencies.
That said, given eye slow/integrating response to light pulses, which happens in the eye itself light detector , which is chemical and depends on certain photochemical reactions happening, even before being sent along a nerve , and way before brain processing, makes me think that brain will receive 40 Hz light like continuous light plus a little ripple.
In my experiments the psychoactive frequencies were WAY lower, on the order of 1 to, say, 5 Hz.
There is one frequency, which I *guess* matches the eye cell ON/OFF time constants which is mind boggling.
I guess light intensity also plays a role: I bet that a couple blinking Leds at that frequency won´t do too much, but a powerful flash tube wipes everything else out ... even if less than a millisecond wide.