Awesome, a neuroscience forum. So glad I clicked your profile page from the Einstein forum.
Ok, I will give this a shot. And it may not be a perfect answer, but I will try. And I'm going to translate it into everyday English if I can.
The shortest answer I can think of is:
It probably means they have Attention Deficit Disorder.
Also, it's badly worded. Which part of the reticular formation, and what means of facilitation?
BUT. It might not mean that in practical terms.
What the sentence actually refers to is that the pathway that sends information from the reticular formation to the cerebral cortex isn't sending as much information as it should be, because something that should be enabling the signals is blocking it.
I don't know which pathway or which means of facilitation (likely an agonist neurotransmitter/neuromodulator/neurohormone, or a molecule that antagonises antagonising molecules [loopy, I know, but alcohol is an example].
If the RF pathway in this case is directing through the dopaminergic system, then the means of facilitation is probably noradrenaline, and the path blocked at the junction to the cerebral cortex is probably "frontal" in direction, and "GABA" in ant/agonism. A decline would be caused by not enough noradrenaline at the RF (usually due to opiates) or too much GABA elsewhere.
If the RF pathway is heading back towards the thalamocortical circuit, then it's probably part of the serotinergic system, and the decline is caused by something else. Most likely MAO.
Does that help?
It probably doesn't. Neuro is full of jargon that explains jargon.