I have raised this question with DUK state "glucose from carbohydrate is essential fuel for the body, especially the brain" in their Eating well with Diabetes T1 booklet
They promised to send me the references .....
I'm 72, & T2 with HBA around 6. I've been diabetic over 10 years, & low carb for 4 years. I went low carb because of muscle pain, early retina damage & chronic tiredness - & all conditions were reversed. I was in trouble with HBA=6.7. I would be foolish to eat the amount of carb recommended by DUK for both T1 & T2.
For people with Type 1 diabetes (same for T2)
The actual amount of carbohydrate that the body needs varies depending on your age, weight and activity levels, but it should make up about half of what you eat and drink over the course of a week.
I've seen the same dietitian for 10 years, & she gave me the standard advice. Partly through my experience she now has modified it, but still speaks of a minimum of 130 g carb daily. I've been invited onto the T2 X-PERT course she runs to share my experience with newly diagnosed.
I googled "glucose utilised by the brain" & found this which looks comprehensive
however it does not actually consider blood glucose measurements in relation to brain activity. Comparing a carb breakfast with a water b'fast is obviously unfair.
They also consider the effect of sugars (as distinct from slow acting carbs) & find these have a rapid action the demands & triggers insulin, with a resultant removal of blood glucose & a demand for more sugar.
I maintain a minimum level of BG of around 5 (it never falls below - during the day it rises to 7, & up to 9 after 1 1/2 hours tennis, even though I only drink water while playing - my body generates extra glucose). 5 is level of a healthy non-diabetic so should be OK for my brain function. As a T1, hypos are a danger for you, but you may find you have adequate control at present. If that is so, I think it would be unwise to increase carbs to achieve a "glucose from carb" target.
Hope that helps.