This report on the same study above (exploring how low-carb diets may affect the brain) has a completely different take on it.
http://www.sciencedaily.com/releases/2008/12/081211112014.htm
The final quote seems to take an extreme interpretation
"The brain needs glucose for energy and diets
low in carbohydrates can be detrimental to learning, memory, and thinking."
I've put 'low' in bold because it was when the low-carb particpants' carbs were restricted to
extremely low carbohydrate intake. The study itself says:
"These data suggest that after a week of
severe carbohydrate restriction, memory performance, particularly on difficult tasks (e.g., backward compared to forward digit span; spatial memory), is impaired."
And here we see from the study that the first week mentioned above was when particpants were taken down to
0g of carbs.
"Individuals who selected the LC diet received instructions to reduce their daily carbohydrate intake to 0 g for 1 week. For the second week, they could add between 5 and 8 g of carbohydrates per day. For the third week, they could add an additional 5–8 g per day (total 10–16 g per day)."
Just one small example here but it shows how things can be poorly interpreted.