Diet-induced ketosis increases capillary density without altered blood flow in rat brain.

http://www.ncbi.nlm.nih.gov/pubmed/17284577

Also we have

http://www.ncbi.nlm.nih.gov/pubmed/16594134

"These data indicate that adaptation to hypoxia did not interfere with ketosis, and that ketosis during hypoxia may lower lactate levels in brain, suggesting decreased glycolysis or increased glucose disposal."