I would be careful with mistaken short term effects from dissociative use for any sort of neurotoxicity, especially with out a physician confirming your suspicions. NMDA-antagonists use has been seen to have a effect on ones short term memory (as the NMDA receptor deals slightly with memory function). Also, I have experience slightly discombobulated speech patterns, but that go away after a break from use. I mainly notice these effects from DXM use, rather than ketamine, but I did at a time use DXM fairly frequently). I'm saying this because there are not real reports with supporting evidence that shows brain damaged from recreational use of ketamine. I mean, fuck during an event involving a lack of oxygen, the body floods the brain with glutamate (one of the bodies excitatory neurotransmitter), and when neurons are exposed to glutamate in large numbers for an extended period, brain damage ensues, however by blocking the NMDAr channels the toxicity is adverted, and minor cell damage can be repaired. Ketamine has been seen to prevent neurotoxicity resulting from the flood of glutamate or from the GABA receptors being over activated.