The results of lesions observed in all the 21 ketamine addicts were depicted in Table 2. Those who had two or less regions in the brain with lesions were classified as light damage. Those that had three to four regions in the brain with lesions were classified as moderate damage, and those with five or more regions with lesions were classified as severe damage. The MRI lesions initially were observed as hyperintense spots (holes or patches) of degeneration in the superficial white matter of the cortex which appeared as early as 1 year after ketamine addiction (Figure 1A), while each lesions spread to the internal capsule by 3 years of addiction (Figure 1B). Slightly after, patches of hyperintense degeneration spots appeared in the basal forebrain (Figure 2A), cerebellum, and pons (Figure 2B), and diencephalon at 4 years of addiction (Figure 2C).

" In this patient cohort, one patient had a combination of drugs and was taking ketamine together with amphetamine and ecstasy. He demonstrated early atrophy of cortex after taking the three drugs together in 0.5 years, in which the basal prefrontal gyrus rectus already exhibited significant atrophy (Figure 7A) when compared with control (Figure7B). Similarly, cortical atrophy also occurred early in another patient who had used a high dose of ketamine, in this case 3 g per day for 3 years (Figure 8 ). After 7 years of addiction, in all other patients, lesions then appeared in the midbrain (Figure 9). From 10 to 12 years of addiction, all lesion sites were as those described above."

Cortical atrophy was usually evident in the frontal, parietal or occipital cortices
of addicts. Such study confirmed that many brain regions in the human were susceptible
to chronic ketamine injury and presented a diffuse effect of ketamine on the brain which
might differ from other central nervous system (CNS) drugs, such as cocaine, heroin, and
methamphetamine.

A few more suggestions for those fearing that they may suffer cognitive impairment: begin exercising intellect and memory again. Rather than compulsively ingesting drugs and expecting tremendous personal insights and the ability to function as you would when not on drugs, make a conscious effort to learn. Play logic/memory games, learn new skills, hobbies, etc. There is far more to the world than simply spending all of one's time "out of body" in "the Void" (which is not to imply that such experiences may not prove valuable, or at least entertaining, for some). Take care of yourself -- eat regularly, and take a good multivitamin/multimineral. I cannot emphasize strongly enough that those suffering from cognitive impairments should avoid the use of any "recreational" drugs, including alcohol and marijuana.

https://www.erowid.org/c...ls/dxm/dxm_health2.shtml