Psychiatry and Clinical Neurosciences
June 19, 2019
Kenji Hashimoto
325 citations
Ketamine, particularly its enantiomers (R)-ketamine and (S)-ketamine, shows rapid and sustained antidepressant effects in patients with treatment-resistant major depressive disorder (MDD) or bipolar disorder (BD). While (S)-ketamine (esketamine) was FDA-approved as a nasal spray in 2019 due to its higher affinity for the NMDA receptor, preclinical data suggest (R)-ketamine may have greater potency, longer-lasting effects, and fewer side effects. The author reviews the historical development of ketamine enantiomers and their metabolites, compares other rapid-acting antidepressant candidates, and discusses the molecular and cellular mechanisms underlying ketamine's effects.
Psychiatry and Clinical Neurosciences
December 1, 1966
Akira Kasamatsu, T Hirai
324 citations
During Zen meditation, EEG recordings from 48 Zen priests and disciples showed a consistent pattern of brainwave changes: alpha waves appeared within 50 seconds of starting meditation, their amplitude increased, and their frequency decreased over time. In some priests, rhythmic theta trains emerged. These four EEG stages corresponded to the disciples' mental states, as evaluated by a Zen master, and to their years of training. Unlike drowsiness or hypnotic sleep, the meditation EEG pattern was more persistent and did not shift into deeper sleep. Alpha blocking in response to repeated click stimuli showed no habituation during meditation, whereas control subjects habituated quickly. These findings indicate a specific change of consciousness during Zen meditation.
Psychiatry and Clinical Neurosciences
April 1, 2008
Miho Miyajima, Toshihiko Matsumoto, Shigeo Ito
45 citations
A 40-year-old man with no prior mental illness was brought to an emergency room in a delusional, psychotic state after ingesting a liquid labeled 'Vanilla aroma' to enhance sexual pleasure. The substance contained 2C-T-4, a phenethylamine analog hallucinogen not detected by standard urine screening. He recovered with neuroleptic medication within 17 hours. This is the first reported clinical case of acute psychosis caused by 2C-T-4, which is not legally controlled in many countries including Japan and the USA, and is difficult to detect on routine drug screens.
Psychiatry and Clinical Neurosciences
December 1, 1994
38 citations
During Zen meditation (Zazen), slow alpha brain waves appeared in most subjects regardless of meditation experience, but theta waves appeared only in monks (priests and disciples), predominantly in the frontal region. The frequency of theta waves increased with more years of Zen training. In experienced monks, theta 2–3 (6.0–8.0 Hz) waves increased while the increase in alpha 2 (9.0–10.0 Hz) waves was attenuated over the course of meditation. These EEG changes may reflect a mental state of relaxation combined with heightened consciousness induced by Zazen.
Psychiatry and Clinical Neurosciences
October 1, 2024
Shakila Meshkat, Fatemeh Gholaminezhad, Eric Vermetten et al.
24 citations
A systematic review of 20 studies with 2,959 participants found that psilocybin's effects on cognitive function are mixed. Global cognitive function and processing speed remained mostly unchanged in healthy individuals, while improvements in sustained attention, working memory, and executive function were reported in patients with treatment-resistant depression. Emotional processing and empathy were positively modified, especially in these patients, but cognitive empathy and social cognition were not significantly altered. Cognitive flexibility and creative cognition initially declined but could improve over time. Psilocybin improved semantic associations and associative learning, but effects on episodic and verbal memory were less pronounced than with other cognitive enhancers.
Psychiatry and Clinical Neurosciences
June 1, 1967
Y Shimazono, Katsumi Ando, Takashi Tanaka et al.
4 citations
In 45 normal subjects, horizontal eye movements changed after psychotropic drugs. Amobarbital and chlorpromazine gradually eliminated rapid eye movements. LSD-25 increased rapid movements in 80% of subjects and produced large, slow pendular movements in about half, especially among those showing euphoria, disinhibition, and ecstasy. Psilocybin caused similar pendular movements but with longer duration. Methamphetamine and epinephrine initially decreased slow movements and increased rapid ones; epinephrine later transiently increased slow movements. The findings suggest different drugs distinctly alter eye movement patterns, possibly reflecting their mechanisms of action.
Psychiatry and Clinical Neurosciences
February 26, 2026
Kengo Yonezawa, M. Hirata, Hiroaki Takano et al.
1 citation
Psilocybin, a classic psychedelic compound, is being reexamined as a treatment for psychiatric disorders after decades of legal restrictions. Clinical trials report therapeutic effects for major depressive disorder, depressive symptoms in life-threatening illnesses, and some substance use disorders, with phase III trials for depression underway. Short-term side effects are generally mild and transient, but long-term effects need investigation. Neuroimaging research, mainly using MRI and EEG, is limited and focused on MDD, though ongoing trials include broader studies. Regulatory frameworks vary; controlled use is permitted in Switzerland, parts of the US, Canada, and Australia. Challenges remain, including the need for larger blinded trials and standardized protocols.