In the search for neural correlates of consciousness (NCC), the concept of 'consciousness' remains problematic. We suggest that not only the 'consciousness' in neural correlates of consciousness is a confused term, but 'correlates' is as well. When brain events are found to covary with conscious experience, these brain events can be the neural substrates of the experience, as is often...
The research of the glutamatergic system in schizophrenia has advanced with the use of non-competitive antagonists of glutamate NMDA receptors (phencyclidine, ketamine, and dizocilpine), which change both human and animal behaviour and induce schizophrenia-like manifestations. Models based on both acute and chronic administration of these substances in humans and rats show phenomenological...
Phencyclidine (PCP) can induce a model psychosis in humans that mimics the positive and negative symptoms of schizophrenia. In the social interaction test PCP induces stereotyped behaviour and social isolation in rats, and these behaviours can be inhibited by antipsychotic drugs. In order to further evaluate the predictive validity of this model of schizophrenia the anxiolytic diazepam...
A hypothesis is presented according to which structure of consciousness is quadri-dimensional. The four dimensions are duration, quality, intensity, and affectivity. One may reach this conclusion by introspection alone, or by deduction along the following steps: (1) consciousness should be examined from the point of view of evolutionary psychology; (2) this leads to the following...
While for centuries a wakeful and tranquil state or experience variously called "samadhi," "pure awareness," or "enlightenment" had been said to be a normal experience and the goal of meditation in Vedic, Buddhist, and Taoist traditions, there was little known about this behavior until recently, when the practice of "transcendental meditation" (TM) became available for study in Western...
The present studies examined the role of the spinal cord and the brain in mediating the effects of the hallucinogens N,N-dimethyltryptamine (DMT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) on the acoustic startle response in the rat. Systemic administration of these agents, which distributes to both the brain and spinal cord, produced opposite effects, as DMT depressed and 5-MeODMT...
The mode of action of indoleamine psychotomimetics has been closely linked to 5-HT. Early work showed increases in rat brain levels of 5-HT which were later localized to the nerve-ending fraction. With improved methodology, the 5-HT increment was further detected in the synaptic vesicle fraction. These effects were obtained with several indoleamine hallucinogens but not with mescaline. LSD has...
Indole and phenethylamine-type hallucinogenic drugs were studied in an FR-40 operant behavioral procedure programmed to quantify "pausing,"-a behavioral disruption somewhat specific to hallucinatory drug effects. LSD, DOM, DMT and mescaline showed a potency ratio to produce pausing that is well correlated with the hallucinatory potencies of these agents in man. Furthermore, combinations of the...
Low intravenous doses of the hallucinogen d-lysergic acid diethylamide (LSD) markedly suppress the discharge of serotonin (5-HT)-containing neurons in the dorsal raphe nucleus of the rat. Microiontophoretically applied LSD also inhibits the firing of 5-HT neurons, indicating that the inhibitory effect is mediated directing on 5-HT neurons. Forebrain neurons receiving a major serotonergic input...