Brain states

Hobson, J. A, Datta, S., Calvo, J. M. 8r Quattrochi, J. (1993). Acetylcholine as a brain state modulator triggering and long-term regulation of REM sleep. Prog. Brain Res. 98, 389-404. 

Hence an mGluR agonist and antagonist can both suppress REM sleep. This might seem incompatible with the opposing actions of these compounds on brain excitation that we have proposed. However, this apparent discrepancy can be explained by the one-stimulus model of NREM-REM sleep alternation described above. According to this model, REM sleep is a brain state of excitation or arousal that is intermediate between that of wakefulness and NREM... 

Panayiotis Tsakalis You said that what we need is to discover the reasons for human action, and not the causes of bodily movements. So, is there no common ground between reasons and causes, either ontologically or conceptually And second, you suggested that, in order to make that discovery we need to study the meaning, which depends on networks of social relations and not on brain states. Do I understand correctly what you have said Do you mean to say that mental states or brain states are totally irrelevant to the specification of meaning ... 

Is there a certain kind of anatomy that is most likely to mediate conscious activity Also, are there any kinds of anatomical arrangements that are unlikely to orchestrate the unified brain state we know of as consciousness There are likely to be important constraints governing what is suitable anatomy for underlying consciousness in contrast to what kind of anatomy is favorably suited for unconscious information processing. These constraints are important clues as to how different neurochemical circuits divide up the manifold tasks taken on by the CNS. 

Brain state-and cell type-specific firing of hippocampal interneurons in vivo. Nature 421 844-848... 

In fact, brain states are determined by so many interacting variables that it is remarkable there is as much coherence as we normally experience when passing from sleep to waking and from waking to sleep. The normality of dissociation of state components and the blurring of state boundaries are both easily understood and explained by the multidimensional AIM state space model. 

The narcolepsy story is important not only because it explains the sleep disorder itself, but because we can use it to begin to understand the normal dynamics of brain state transitions. The narcolepsy story supports the general hypothesis that state margins are fuzzy, not sharp ragged, not smooth and mushy, not crisp. State transitions need finite amounts of time to be fully accomplished. Because so many subsystems of the brain participate it is not surprising that one (or two) should lag behind (or lead) the rest. The net result is that we can be in two states at once waking and dreaming. 

The three kinds of disease process we have surveyed in this chapter are the natural analogues of experimental probes of the brain systems that normally alter brain states in animals. Not surprisingly, they alter consciousness in informative ways in humans. Strokes are the equivalent of electrolytic and excitatory neurotoxic lesions seizures are the equivalent of direct electrical and chemical stimulation alcohol is the equivalent of parenteral drug administration. In reading across the three disease classes in search of unifying concepts, I hope to stimulate a new era of experimental work in animals, as well as to celebrate what we have accomplished in the arena of human neuropsychology. 

Human sleep occurs involuntarily. That is, with rare possible exceptions, humans cannot volitionally change their brain state from wakefulness to sleep. The environment and behavior can be manipulated to increase the likelihood of sleep, but the neural activity that brings about sleep is essentially involuntary. Similarly, the maintenance of sleep (i.e., sleep length) and the termination of sleep (awakening) are endogenous processes, rather than under voluntary control. In fact, when individuals wish to impact the awakening process, they rely on external stimuli (e.g., alarm clock). In sum, endogenous neural processes control ... 

Putnam makes the same point about the identification of mental states and brain states ( Reflections , 160-161). 

Dmgs help correct an abnormal brain state... 

Arnold Mandell, the founding chairman of the Psychiatry Department at the University of California at San Diego, noted that despite much emphasis on the "visuals aroused by peyote, both Weir Mitchell and Havelock Ellis had metaphysical experiences under its influence. Ellis described a "detached yet acutely aware brain state and characterized his experience in... 

Ellis thought that peyote would never appeal to most people because it was so predominantly an intellectual experience, promoting what he called a "detached but acute brain state. Lewin called it "purely intellectual and noted many instances of "disorders of location. These observations are fascinating in themselves, but we should note that many users have been able to direct the peyote or mescaline experience into creative channels. 

This is the most radical assertion of modern dream science. Waking and dreaming are two states of consciousness, with differences that depend on chemistry. Can you digest the proposition Or does it stick in your craw Do you say, yes, but... and fill in the dots with a host of questions that are designed to express your curiosity about as-yet unexplained details, and defend yourself against the humiliation of having your dreaming reduced to a brain state You know that you are more than a brain state, don t you But how do you know that By your subjectivity, you reply (which I haven t yet explained, have I ). So you still have a loophole, but please... 

As it turned out, acetylcholine was a prime mover not only of muscles, but also of the central brain state. Acetylcholine-containing neurons fire in both waking and REM sleep, so they may help to mediate EEG activation in both states. Their excitability is apparently enhanced in REM sleep because of the decrease in inhibition from the serotonin-containing neurons, which you will remember are turned off in REM. In their variety and complexity, these neurophysiological details can become confusing. The main point to keep in mind is that in REM sleep the brain, although electrically as activated as in waking, is activated in a chemically very different way. 

Now, you might say that we have come a long way from dreaming and even from brain activation in sleep, but I don t think so and I hope that a moment s reflection will show you why. To explain why sleep normally defends us from such fates, we must assume that it is the change in brain state, with all its chemical and electrical transformations, that keeps us healthy. A second reason, admittedly theoretical, is that our drive to sleep is so intense, so demanding, and so enduring that it must have important survival functions. 

This means that, formally speaking, dreaming and severe mental illness are not only analogous but identical. This, in turn, means not only that is it easy to imagine that physical changes in brain state can produce psychosis, but also that the perfectly normal changes of sleep have very dramatic effects on our mental capacities. What s going on here ... 

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