Chemicals brain activation

Sobel N., Prabhakaran V., Hartley C., Desmond J., et al. (1999). Blind smell brain activation induced by an undetected air-borne chemical. Brain 122, 209-217. 

Most of the CNS depressants have similar actions in the brain they enhance the actions of the neurotransmitter gamma-aminobutyric acid (GABA)— neurotransmitters are brain chemicals that facilitate communication between brain cells. GABA works by decreasing brain activity. Although different classes of CNS depressants work in unique ways, it is ultimately their common ability to increase GABA activity that produces a drowsy or calming effect. 

Activation-synthesis ascribes dreaming to brain activation in sleep. The principle engine of this activation is the reticular formation of the brain stem, just as it is in waking, but the chemical mode of activation is distinctly different. It is for that reason and that reason alone that dreaming and waking consciousness are so different. In waking, the noradrenergic... 

The effects of DBS on the cortex-basal-ganglia-thalamus-cortex motor loop appear to be more complex than initially believed. The paradox of DBS is that electrical stimulation of brain tissue (which presumably induces brain activation), has a similar effect as that of a surgical lesion of that same structure (which effectively destroys brain tissue). These two realities are hard to reconcile. As indicated by [64] the ultimate elucidation of this paradox depends on the nature of the complex and interactive neural connections in the brain that communicate through electrical and chemical processes. There is an emerging view that DBS has both excitatory and inhibitory effects on how brain circuits communicate with one another depending on the distance from the electrode, the cell structures activated and the direction of the activation (ortho- versus anti-dromic). The effect appears to modulate the activity of a network as well as neural firing patterns. Long term effects on neurotransmitters and receptor systems cannot be excluded [64]. 

If dreaming is not interrupted by awakening, it is rare to have recall. Poor or no dream recall by many people is a function of the abolition of memory during these brain-activated phases of sleep. As the chemical systems that are responsible for recent memory are completely turned off when the brain is activated during sleep, it is difficult to have recall unless an awakening occurs to restore the availability of these chemicals to the brain. 

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. 

The following findings are of particular interest activation of the area of the human brain known to be an important source of the chemically distinct brain activation pattern in animal REM activation of a vast area of the limbic forebrain which is known to mediate emotion and to motivate behaviour in humans activation of the limbic areas controlling emotion, especially fear and activation of multimodal association areas of the brain. 

Binding via synchronicity occurs in milliseconds to seconds. Binding via chemical modulation occurs in minutes to hours. We need both, and we must make the best of both until we understand the mother of all questions how does the synchronous and chemically coherent activation of brain cells result in conscious experience in the first place How, after all, is the nervous system involved in subjective experience - what the philosophers call qualia - and what David Chalmers dubs the hard problem Chalmers asserts that neuroscience has not yet, and may never, solve the hard problem. If you love a mystery, and want to avoid the implications of what neuroscience is saying, you have a way out here. Neuroscientists are no more believable than anyone who waves his hands and says And then a miracle happens . The brain is a colony of neurons it thinks and therefore it is. 

Every feeling or emotion you have—in fact, all psychological experience—is based on brain activity. The fact that this physical entity, the brain, is the basis of conscious experience is the key to understanding how the chemical agents we call drugs alter psychological processes. 

Even if we do not all have firsthand experience with alcoholic beverages, we all know that their consumption slows brain activity. Ethanol, or ethyl alcohol, is the chemical in alcoholic beverages that causes this change. 

In 1890 the philosopher, William James, said that, Chemical action must of course accompany brain activity but little is known of its exact nature. The spectrophotofluo-rometer made it possible to begin to link brain chemistry and behavior. 

This last observation underscores the significance of Shulgin s contribution. The collection of chemical tools he has developed make possible the dissection of features of the human mind that can not be explored in animal studies. The physical structures of the brain, activated by phenethylamines, which support the unique features of the human psyche, may have no counterpart in non-human animals. 

A well-known radiopharmaceutical 2-fluoro-2-deoxy-D-glucose (FDG) is widely used for positron emission tomography (PET) diagnosis of brain activity. It was also evaluated as an NMR pharmaceutical for cancer detection [52]. F chemical shift images of FDG and its metabolites were obtained at 376 MHz, the mice with MH134 hepatoma having been... 

Positron emission tomography (PET) is another imaging technique that employs radioactive tracers to image brain activity. PET can detect and map the presence of glucose, neurotransmitters, and a dozen other chemicals critical to brain function. Subtle changes in brain structure or function that correlate to diseases have been used to distinguish brain chemistry changes associated with Alzheimer s disease, schizophrenia, alcoholism, anxiety disorders, and posttraumatic stress disorder. PET can also be used to detect emotional responses and perceptions of emotion. 

What Is Chemical Shift 11A Infrared Spectroscopy A Window on Brain Activity... 

Figure 10.2 Positron emission tomography (PET) scan shows normal brain activity during sleep. A radioactive isotope that emits positrons is made into a chemical compound that is absorbed by active areas of the brain. The emitted positrons collide with nearby electrons and produce gamma rays that pass through the skull to detectors surrounding the patient s head. A computer uses the detector data to construct the image.

Another clue about awareness comes from studies of brain activity with the anesthetic propofol. When this chemical saturates the brain and knocks you unconscious, all brain areas participate in a synchronized undulation. At the moment when awareness is lost, a low-frequency wave of firing neurons sweeps across the brain. Most brain areas continue to connect within their own area, but the connections between separate areas are lost. As consciousness fragments, so does the connectivity of the brain. 

Prokai, L. and Zharikova, A.D., Neuiopharmacodynamic evaluation of a centrally active thyrotropin-releasing hormone analogue [Leu ]TRH and its chemical brain-targeting system. Brain Res., 952, 268-274 (2002). 

The aroma of fmit, the taste of candy, and the texture of bread are examples of flavor perception. In each case, physical and chemical stmctures ia these foods stimulate receptors ia the nose and mouth. Impulses from these receptors are then processed iato perceptions of flavor by the brain. Attention, emotion, memory, cognition, and other brain functions combine with these perceptions to cause behavior, eg, a sense of pleasure, a memory, an idea, a fantasy, a purchase. These are psychological processes and as such have all the complexities of the human mind. Flavor characterization attempts to define what causes flavor and to determine if human response to flavor can be predicted. The ways ia which simple flavor active substances, flavorants, produce perceptions are described both ia terms of the physiology, ie, transduction, and psychophysics, ie, dose-response relationships, of flavor (1,2). Progress has been made ia understanding how perceptions of simple flavorants are processed iato hedonic behavior, ie, degree of liking, or concept formation, eg, crispy or umami (savory) (3,4). However, it is unclear how complex mixtures of flavorants are perceived or what behavior they cause. Flavor characterization involves the chemical measurement of iadividual flavorants and the use of sensory tests to determine their impact on behavior. 

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