Brain activities

Copper-64 is one of the metals used to study brain activity. Its decay constant is 0.0546 h-1. If a solution containing 5.00 mg of Cu-64 is used, how many milligrams of Cu-64 remain after eight hours ... 

True. The use of alcohol and many street drugs can lead to a slowing of brain activity and a lowering of the ability to concentrate. 

True. Cannabis is a depressant drug. One of its effects is to slow you down psychologically (slows brain activity) and, as a result, physically. 

False. Cannabis is a depressant drug which achieves its effects by slowing brain activity. This slows the user down both psychologically and physically. 

In preparation for a PET scan, a patient is injected with a dose of the tracer, which quickly accumulates in the brain. The patient is placed inside the PET scanner, and the instrument detects the gamma rays emitted by the tracer. The result is an image showing the distribution of glucose in the brain, which indicates where brain activity is greatest. 

Brain scans are used to study epiiepsy, brain tumors, strokes, Aizheimer s disease, and mentai iiiness. Each of these disorders generates a unique brain activity pattern that differs from the pattern seen in normai brains. Physicians interpret these patterns both for diagnosis and to indicate appropriate treatment. 

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. 

FIGURE 2. Panel A Elution pattern of endogenous PCP-like material from fractionated porcine brain. Activity is expressed in terms of equivalents of PCP required to inhibit 3H-PCP bindina to rat brain membranes. One unit of activity is eqivalent to 1 mole of PCP. 

The success of treatment is measured by the early termination of seizures, without adverse drug effects or brain injury. Therefore, it is essential to start pharmacologic treatment as soon as possible. First-line treatment for SE should halt seizure activity within minutes of administration. In patients who are unarous-able following treatment, an EEG should be done to rule out continued excessive electrical brain activity and confirm termination of seizures. A physical exam and evaluation of the patient s laboratory results can help determine if the cause or complications of seizure activity are being appropriately treated. 

Mathew RJ, Wilson WH, Coleman RE, Turkington TG, DeGrado TR. Marijuana intoxication and brain activation in marijuana smokers. Life Sci 1997 60 2075-2089. 

In the first of these studies, the researchers identified the areas of the brain that are associated with normal sadness. They asked volunteer subjects to think about some very sad personal experiences - and about some emotionally neutral experiences - while their brains were being imaged in a PET scanner. When thinking about the sad experiences, the volunteers reported feeling intense sadness, and many of them became tearful. The PET scans showed the changes in brain activity that accompanied these sad feelings. They demonstrated increased blood flow in the limbic system - a part of the brain that is involved in the control of emotion - and decreased blood flow in parts of the brain that are involved in the control of attention. 

In their next study, Mayberg and her colleagues scanned the brains of depressed patients who had responded positively to treatment for depression in a clinical trial of Prozac. The patients were scanned twice, once before the treatment had begun and once again after six weeks of treatment. About half of the patients responded positively to the treatment by showing at least a 50 per cent reduction in their symptoms the other half did not improve that much and were classified as non-responders. For the responders, but not for the non-responders, treatment of depression produced changes in brain activation in exactly the same areas in which normal sadness had produced changes, but in the opposite direction. In other words, successful treatment decreased brain activity in areas where sadness produces increased activity, and it increased brain activity in areas where sadness decreases it. 

Depression is not the only clinical condition in which placebo effects have been linked to changes in the brain. Changes in brain activity have also been shown in neuroimaging studies of placebo analgesics, the most influential of which was reported by a team of researchers led by Tor Wager, a neuroscientist at Columbia University who, at the time he conducted these studies, was a postgraduate student at the University of Michigan.39... 

When the placebo cream had not been applied, the researchers found activation in areas of the brain that they identified as the pain matrix . But when the same pain stimuli were administered with the placebo cream, activation in these pain-responsive regions of the brain was reduced, and the more pain relief the subjects reported, the greater the reduction of activation in the pain matrix. This told Wager that people actually do experience less pain when given placebo analgesics, and this change in experience is accompanied by changes in brain activity. 

It has now been well established that expectancies play a central role in the production of placebo effects.21 People s expectations of relief are not only correlated with how much benefit they report, but also with changes in the brain activity associated with the therapeutic benefit. These expectancies are formed and altered in many different ways. Our beliefs are influenced by parents, teachers, friends and colleagues, the advertisements we see on television and in newspapers and magazines, news programmes... 

Wada, H., Inagaki, N., Yamatodani, A. Watanabe, T. (1991). Is the histaminergic neuron system a regulatory center for whole-brain activity Trends Neurosci. 14, 415-18. 

Each sensory afferent neuron connects with an interneuron or accessory neuron. These interneurons are located entirely within the CNS, with the majority occurring in the cerebral cortex. They form numerous interconnections and are the means by which all cognitive information, thoughts and feelings, are processed. It should be emphasised that the main role of this processing of information is inhibitory. The sensory receptors provide the CNS with a massive amount of data. The interneurons process and filter this into a limited amount of useful and important informa tion. Conscious information processing forms just one part of this activity. A great deal of brain activity is concerned with routine processes, which continue without conscious awareness. 

In animal studies, high levels of cortisol have been shown to induce (increase) the activity of the enzyme tryptophan 2,3-dioxygenase in the liver, thereby decreasing the bioavailability of tryptophan to the brain. It is interesting to note that low acute doses of a number of different antidepressants inhibit the activity of this enzyme and, as a result, increase brain tryptophan concentrations, thus stimulating 5-HT synthesis (Badawy and Evans, 1982). In this way a link between the two key monoamine neurotransmitters and the hormone may be seen namely, reduced brain NA activity leads to decreased inhibition of the HPA axis, while increased levels of cortisol reduce 5-HT activity in the brain. Activation of the HPA axis has also been shown to result in tissue atrophy, in particular of the limbic system s hippocampus, and a reduction in the levels of neurotrophic factors responsible for the maintenance and optimal function of brain neurons (Manji et al., 2001). In conclusion, manipulation of the HPA axis (Nemeroff, 2002) and stimulation of neurotrophic factor activity (Manji et al., 2001) might open up new avenues for the treatment of affective disorders. 

Roland PE (1993). Brain Activation (pp. 9-83). Wiley-Liss, Chichester, UK. 

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