Brain regions frontal cortex

Figure 8.3 Brain areas receiving a prominent noradrenergic innervation. Most brain regions are innervated by neurons projecting from both the locus coeruleus and the lateral tegmental system. However, the frontal cortex, hippocampus and olfactory bulb are innervated exclusively by neurons with cell bodies in the locus coeruleus. With the exception of the paraventricular nucleus (and possibly the suprachiasmatic nucleus) hypothalamic nuclei are innervated by neurons projecting from the lateral tegmental system...

Figure 8.11 Noradrenaline efflux, measured by microdialysis, in the rat frontal cortex and hypothalamus, (a) Repeated exposure to a tone, alone, has no effect on noradrenaline efflux in either brain region, (b) After repeated pairing of the tone with transfer of the rat to a brightly lit (aversive) arena, the sound of the tone alone triggers a significant ( P<0.05, cf last basal sample) increase in noradrenaline efflux in the frontal cortex, but not the hypothalamus. (Based on a figure from McQuade and Stanford 2000)...

Figure 7.8 Long-term effects of MDMA on tissue levels of 5-HT (left panel) and DA (right panel) in brain regions. Male rats received three i.p. injections of 1.5 or 7.5 mg/kg MDMA, one dose every 2 h. Saline was administered on the same schedule. Rats were killed 2 weeks after injections, brain regions were dissected, and tissue 5-HT and DA were assayed by HPLC-ECD.112 Data are mean SEM expressed as percent of saline-treated control values for each region, N = 5 rats/group. Control values of 5-HT and DA were 557 24 and 28 4 pg/mg tissue for frontal cortex (CTX), 429 36 and 10,755 780 pg/mg tissue for striatum (STR), and 1174 114 and 4545 426 pg/mg tissue for olfactory tubercle (OT). Significant compared to saline-injected control for each region (P < 0.05 Duncan s).

Textbooks on neuroscience often describe the location and function of hundreds of individual brain regions (see references above). However, for current purposes these will be kept to a minimum (Figure 2.1). Anatomically, the brain can be subdivided into the forebrain containing the telencephalon and diencephalon, the midbrain or mesencephalon and the hindbrain (metencephalon and myelencephalon). The telencephalon includes the left and right cerebral hemispheres encompassed by the cerebral cortex (neocortex). Cortex is a translation of the word bark and is so-called because its surface, made up of numerous sulci (grooves or invaginations) and gyri (raised areas), is on the outer surface of the brain like the bark of a tree. Each hemisphere is divided into four lobes, named from the front (rostral) to back (caudal) of the brain frontal, temporal, parietal and occipital. 

An inevitable consequence of ageing is an elevation of brain iron in specific brain regions, e.g. in the putamen, motor cortex, pre-frontal cortex, sensory cortex and thalamus, localized within H- and L-ferritin and neuromelanin with no apparent adverse effect. However, ill-placed excessive amounts of iron in specific brain cellular constituents, such as mitochondria or in specific regions brain, e.g. in the substantia nigra and lateral globus pallidus, will lead to neurodegenerative diseases (Friedreich s ataxia and Parkinson s disease (PD), respectively). We discuss here a few of the examples of the involvement of iron in neurodegenerative diseases. From more on iron metabolism see Crichton, 2001. 

In the brain, methamphetamine causes massive amounts of the neurotransmitters dopamine, norepinephrine, and serotonin to be released from neurons in the brain, particularly in the limbic system and frontal cortex. Scientists believe the increased dopamine release in these brain regions is responsible for methamphetamine s ability to keep people awake, alert, energetic, active, and possibly addicted. Methamphetamine acts on a variety of brain regions to produce a number of different effects (Table 2.1). 

A global view of consciousness is that it is generated throughout the entire brain, as a result of synchronisation of relevant neural networks. Specific systems or regions—for example the cerebral cortex, brainstem reticular formation and thalamic nuclei—may be key anatomical integrators. Areas with the most widespread interconnections are pivotal, and on this basis the cortex and thalamus are more relevant than cerebellum and striatum for example. Frontal cortex for example connects with every other brain region, both in terms of input and output, with 80% of such connections accounted for by cortico-cortical connections. Thalamic intralaminar nuclei are, in conjunction with the reticular nucleus, reciprocally connected to all cortical areas. By contrast the cerebellum has very few output pathways and striatal-cortical input is (via the thalamus) confined to frontal lobe. 

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