Brain orbitofrontal cortex

Hopefully the combination of TMS with fMRI will enable the more precise location of the regional dysfunction in depression to be located and thereby enable the neuronal pathways concerned to be identified. To date, the early studies of TMS with fMRI have shown that the effects of TMS occur in brain regions distant from the site of stimulation, including the caudate, orbitofrontal cortex and the cerebellum. 

Functional neuroimaging studies provide strong evidence for dysfunction of the cortical-striatal-thalamocortical (CSTC) circuitry. Symptoms of OCD are associated with increased activity in orbitofrontal cortex in neutral state (Swedo et ah, 1989b Baxter, 1994 Saxena et ah, 1998). Increased activity was also noted in some of these studies in anterior cingulate gyrus, caudate nucleus, and thalamus. Horwitz et al. (1991) found that the pattern of intercorrelations between various brain regions in patients with OCD differed from that of controls. 

Garey LJ, Von Bussmann KA, Hirsch SR. 2006. Decreased numerical density of kainate receptor-positive neurons in the orbitofrontal cortex of chronic schizophrenics.Exp Brain Res. 173(2) 234-42. 

Mitral and tufted cells in the olfactory bulb project their axons to the olfactory cortex, the site thought to integrate the signals from distinct glomeruli. The olfactory signals processed in the olfactory cortex are sent to a variety of higher centers of the brain, which include insular cortex, orbitofrontal cortex, amygdale, hippocampus, and the nucleus accumbens.205... 

Figure 37.14 shows a diagram of the H2 coil, which is designed to stimulate deep brain regions and fit the human head. The effective part of the coil in contact with the patient scalp has a shape of half a donut, with 10 strips of 14—22 cm length (Figure 37.14). These strips produce the most effective field of the coil, and are oriented in a right-left direction (lateral-medial axis). Three strips pass in front of the forehead along the orbitofrontal cortex (1-3 in Figure 37.14), with a separation of 1 cm between them. Seven strips pass above the forehead along the prefrontal cortex (4-10 in Figure 37.14), with 0.8-cm separation.

The main components of brain limbic system are amygdala, orbitofrontal cortex, sensory cortex, and thalamus. This part of brain is involved in the emotional processing and learning (Bechara et al. 2000 Rolls 2000). In what follows, the primary components of the brain limbic system are briefly described and then a mathematical model of brain limbic system is introduced. Finally, the mathematical model is integrated with a PID and a semiactive inversion algorithm to develop a... 

A mathematical relationship between the components of brain limbic system was proposed by Moren and Balkenius (2000) from the descriptive physical model of the limbic system that provides a qualitative sense of the overall functioning of the system. Figure 2 shows the structure of the Moren-Balkenius computational BEL model. As depicted in the figure, the BEL model has four components of the so-called limbic system of the brain amygdala, orbitofrontal cortex, sensory cortex and thalamus. Of them, amygdala and orbitofrontal cortex perform an important function in emotional processing (Moren and Balkenius 2000). 

Meador-Woodruffetal. (1997) quantified the levels of mRNA molecules encoding the five dopamine receptors in postmortem brain samples from 16 schizophrenic patients and 9 control subjects and found a dramatic decrease of dopamine recep tor transcripts in the prefrontal cortex but restricted to the D3 and D4 receptors and localized to Brodmann area 11 (orbitofrontal cortex). No differences were found in striatum or visual cortex. 

The prefrontal cortex (PFC) is the anterior part of the frontal lobes of the brain. It lies in front of the motor and premotor areas. The PFC is divided into the lateral, orbitofrontal, and medial prefrontal areas (Barbas and Pandya, 1987, 1989). Comprehensive reviews of this structure and functions of the PFC have been published in various forms (Fuster, 1997 Goldman-Rakic, 1987 Miller and Cohen, 2001 Passingham, 1993 Tanji and Hoshi, 2008). The PFC possesses a wealth of anatomical connectivity with multiple cortical and subcortical areas, and is involved in broad aspects of behavioral control. The PFC has been implicated in complex cognitive behaviors, social behaviors, and personality expression. Recent studies of this area have revealed its role in the control of a much broader spectrum of functions, such as cross-modal and cross-temporal association of information, in the executive control of behavior, and in the top-down control of neural networks involving the cortical and subcortical areas. Among them, the executive control of action was a term coined to capture various aspects of PFC function. 

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