Cortex somatosensory

Commins, D.L., and Seiden, L.S. Alpha-methyltyrosine blocks methylamphetamine-induced degeneration in the rat somatosensory cortex. Brain Res 365 15-20, 1986. 

In that and subsequent studies (Kosofsky 1985 Blue et al. 1988a), a distinct laminar pattern of innervation was found in somatosensory cortex, and a quite different pattern in the cingulate cortex, hippocampus, and dentate gyrus, where there are distinct bands of highly varicose axons. In the primate, the 5-HT innervation of cerebral cortex is denser and more highly differentiated among different architectonic and functional areas (Kosofsky et al. 1984 Morrison et al. 1982 Morrison and Foote 1986 Wilson and Molliver 1986 Wilson et al. 1989). For example, marked differences in the density and distribution of 5-HT axons are found in the macaque on either side of the central sulcus, in primary motor and somatosensory cortex while... 

FIGURE 1. Marked reduction of serotonin-immunoreactive axons in the somatosensory cortex of... 

These ascending sensory pathways cross from one side of the CNS to the other so that sensory input from the left side of the body is transmitted to the somatosensory cortex of the right cerebral hemisphere and visa versa. Therefore, damage to this region of cortex in a given hemisphere results in... 

The posterior parietal cortex is located posterior to the somatosensory cortex and serves as its unimodal association area. In addition to further processing of somatosensory input, information from the somatosensory cortex is integrated with visual inputs in this region. Association tracts from both the somatosensory cortex and the visual cortex terminate here. This activity is important for planning complex movements and for hand (prop-rioception)-eye (visual) coordination. 

As discussed, the first-order neuron is the afferent neuron that transmits impulses from a peripheral receptor toward the CNS. Its cell body is located in the dorsal root ganglion. This neuron synapses with the second-order neuron whose cell body is located in the dorsal horn of the spinal cord or in the medulla of the brainstem. The second-order neuron travels upward and synapses with the third-order neuron, whose cell body is located in the thalamus. Limited processing of sensory information takes place in the thalamus. Finally, the third-order neuron travels upward and terminates in the somatosensory cortex where more complex, cortical processing begins. 

Figure 8.1 The pain pathway. The pain signal is transmitted to several regions of the brain, including the thalamus reticular formation hypothalamus limbic system and somatosensory cortex. Each region carries out a specific aspect of the response to pain.

The cell bodies of third-order sensory neurons are located in the thalamus. These neurons transmit the pain signal to the somatosensory cortex. The function of this region of the brain is to localize and perceive the intensity of the painful stimulus. Further transmission of the signal to the association areas of the cerebral cortex is important for the perception and meaningfulness of the painful stimulus. 

Ueki, M., Mies, G. and Hossmann, K. A. Effect of alpha-chloralose, halothane, pentobarbital and nitrous oxide anesthesia on metabolic coupling in somatosensory cortex of rat. Acta Anaesthesiol. Scand. 36 318-322,1992. 

Similar maps exist in other parts of the brain for example, the areas concerned with sensory input such as the primary somatosensory cortex (see Figure 1.3). Such brain maps of the body are important because information from various organs converge on the brain in a highly organized fashion and can therefore be reflected at all levels of information processing. Such... 

In SUMMARY, areas of the cerebral cortex can be identified according to the bodily functions which they control. For example, the motor cortex for muscle control, somatosensory cortex for sensory input, visual cortex for visual input, an area concerned with speech, etc. In addition to these specific areas, the cortex also contains highly developed association areas which are probably involved in the complex synthesis of information. 

Rebsam A, Seif I, Gaspar P (2002) Refinement of thalamocortical arbors and emergence of barrel domains in the primary somatosensory cortex a study of normal and monoamine oxidase aknock-out mice. J Neurosci 22 8541-8552... 

Vitalis T, Cases O, Gillies K, Hanoun N, Hamon M, Seif 1, Caspar P, Kind P, Price DJ (2002) Interactions between TrkB signaling and serotonin excess in the developing murine somatosensory cortex a role in tangential and radial organization of thalamocortical axons. J Neurosci 22 4987-5000... 

Buhl EH, Tamas G, Fisahn A (1998) Cholinergic activation and tonic excitation induce persistent gamma oscillations in mouse somatosensory cortex in vitro. J Physiol (Lond) 513 117-126... 

The area of the brain enclosing the third ventricle is the diencephalon. This area consists of several important structures, including the thalamus and hypothalamus. The thalamus contains distinct nuclei that are crucial in the integration of certain types of sensations and their relay to other areas of the brain (such as the somatosensory cortex). The hypothalamus is involved in the control of diverse body functions including temperature control, appetite, water balance, and certain emotional reactions. The hypothalamus is also... 

Young-Davies CL, Bennett-Clarke CA, Lane RD, Rhoades RW. Selective facilitation of the serotonin (IB) receptor causes disorganization of thalamic afferents and barrels in somatosensory cortex of rat. J Comp Neurol 2000 425 130-138. 

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