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The postcentral gyrus is ~ above the lateral surface ar of the parietal lobes in between the main sulcus and postcentral sulcus. The postcentral gyrus has the major somatosensory cortex, a significant mind region responsible for proprioception.<1> This region perceives various somatic emotion from the body, consisting of touch, pressure, temperature, and pain.<2> After stimulation, this peripheral somatosensory receptors relay through the dorsal spinal cord and terminate in the postcentral gyrus whereby the stimuli space perceived.<3>
Structure and also Function
The postcentral gyrus is uncovered on the lateral surface of the anterior parietal lobe, caudal to the central sulcus, and also corresponds come Brodmann areas 3b, 1, and also 2.<4> The primary somatosensory cortex perceives sensations on the contralateral side. The topographic company of this an ar is well-known as the sensory homunculus, or “little man.” This organization of the somatosensory map is such that the medial element is responsible for reduced extremity sensation, the dorsolateral aspect is responsible for the top extremity, and also the many lateral facet is responsible for the face, lips, and tongue.<5> However, areas of the homunculus that require high sensory acuity and also resolution take it up a bigger area ~ above the somatosensory map. For example, the hands, face, and lips necessitate fine somatosensory perception relative to various other regions, such as the foot or torso.<5><6> The postcentral gyrus also houses the an additional somatosensory cortex, which appears to pat a function in the integration of somatosensory stimuli and also memory formation.<7>
The early main nervous system an initial appears as the neural tube. Over time, the anterior portion of the neural tube develops into the forebrain, midbrain, and hindbrain, and also the dorsal neural tube differentiates to become the somatosensory pathway in the mind and spinal cord.<8> In the forebrain, a selection of aspect gradients, consisting of SHH, WNT, and BMP, offers rise come the telencephalon.<9> By the end of the fifth month the development, the central sulcus has created separating the precentral and also postcentral gyri.<10> Between the late 3rd trimester and also birth, the primary somatosensory cortex spatially differentiates creating the topographic sensory map.<11>
Blood Supply and Lymphatics
The anterior and also middle cerebral arteries carry out the postcentral gyrus blood supply. The anterior cerebral artery is responsible for perfusing the medial third of the postcentral gyrus, if the middle cerebral artery perfuses the lateral two-thirds the the postcentral gyrus. Venous blood drains through the premium sagittal sinus because that the remarkable two-thirds the the postcentral gyrus and also the superficial Sylvian veins to the transverse sinus because that the inferior 3rd of the postcentral gyrus.<12>
Dorsal Column-Medial Lemniscus Pathway
The dorsal column-medial lemniscus pathway is the main somatosensory pathway because that fine touch, vibration, two-point discrimination, and also proprioception. This pathway is made up of 3 neurons that attach the mechanoreceptor to its specific an ar within the main somatosensory cortex. Meissner"s corpuscles, Merkel"s disks, and Ruffini"s corpuscles are stimulated by touch, vibration, and also skin tension, respectively bring about the production of an activity potential in the first-order neuron.<13> These first-order neurons space pseudounipolar v their cell bodies found in the dorsal source ganglion.<14> Axons below the T6 level take trip up the medial dorsal pillar as the fasciculus gracilis, while axons over the T6 level take trip up the lateral dorsal pillar as the fasciculus cuneatus.<15><16> these columns synapse through the second-order neurons in the cell nucleus gracilis and also nucleus cuneatus in the medulla. The second-order neurons crossover to the contralateral side and also ascend, developing the medial lemniscus. Choose the dorsal columns, the medial lemniscus is likewise spatially organized. However, fairly than gift structured in a medial come the lateral direction, the reduced extremity axons are found much more ventrally, and also the top extremity axons more dorsal. The medial lemniscus continues into the midbrain and also synapses in the ventral posterior nucleus of the thalamus.<14> Again, these synapses topographically organize v the ventral posterolateral cell nucleus responsible because that somatosensation of the body and also the ventral posteromedial cell nucleus responsible because that somatosensation of the head.<17> Finally, the third-order neurons ascend with the posterior inner capsule to the specific an ar within the main somatosensory cortex.<14>
The spinothalamic street (also known as the ventrolateral system) is the somatosensory pathway because that crude touch, pressure, nociception, and temperature. The spinothalamic tract divides into two systems; the anterior spinothalamic system is responsible for crude touch and pressure, and the lateral spinothalamic mechanism is responsible because that pain and also temperature sensation.
In the anterior spinothalamic system, A-beta fibers moving crude touch and also pressure stimuli travel through the dorsal source ganglion and also synapse in the ipsilateral dorsal horn. A-beta fibers space myelinated and also have a large diameter compared to other fiber varieties in the spinothalamic tract.<18> The second-order neuron passes through the anterior white commissure the the spinal cord and also ascends together the anterior spinothalamic tract on the contralateral side. Axons from the body synapse in the ventral posterolateral thalamus and also third-order neurons travel v the posterior limb of the internal capsule and also terminate in your appropriate region within the postcentral gyrus.
Unlike the anterior spinothalamic system, the lateral spinothalamic mechanism is comprised of many nerve fiber types. A-delta fibers are myelinated nerves v a smaller diameter than A-beta fibers.<18> Type ns A-delta fibers respond to mechanical and chemical stimuli but have a high threshold the activation for heat stimuli, whereas form II A-delta fibers room sensitive to heat and have a high mechanically threshold.<18> Together, A-delta fiber afferents signal because that the "first" pains response, a quick nociceptive stimulation the triggers a reflex arc to remove the human body from the painful stimulus.<19> C-fibers space unmyelinated, small diameter nociceptive nerves that deserve to respond come mechanical and also temperature stimuli.<18> C-fibers are progressively conducting neurons responsible for the "second" pain, the burning, or aching pain linked with an injury.<19> Like the anterior spinothalamic system, the lateral spinothalamic device synapses in the dorsal horn and crosses to the contralateral next at the same level of the spinal cord; however, this fibers ascend together the lateral spinothalamic tract. Again, these fibers will certainly synapse in the ventral posterolateral cell core of the thalamus, travel with the corona radiata, and also synapse in the correct topographic region within the main somatosensory cortex.<18><19>
Although there are interhemispheric and interindividual sports in the pistol appearance the postcentral gyri, the overall topographic sensory circulation remains the same.<20> However, postcentral gyrus grey issue volume has shown to correlate positively with enhanced somatosensory processing.<21>
Common surgical considerations regarding the postcentral gyrus or structures close to the postcentral gyrus, such as the precentral gyrus, posterior parietal lobe, or insula, incorporate tumor resection surgery, brain mapping for therapy of seizures, and treatment the neurodegenerative diseases. Cancers that deserve to manifest close to the postcentral gyrus encompass gliomas, astrocytomas, oligodendrogliomas, and meningiomas. Patients with lesions in the primary somatosensory cortex experience somatosensory deficits, specifically in the hands and also face.<22> Uncontrolled growth of this tumors close to or within the postcentral gyrus renders surgical resection challenging to perform without any post-operative somatosensory loss. However, new developments in cerebral tumor resection approaches have presented improvements in glioma and meningioma microsurgery resections close to the postcentral gyrus.<23><24><25> Another innovation in tumor resection surgeries has actually been preoperative transcortical magnetic stimulation in conjunction v fMRI. This method has presented to improve resection spare part in precentral glioma resections and also preserve motor functions.<26><27> Repetitive transcranial magnetic stimulations have displayed to enhance tactile discrimination and reorganize the somatosensory map.<28><29>
Other surgical considerations entailing the postcentral gyrus are the usage of deep brain stimulation because that the therapy of Parkinson disease. Patients with Parkinson an illness undergo deep brain stimulation and also dopaminergic therapy to correct engine deficits. The subthalamic nucleus and also globus pallidus internus room two usual targets for deep mind stimulation to treat engine symptoms watched in Parkinson disease.<30> Unfortunately, these therapies have the right to negatively affect somatosensation and the main somatosensory cortex. Positron emissions tomography and also magnetoencephalography disclose deep mind stimulation can an outcome in deleterious impacts on somatosensation while properly treating Parkinson disease-related engine symptoms.<31><32> It is important to monitor patient undergoing deep brain stimulation come ensure they are not experiencing any kind of lasting sensory deficits.
The postcentral gyrus is at threat of damage due to strokes. The two significant arteries the supply the postcentral gyrus space the anterior and also middle cerebral arteries. Sensory deficits deserve to often assist to identify which artery is impacted and the place of the infarct. Because that example, ischemic punch in the anterior cerebral artery will impact the medial postcentral gyrus and may current with sensory deficits in the contralateral leg. A stroke in the center cerebral artery may display a contralateral sensory lose in the challenge or upper extremity, depending on the location of the infarct. Cerebral infarctions to this arteries will often have accompanying motor deficits, aphasia, and also visual deficits depending upon the ar of the occlusion.
Nociception pathways can be suppressed through ascending and also descending modulating pathways. The pain perception circuit in the mind includes the main somatosensory cortex, insula, anterior cingulate gyrus, prefrontal cortex, and also thalamus.<33> These regions are essential for the perception of the ache stimulus and also play a role in learning and memory to avoid the painful economic stimulation from developing in the future. Return this mechanism is necessary for responding come acute pain, dysregulation that the nociceptive pathway can lead come chronic pathologic pain. Descending pain modulating pathways duty to avoid chronic pain, which might manifest together overactive and hypersensitive nociception.
Descending ache modulating pathways show up to originate in the periaqueductal grey and also rostroventral medial medulla.<34> Activation that the descending pain modulating pathway leads to the activation of inhibitory interneurons in the spinal cord and also subsequent release of endogenous opioids and also acetylcholine.
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<35><36> Opioid ligands tie to the presynaptic receptor hyperpolarizing the neuron and preventing the release of substance P, thus stopping the infection of the painful economic stimulation while leaving non-nociceptive emotion intact.<35> This pathway is additionally the target because that exogenous opioid pharmacotherapy because that the therapy of pain. However, presynaptic opioid receptors end up being tolerant with consistent drug therapy; prolonged opioid administration leads to the downregulation that the opioid receptors at the presynaptic neuronal surface. Therefore, patients need to not receive treatment with opiates for chronic pain.