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The barrel cortex refers to the dark-staining regions of layer four of the somatosensory cortex where somatosensory inputs from the contralateral side of the body come in from the thalamus. Barrels are found in some species of rodents and species of at least two other orders. The rest of this article will focus on the 'whisker barrels' in the somatosensory cortex of rodents. Inputs from the thalamus carrying information from a given whisker terminate in discrete areas of layer IV forming anatomically distinguishable areas (barrels) which are separated from each other by areas called septa. These structures were first discovered by Woolsey and Van der Loos (1970).〔Woosley, T.A., Van Der Loos, H. 1970. The structural organization of layer IV in the somatosensory region (SI) of mouse cerebral cortex: The description of a cortical field composed of discrete cytoarchitectonic units. ''Brain Research''. 205-238.〕 Recognizing that the array was similar to that of the vibrissae on the mystacial pad, they hypothesized that the barrels were the "cortical correlates of the mystacial vibrissae" and that "one barrel represents one vibrissa". Due to its distinctive cytoarchitectonics and functional significance, the barrel cortex has played an important role in neuroscience. The majority of what is known about corticothalamic processing comes from studying the barrel cortex and researchers have intensively studied the barrel cortex as a model of neocortical column. Neurons within the layer IV barrel cortex directly code for whisker displacement. That is to say, that the neuron within a given barrel will fire when the whisker that barrel represents is moved. These neurons also show directional sensitivity, certain neurons will only fire when the whisker is moved in a specific direction.〔Swadlow HA. Efferent neurons and suspected interneurons in S-1 vibrissa cortex of the awake rabbit: receptive fields and axonal properties. J Neurophysiol 62: 288–308, 1989〕〔Swadlow HA. Efferent neurons and suspected interneurons in second somatosensory cortex of the awake rabbit: receptive fields and axonal properties. J Neurophysiol 66: 1392–1409, 1991〕 Neurons in the barrel cortex exhibit the property of synaptic plasticity that allows them to alter the vibrissae to which they respond depending on the rodent's history of tactile experience.〔Hardingham N, Glazewski S, Pakhotin P, Mizuno K, Chapman PF, Giese KP, Fox K. Neocortical long-term potentiation and experience-dependent synaptic plasticity require alpha-calcium/calmodulin-dependent protein kinase II auto-phosphorylation. J Neurosci. 2003 Jun 1;23(11):4428-36.〕 The field of barrel cortex research has matured to the stage where a book has been published on the subject.〔Fox, K. Barrel Cortex. Cambridge, New York, Melbourne. Cambridge University Press. 2008. ISBN 978-0-521-85217-3〕 == The Posteromedial Barrel Subfield == The posteromedial barrel subfield (PMBSF) is a highly consistent region of the barrel field (Woolsey, 1978). Barrels of the PMBSF are the largest and most elliptical in shape and have a striking topographical organization that is identical to that of the major facial whiskers (also called myastacial vibrissae); these whiskers are organized into 5 rows of 4-7 large whiskers that run close to parallel with the bridge of the nose. (Woolsey and Van der Loos, 1970). A consideration of this morphology led Woolsey and Van der Loos to propose that the barrels of the PMBSF were the cortical correlates of the myastacial vibrissae; this is sometimes called the one-barrel-one-vibrissa hypothesis (Woolsey and Van der Loos, 1970). Thus each barrel in the PMBSF is thought to correspond with a single myastacial vibrissa on the contralateral side of the animal. In 1973 Woolsey and Van der Loos provided strong evidence for this hypothesis by selectively damaging individual whiskers in rodents at birth and noticing that when the brains of these animals were analyzed the corresponding barrel was not present. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「barrel cortex」の詳細全文を読む スポンサード リンク
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