Fox Kevin, Wallace Helen, Glazewski Stanislaw
School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, UK.
Philos Trans R Soc Lond B Biol Sci. 2002 Dec 29;357(1428):1709-15. doi: 10.1098/rstb.2002.1169.
Sensory deprivation and injury to the peripheral nervous system both induce plasticity in the somatosensory system of adult animals, but in different places. While injury induces plasticity at several locations within the ascending somatosensory pathways, sensory deprivation appears only to affect the somatosensory cortex. Experiments have been performed to detect experience-dependent plasticity in thalamic receptive fields, thalamic domain sizes and convergence of thalamic receptive fields onto cortical cells. So far, plasticity has not been detected with sensory deprivation paradigms that cause substantial cortical plasticity. Part of the reason for the lack of thalamic plasticity may lie in the synaptic properties of afferent systems to the thalamus. A second factor may lie in the differences in the organization of cortical and thalamic circuits. Many deprivation paradigms induce plasticity by decreasing phasic lateral inhibition. Since lateral inhibition appears to be far weaker in the thalamus than the cortex, sensory deprivation may not cause large enough imbalances in thalamic activity to induce plasticity in the thalamus.
感觉剥夺和外周神经系统损伤均会在成年动物的体感系统中诱导可塑性，但发生的部位不同。损伤会在体感上行通路的多个位置诱导可塑性，而感觉剥夺似乎仅影响体感皮层。已经开展了实验来检测丘脑感受野、丘脑区域大小以及丘脑感受野向皮层细胞的汇聚中依赖经验的可塑性。到目前为止，在导致显著皮层可塑性的感觉剥夺范式中尚未检测到可塑性。丘脑缺乏可塑性的部分原因可能在于丘脑传入系统的突触特性。第二个因素可能在于皮层和丘脑回路组织的差异。许多剥夺范式通过减少相位性侧向抑制来诱导可塑性。由于侧向抑制在丘脑中似乎比在皮层中弱得多，感觉剥夺可能不会在丘脑中引起足够大的活动失衡以诱导丘脑可塑性。
