Weiss N, Ohara S, Johnson K O, Lenz F A
Department of Neurosurgery, Meyer Bldg. 7-113, Johns Hopkins Hospital, 600 North Wolfe St., Baltimore, MD 21287-7713, USA.
J Neurophysiol. 2009 Feb;101(2):1033-42. doi: 10.1152/jn.90990.2008. Epub 2008 Nov 12.
Although the response of human cutaneous mechanoreceptors to controlled stimuli is well studied, it is not clear how these peripheral signals may be reflected in neuronal activity of the human CNS. We now test the hypothesis that individual neurons in the human thalamic principal somatic sensory nucleus [ventral caudal (Vc)] respond selectively to the optimal stimulus for one of the four mechanoreceptors. The optimal stimuli for particular mechanoreceptors were defined as follows: Pacinian corpuscles (PC), vibration at 128 Hz; rapidly adapting (RA), vibration at 32 or 64 Hz; slowly adapting type 1 (SA1), edge; slowly adapting type 2 (SA2), skin stretch. Nineteen neurons had a significant response to at least one optimal stimulus, and 17 had a significantly greater response to one stimulus than to the other three, including 7 PC-related, 7 RA-like, 3 SA1-like, and 2 SA2-like neurons. One of each of the SA1- and SA2-like thalamic neurons responded to vibration with firing rates that were lower than those to edge or stretch but not significantly. Except in the case of PC-related neurons, the receptive field (RF) sizes were larger for these thalamic neurons than for the corresponding mechanoreceptor. Von Frey thresholds were higher than those for the corresponding human RA and SA1 mechanoreceptors. These results suggest that there is a convergence of pathways transmitting input from multiple mechanoreceptors of one type on single thalamic neurons via the dorsal columns. They are also consistent with the presence of primate thalamic elements of modality and somatotopic isorepresentation.
尽管人类皮肤机械感受器对可控刺激的反应已得到充分研究，但尚不清楚这些外周信号如何在人类中枢神经系统的神经元活动中得到体现。我们现在检验这样一个假设：人类丘脑主要躯体感觉核[腹侧尾核（Vc）]中的单个神经元会选择性地对四种机械感受器之一的最佳刺激做出反应。特定机械感受器的最佳刺激定义如下：帕西尼小体（PC），128赫兹的振动；快速适应（RA），32或64赫兹的振动；慢适应1型（SA1），边缘刺激；慢适应2型（SA2），皮肤伸展。19个神经元对至少一种最佳刺激有显著反应，17个神经元对一种刺激的反应明显大于对其他三种刺激的反应，其中包括7个与PC相关的神经元、7个类RA神经元、3个类SA1神经元和2个类SA2神经元。类SA1和类SA2丘脑神经元中的各一个对振动的反应发放率低于对边缘或伸展刺激的发放率，但差异不显著。除了与PC相关的神经元外，这些丘脑神经元的感受野（RF）大小比相应的机械感受器更大。冯·弗雷阈值高于相应的人类RA和SA1机械感受器。这些结果表明，存在一条通过背柱将来自一种类型的多个机械感受器的输入传递到单个丘脑神经元的通路汇聚。它们也与灵长类丘脑模态和躯体定位等表征元素的存在相一致。
