Neuroscience Research Institute and Department of Neurobiology, Peking University Health Science Center, Beijing, China.
Mol Pain. 2011 Aug 24;7:64. doi: 10.1186/1744-8069-7-64.
The ability to encode noxious stimulus intensity is essential for the neural processing of pain perception. It is well accepted that the intensity information is transmitted within both sensory and affective pathways. However, it remains unclear what the encoding patterns are in the thalamocortical brain regions, and whether the dual pain systems share similar responsibility in intensity coding.
Multichannel single-unit recordings were used to investigate the activity of individual neurons and neuronal ensembles in the rat brain following the application of noxious laser stimuli of increasing intensity to the hindpaw. Four brain regions were monitored, including two within the lateral sensory pain pathway, namely, the ventral posterior lateral thalamic nuclei and the primary somatosensory cortex, and two in the medial pathway, namely, the medial dorsal thalamic nuclei and the anterior cingulate cortex. Neuron number, firing rate, and ensemble spike count codings were examined in this study. Our results showed that the noxious laser stimulation evoked double-peak responses in all recorded brain regions. Significant correlations were found between the laser intensity and the number of responsive neurons, the firing rates, as well as the mass spike counts (MSCs). MSC coding was generally more efficient than the other two methods. Moreover, the coding capacities of neurons in the two pathways were comparable.
This study demonstrated the collective contribution of medial and lateral pathway neurons to the noxious intensity coding. Additionally, we provide evidence that ensemble spike count may be the most reliable method for coding pain intensity in the brain.
编码有害刺激强度的能力对于疼痛感知的神经处理至关重要。人们普遍认为，强度信息在感觉和情感通路中都有传递。然而，在丘脑皮质脑区中，编码模式是什么，以及双痛系统是否在强度编码方面具有相似的责任，这些问题仍不清楚。
使用多通道单细胞记录技术，在向足底施加递增强度的有害激光刺激后，研究了大鼠大脑中单个神经元和神经元集合的活动。监测了四个脑区，包括外侧感觉痛通路内的两个脑区，即腹后外侧丘脑核和初级体感皮层，以及内侧通路内的两个脑区，即内侧背侧丘脑核和前扣带皮层。在这项研究中，检查了神经元数量、放电率和集合尖峰计数编码。我们的结果表明，有害激光刺激在所有记录的脑区都引起了双峰反应。在激光强度与反应神经元数量、放电率以及尖峰计数总和（MSC）之间发现了显著的相关性。MSC 编码通常比其他两种方法更有效。此外，两条通路中的神经元的编码能力相当。
这项研究表明，内侧和外侧通路神经元对有害强度编码有共同的贡献。此外，我们提供的证据表明，集合尖峰计数可能是大脑中编码疼痛强度最可靠的方法。
