Institute of Neuroscience and Center for Integrated Protein Science, Technical University Munich, Biedersteinerstrasse 29, 80802 Munich, Germany.
Nature. 2011 Jun 26;475(7357):501-5. doi: 10.1038/nature10193.
The individual functional properties and spatial arrangement of afferent synaptic inputs on dendrites have a critical role in the processing of information by neurons in the mammalian brain. Although recent work has identified visually-evoked local dendritic calcium signals in the rodent visual cortex, sensory-evoked signalling on the level of dendritic spines, corresponding to individual afferent excitatory synapses, remains unexplored. Here we used a new variant of high-resolution two-photon imaging to detect sensory-evoked calcium transients in single dendritic spines of mouse cortical neurons in vivo. Calcium signals evoked by sound stimulation required the activation of NMDA (N-methyl-D-aspartate) receptors. Active spines are widely distributed on basal and apical dendrites and pure-tone stimulation at different frequencies revealed both narrowly and widely tuned spines. Notably, spines tuned for different frequencies were highly interspersed on the same dendrites: even neighbouring spines were mostly tuned to different frequencies. Thus, our results demonstrate that NMDA-receptor-dependent single-spine synaptic inputs to the same dendrite are highly heterogeneous. Furthermore, our study opens the way for in vivo mapping of functionally defined afferent sensory inputs with single-synapse resolution.
树突上传入性突触输入的个体功能特性和空间排列在哺乳动物大脑神经元信息处理中起着关键作用。尽管最近的研究已经在啮齿动物视觉皮层中识别出了视觉诱发的局部树突钙信号，但对应于单个传入兴奋性突触的感觉诱发信号在树突棘水平上仍未被探索。在这里，我们使用一种新的高分辨率双光子成像变体，在体内检测到小鼠皮质神经元单个树突棘的感觉诱发钙瞬变。声音刺激引起的钙信号需要 NMDA（N-甲基-D-天冬氨酸）受体的激活。活性棘突广泛分布在基底和顶端树突上，在不同频率的纯音刺激下，既显示出窄带调谐棘突，也显示出宽带调谐棘突。值得注意的是，对不同频率调谐的棘突在同一树突上高度交织：即使相邻的棘突也大多调谐到不同的频率。因此，我们的结果表明，相同树突上 NMDA 受体依赖性的单个棘突突触输入具有高度异质性。此外，我们的研究为具有单突触分辨率的功能定义传入感觉输入的体内映射开辟了道路。
