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Dendritic dynamics and the perceptual threshold

树突动力学和感知阈值

基本信息

批准号：
250048060
负责人：
Professor Matthew Larkum
金额：
--
依托单位：
Arbeitsgruppe Neuronale Plastizität
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/250048060?language=en
关键词：
Dendritic dynamics perceptual threshold

项目摘要

Experimental and psychophysical experiments have established that the process of conscious perception is correlated to the integration of top-down signals with bottom-up information in primary sensory areas. Here, top-down signals arising from other cortical areas are thought to constitute internal representations and/or predictions about sensory information that is carried by the bottom-up stream. Although, the influence of top-down information can be clearly demonstrated with recordings of the activity of neurons, per se, it is not yet known what the underlying mechanisms are nor why they are so crucial. Layer 5 pyramidal neurons have been shown to be capable of explosive firing activity when the top and the bottom of the neuron are both simultaneously activated. This is important because axons carrying top-down information arrive in layer 1 of the cortex and bottom-up signals arrive at the lower (perisomatic) regions of the pyramidal neuron. It has been suggested therefore that top-down information is linked to bottom-up information in these cells via dendritic spikes. These spikes depend on calcium channels in the apical dendrite. We therefore propose the 'Dendrite Hypothesis' for cortex-based perception: 'Perception depends on the generation of dendritic calcium spikes in pyramidal neurons by the combined inputs of bottom-up and top-down signals'. This hypothesis has the advantage that it leads to a specific prediction, i.e. that dendritic Ca2+ transients should be involved in the perceptual process. This can be tested using conventional methodologies. Here, we propose to investigate this hypothesis by examining the events that occur around the 'perceptual threshold', i.e. events occurring after a stimulus ranging in intensity from undetectable to detectable. Animals will be trained to respond to whisker stimuli with a defined response behaviour that is then used as the assay for object perception. We will measure changes in dendritic calcium activity around the perceptual threshold using state-of-the-art techniques including 2-photon imaging and a fiberoptic imaging system ('Periscope' system) developed in our laboratory. We will test the necessity for dendritic spiking in process of perception by using optogenetic approaches for preventing dendritic spikes and top-down signals.

实验和心理物理实验已经证实，有意识的知觉过程与初级感觉区域自上而下的信号和自下而上的信息的整合有关。在这里，来自其他皮质区域的自上而下的信号被认为构成了关于自下而上的流所携带的感觉信息的内部表示和/或预测。虽然，自上而下的信息的影响可以通过神经元活动的记录清楚地展示出来，但本质上还不知道潜在的机制是什么，也不知道为什么它们如此关键。当神经元的顶部和底部同时被激活时，第5层锥体神经元被证明能够产生爆炸性的放电活动。这一点很重要，因为携带自上而下信息的轴突到达皮质的第一层，而自下而上的信号到达锥体神经元的下部(周边区)。因此，有人认为，自上而下的信息与这些细胞中的自下而上的信息通过树突棘联系在一起。这些尖峰依赖于顶端树突中的钙通道。因此，我们提出了基于皮层的知觉的“树枝状假说”：“知觉依赖于自下而上和自上而下信号的组合输入在锥体神经元中产生树突状钙尖峰”。这一假说的优点是它导致了一种特定的预测，即树突状钙瞬变应该参与感知过程。这可以使用传统方法进行测试。在这里，我们建议通过检查发生在感知阈值附近的事件来研究这一假设，即在强度从不可检测到可检测的刺激之后发生的事件。将训练动物对胡须刺激做出明确的反应行为，然后将其用作物体感知的测试。我们将使用最先进的技术，包括双光子成像和我们实验室开发的光纤成像系统(‘Periscope’系统)，测量感知阈值附近树突状钙活动的变化。我们将通过使用光遗传学方法来防止树突尖峰和自上而下的信号，来测试知觉过程中树突尖峰的必要性。