A simple decision to move in response to touch reveals basic sensory memory and mechanisms for variable response times.
A simple decision to move in response to touch reveals basic sensory memory and mechanisms for variable response times.
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DOI：
10.1113/jp276356
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发表时间：
2018-12
期刊：
影响因子：
--
通讯作者：
Roberts A
中科院分区：
文献类型：
--
作者：
Koutsikou S;Merrison-Hort R;Buhl E;Ferrario A;Li WC;Borisyuk R;Soffe SR;Roberts A
短期工作记忆和决策通常在大脑皮层进行研究；在许多简单决策的模型中，感觉信号在长时间、可变的延迟后缓慢而嘈杂地建立到阈值，以启动运动反应。当被触摸时，刚孵化的青蛙蝌蚪决定是否游泳；我们定义了游泳的长期和可变延迟，并使用全细胞记录来揭示负责的神经元和过程。感觉和感觉通路神经元的放电潜伏期短，而且太短和不变，无法解释这些延迟，而控制游泳的后脑网状脊髓神经元的记录显示，突触兴奋的长期和可变的积聚可以达到放电阈值并开始游泳。我们认为，这种兴奋提供了对刺激的感觉记忆，可能是由小型反射后脑网络产生的。我们的结果揭示了基本的网络机制，使动物能够记住短暂的感觉刺激，并推迟简单的运动决定。许多对感觉输入的运动反应，如运动或眼球运动，都比反射慢得多。更简单的动物能提供关于运动决定的细胞机制的基本答案吗？我们能观察到激励的“积累”到为其他地方的决策奠定基础的门槛吗？我们探索了体感触摸刺激是如何导致决定在刚孵化的非洲爪哇蝌蚪中游泳的。在表现良好和不活动的蝌蚪身上，游泳的延迟时间很长，而且是可变的。他们被广泛研究的感觉和感觉通路神经元的活动太短暂，无法解释这些反应延迟。相反，来自驱动游泳的后脑网状脊髓神经元的全细胞记录显示，这些神经元在短暂的刺激后，会收到持续时间较长的、可变的突触兴奋，持续近一秒。当这种兴奋达到临界值时，它们就会开火并开始游泳。对兴奋总和的分析要求我们提出目前未定义的突触前后脑神经元的延长放电。简单的模型表明，在感觉通路中插入一个小的兴奋性递归网络可以模拟这一过程。我们认为，这样的网络可能会产生缓慢的、可变的激励与阈值之和。这种兴奋提供了对感官刺激的简单记忆。它允许感觉输入的时间和空间整合，并解释了游泳的长时间、可变延迟。这一过程类似于哺乳动物大脑皮层回路中兴奋的“积累”。我们得出的结论是，感觉记忆和决策的基本要素存在于脑干中，这是令人惊讶的早期发育阶段。短期工作记忆和决策通常在大脑皮层进行研究；在许多简单决策的模型中，感觉信号在长时间、可变的延迟后缓慢而嘈杂地建立到阈值，以启动运动反应。当被触摸时，刚孵化的青蛙蝌蚪决定是否游泳；我们定义了游泳的长期和可变延迟，并使用全细胞记录来揭示负责的神经元和过程。感觉和感觉通路神经元的放电潜伏期短，而且太短和不变，无法解释这些延迟，而控制游泳的后脑网状脊髓神经元的记录显示，突触兴奋的长期和可变的积聚可以达到放电阈值并开始游泳。我们认为，这种兴奋提供了对刺激的感觉记忆，可能是由小型反射后脑网络产生的。我们的结果揭示了基本的网络机制，使动物能够记住短暂的感觉刺激，并推迟简单的运动决定。
Short‐term working memory and decision‐making are usually studied in the cerebral cortex; in many models of simple decision making, sensory signals build slowly and noisily to threshold to initiate a motor response after long, variable delays. When touched, hatchling frog tadpoles decide whether to swim; we define the long and variable delays to swimming and use whole‐cell recordings to uncover the neurons and processes responsible. Firing in sensory and sensory pathway neurons is short latency, and too brief and invariant to explain these delays, while recordings from hindbrain reticulospinal neurons controlling swimming reveal a prolonged and variable build‐up of synaptic excitation which can reach firing threshold and initiate swimming. We propose this excitation provides a sensory memory of the stimulus and may be generated by small reverberatory hindbrain networks. Our results uncover fundamental network mechanisms that allow animals to remember brief sensory stimuli and delay simple motor decisions. Many motor responses to sensory input, like locomotion or eye movements, are much slower than reflexes. Can simpler animals provide fundamental answers about the cellular mechanisms for motor decisions? Can we observe the ‘accumulation’ of excitation to threshold proposed to underlie decision making elsewhere? We explore how somatosensory touch stimulation leads to the decision to swim in hatchling Xenopus tadpoles. Delays measured to swimming in behaving and immobilised tadpoles are long and variable. Activity in their extensively studied sensory and sensory pathway neurons is too short‐lived to explain these response delays. Instead, whole‐cell recordings from the hindbrain reticulospinal neurons that drive swimming show that these receive prolonged, variable synaptic excitation lasting for nearly a second following a brief stimulus. They fire and initiate swimming when this excitation reaches threshold. Analysis of the summation of excitation requires us to propose extended firing in currently undefined presynaptic hindbrain neurons. Simple models show that a small excitatory recurrent‐network inserted in the sensory pathway can mimic this process. We suggest that such a network may generate slow, variable summation of excitation to threshold. This excitation provides a simple memory of the sensory stimulus. It allows temporal and spatial integration of sensory inputs and explains the long, variable delays to swimming. The process resembles the ‘accumulation’ of excitation proposed for cortical circuits in mammals. We conclude that fundamental elements of sensory memory and decision making are present in the brainstem at a surprisingly early stage in development. Short‐term working memory and decision‐making are usually studied in the cerebral cortex; in many models of simple decision making, sensory signals build slowly and noisily to threshold to initiate a motor response after long, variable delays. When touched, hatchling frog tadpoles decide whether to swim; we define the long and variable delays to swimming and use whole‐cell recordings to uncover the neurons and processes responsible. Firing in sensory and sensory pathway neurons is short latency, and too brief and invariant to explain these delays, while recordings from hindbrain reticulospinal neurons controlling swimming reveal a prolonged and variable build‐up of synaptic excitation which can reach firing threshold and initiate swimming. We propose this excitation provides a sensory memory of the stimulus and may be generated by small reverberatory hindbrain networks. Our results uncover fundamental network mechanisms that allow animals to remember brief sensory stimuli and delay simple motor decisions.
影响因子：
3.7
作者：
Marshall JA;Bogacz R;Gilchrist ID
通讯作者：
Gilchrist ID
影响因子：
3.5
作者：
Hull MJ;Willshaw DJ
通讯作者：
Willshaw DJ