Synaptic plasticity can produce and enhance direction selectivity.
Synaptic plasticity can produce and enhance direction selectivity.
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突触可塑性可以产生并增强方向选择性。
DOI：
10.1371/journal.pcbi.0040032
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发表时间：
2008-02
影响因子：
4.3
通讯作者：
Fortune ES
中科院分区：
文献类型：
--
作者：
Carver S;Roth E;Cowan NJ;Fortune ES
感知图像运动方向的识别对于控制许多动物行为至关重要。我们提出了一种简约的运动处理模型，该模型利用短期突触抑制产生方向选择反应，并可以再现弱电鱼中神经元群体中方向选择的显着特征。该模型使用基本的Reichardt运动检测器实现方向选择性：来自空间分离的接受野的信息通过动态不同的路径收敛到神经元上。在该模型中，这些差异来自不同突触的信息汇聚，这些突触要么表现出短期突触抑制，要么不表现出短期突触抑制——相对于非抑制突触，短期突触抑制产生阶段性进展。短期抑郁是用两个状态变量来建模的，一个是快速过程，时间常数在几十到几百毫秒之间，一个是缓慢过程，时间常数在几秒到几十秒之间。这些过程与自然发生的时间常数相对应，这些时间常数在表现出短期抑制的突触上观察到。包含快速过程足以产生时间差异，这是基本Reichardt电路中方向选择性所必需的。对于持续数秒或更长时间的刺激，缓慢过程的加入可以随着时间的推移增强方向选择性。瞬时（即短时间）刺激不会引起慢过程，因此不会引起方向选择性的增强。然而，在伽马频率范围内增加持续的全局同步振荡可以驱动缓慢的过程，并增强对瞬态刺激的方向选择性。然而，这种增强效应并不发生在所有模型参数的组合中。抑制突触和非抑制突触的比例决定了加入全局同步振荡对方向选择性的影响。这些成分，短期压抑，空间收敛和伽马波段振荡，在感觉系统中无处不在，可以在reichardt式电路中用于生成和增强各种生物相关的时空计算。短期突触可塑性在脑回路中普遍存在，但其在感觉运动加工中的功能尚不清楚。我们提出了一个简约的运动处理模型，利用短期抑郁产生定向选择性反应。在模型电路中，来自两个空间上分离的感受野的信息经过突触的不对称处理后被组合在一起，这些突触要么表现出短期突触抑制，要么没有。在首选方向上的运动导致两个通道之间的建设性相互作用；相反方向的运动则不然。该模型将短期突触抑制描述为具有不同时间常数的两个过程。这个更快的过程本身就足以在电路中产生方向选择性。相反，缓慢的过程可以增强对持续刺激的方向选择性。因此，缓慢的过程介导了一种从警觉到辨别的注意力转移，在警觉状态下，神经元的反应更强烈，在辨别状态下，神经元的反应更有选择性，尖峰更少。这解释了先前观察到的在全球同步伽马波段振荡存在的情况下，弱电鱼的方向选择性增强。这些发现表明，伽马波段振荡和注意力之间存在着机制上的联系。
The discrimination of the direction of movement of sensory images is critical to the control of many animal behaviors. We propose a parsimonious model of motion processing that generates direction selective responses using short-term synaptic depression and can reproduce salient features of direction selectivity found in a population of neurons in the midbrain of the weakly electric fish Eigenmannia virescens. The model achieves direction selectivity with an elementary Reichardt motion detector: information from spatially separated receptive fields converges onto a neuron via dynamically different pathways. In the model, these differences arise from convergence of information through distinct synapses that either exhibit or do not exhibit short-term synaptic depression—short-term depression produces phase-advances relative to nondepressing synapses. Short-term depression is modeled using two state-variables, a fast process with a time constant on the order of tens to hundreds of milliseconds, and a slow process with a time constant on the order of seconds to tens of seconds. These processes correspond to naturally occurring time constants observed at synapses that exhibit short-term depression. Inclusion of the fast process is sufficient for the generation of temporal disparities that are necessary for direction selectivity in the elementary Reichardt circuit. The addition of the slow process can enhance direction selectivity over time for stimuli that are sustained for periods of seconds or more. Transient (i.e., short-duration) stimuli do not evoke the slow process and therefore do not elicit enhanced direction selectivity. The addition of a sustained global, synchronous oscillation in the gamma frequency range can, however, drive the slow process and enhance direction selectivity to transient stimuli. This enhancement effect does not, however, occur for all combinations of model parameters. The ratio of depressing and nondepressing synapses determines the effects of the addition of the global synchronous oscillation on direction selectivity. These ingredients, short-term depression, spatial convergence, and gamma-band oscillations, are ubiquitous in sensory systems and may be used in Reichardt-style circuits for the generation and enhancement of a variety of biologically relevant spatiotemporal computations. Short-term synaptic plasticity is ubiquitous in brain circuits, but its function in sensorimotor processing remains unclear. We propose a parsimonious model of motion processing using short-term depression to produce directionally selective responses. In the model circuit, information from two spatially separated receptive fields is combined after being asymmetrically processed by synapses that either exhibit short-term synaptic depression or do not. Motion in a preferred direction leads to a constructive interaction between the two channels; motion in the opposite direction does not. The model represents short-term synaptic depression as two processes with distinct time constants. The faster process alone suffices to generate direction selectivity in the circuit. The slow process, in contrast, can enhance direction selectivity to sustained stimuli. Therefore, the slow process mediates a form of attentional shift from alert, where the neuron responds more vigorously, to discriminating, where the neuron responds more selectively with fewer spikes. This explains a previously observed enhancement of direction selectivity in weakly electric fish in the presence of global synchronous gamma-band oscillations. These findings suggest a mechanistic connection between gamma-band oscillations and attention.
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影响因子：
2.9
作者：
Paninski, L;Pillow, JW;Simoncelli, EP
通讯作者：
Simoncelli, EP
影响因子：
5.3
作者：
Cowan, Noah J.;Fortune, Eric S.
通讯作者：
Fortune, Eric S.
影响因子：
7.8
作者：
Paninski, L
通讯作者：
Paninski, L
DOI：
10.1007/bf01352158
发表时间：
1973-01-01
期刊：
JOURNAL OF COMPARATIVE PHYSIOLOGY
影响因子：
--
作者：
HEILIGENBERG, W
通讯作者：
HEILIGENBERG, W
影响因子：
2.5
作者：
Ramcharitar, J. U.;Tan, E. W.;Fortune, E. S.
通讯作者：
Fortune, E. S.