Chaplin Tristan A, Allitt Benjamin J, Hagan Maureen A, Price Nicholas S C, Rajan Ramesh, Rosa Marcello G P, Lui Leo L
Neuroscience Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, Australia; and.
ARC Centre of Excellence for Integrative Brain Function, Monash University Node, Victoria, Australia.
J Neurophysiol. 2017 Sep 1;118(3):1567-1580. doi: 10.1152/jn.00065.2017. Epub 2017 Jun 21.
Neurons in the middle temporal area (MT) of the primate cerebral cortex respond to moving visual stimuli. The sensitivity of MT neurons to motion signals can be characterized by using random-dot stimuli, in which the strength of the motion signal is manipulated by adding different levels of noise (elements that move in random directions). In macaques, this has allowed the calculation of "neurometric" thresholds. We characterized the responses of MT neurons in sufentanil/nitrous oxide-anesthetized marmoset monkeys, a species that has attracted considerable recent interest as an animal model for vision research. We found that MT neurons show a wide range of neurometric thresholds and that the responses of the most sensitive neurons could account for the behavioral performance of macaques and humans. We also investigated factors that contributed to the wide range of observed thresholds. The difference in firing rate between responses to motion in the preferred and null directions was the most effective predictor of neurometric threshold, whereas the direction tuning bandwidth had no correlation with the threshold. We also showed that it is possible to obtain reliable estimates of neurometric thresholds using stimuli that were not highly optimized for each neuron, as is often necessary when recording from large populations of neurons with different receptive field concurrently, as was the case in this study. These results demonstrate that marmoset MT shows an essential physiological similarity to macaque MT and suggest that its neurons are capable of representing motion signals that allow for comparable motion-in-noise judgments. We report the activity of neurons in marmoset MT in response to random-dot motion stimuli of varying coherence. The information carried by individual MT neurons was comparable to that of the macaque, and the maximum firing rates were a strong predictor of sensitivity. Our study provides key information regarding the neural basis of motion perception in the marmoset, a small primate species that is becoming increasingly popular as an experimental model.
灵长类动物大脑皮层颞中区（MT）的神经元对移动的视觉刺激有反应。MT神经元对运动信号的敏感性可以通过使用随机点刺激来表征，其中运动信号的强度通过添加不同水平的噪声（沿随机方向移动的元素）来操纵。在猕猴中，这使得能够计算“神经测量”阈值。我们表征了在舒芬太尼/一氧化二氮麻醉的狨猴中MT神经元的反应，狨猴作为视觉研究的动物模型最近引起了相当大的关注。我们发现MT神经元表现出广泛的神经测量阈值，并且最敏感神经元的反应可以解释猕猴和人类的行为表现。我们还研究了导致观察到的阈值范围广泛的因素。对首选方向和零方向运动反应的放电率差异是神经测量阈值最有效的预测指标，而方向调谐带宽与阈值无关。我们还表明，使用对每个神经元没有高度优化的刺激也可以获得可靠的神经测量阈值估计，就像本研究中同时记录具有不同感受野的大量神经元时经常需要的那样。这些结果表明，狨猴MT与猕猴MT表现出基本的生理相似性，并表明其神经元能够代表运动信号，从而做出类似的噪声中的运动判断。我们报告了狨猴MT神经元对不同相干性的随机点运动刺激的反应。单个MT神经元携带的信息与猕猴的相当，最大放电率是敏感性的有力预测指标。我们的研究提供了关于狨猴运动感知神经基础的关键信息，狨猴是一种小型灵长类动物，正日益成为一种流行的实验模型。
