Azizi S A, Woodward D J
Department of Neurology, Yale University, School of Medicine, New Haven, CT 06510.
Brain Res. 1990 Nov 19;533(2):255-62. doi: 10.1016/0006-8993(90)91347-j.
We have demonstrated previously that visual and auditory inputs reach the rat paraflocculus via dorsolateral pontine gray from the secondary regions of the visual and auditory cortices. It has also been demonstrated that mossy fiber responses can be evoked to physiological acoustic stimuli in unanesthetized preparations. In this study, we investigated the interaction of auditory and visual inputs in the paraflocculus. Activity of parafloccular neurons was recorded in immobilized, locally anesthetized hooded rats. Selected images and tones were presented to animals. Orientation, position, and velocity of visual stimuli and different parameters of acoustic stimuli were controlled by a computer. Visual and auditory stimuli were also presented in combination or in different temporal sequences. We discovered that visual and auditory stimuli have coextensive termination zones in paraflocculus, and influence the same neurons in 60% of the cases. Combined auditory and visual stimuli produced synergistic responses in parafloccular neurons in comparison with single modality stimuli. Augmentation of responses could be observed even when one of the stimuli was subthreshold and did not alter per se the neuronal activity. Our findings suggest that within the cerebro-cerebellar system, subthreshold inputs are capable of powerful control over the neuronal activity and may alter responses to subsequent stimuli when properly biased by inputs from paired modalities.
我们之前已经证明，视觉和听觉输入通过来自视觉和听觉皮层二级区域的背外侧脑桥灰质到达大鼠旁绒球。也有研究表明，在未麻醉的实验准备中，苔藓纤维反应可被生理声学刺激诱发。在本研究中，我们调查了旁绒球中听觉和视觉输入的相互作用。在固定、局部麻醉的有头罩大鼠中记录旁绒球神经元的活动。向动物呈现选定的图像和音调。视觉刺激的方向、位置和速度以及声学刺激的不同参数由计算机控制。视觉和听觉刺激也以组合或不同的时间顺序呈现。我们发现视觉和听觉刺激在旁绒球中有共同延伸的终止区，并且在60%的情况下影响相同的神经元。与单一模式刺激相比，听觉和视觉联合刺激在旁绒球神经元中产生协同反应。即使其中一个刺激低于阈值且本身不改变神经元活动，也能观察到反应增强。我们的研究结果表明，在脑-小脑系统中，阈下输入能够对神经元活动进行有力控制，并且当受到来自配对模式的输入适当偏向时，可能会改变对后续刺激的反应。
