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猴脑顶盖网状神经元的放电特性

Discharge properties of monkey tectoreticular neurons.

作者信息

Rodgers C Kip, Munoz Douglas P, Scott Stephen H, Paré Martin

机构信息

Canadian Institutes of Health Research Group in Sensory-Motor Systems and Centre for Neuroscience Studies, Ontario, Canada.

出版信息

J Neurophysiol. 2006 Jun;95(6):3502-11. doi: 10.1152/jn.00908.2005. Epub 2006 Apr 26.

Abstract

The intermediate layers of the superior colliculus (SC) contain neurons that clearly play a major role in regulating the production of saccadic eye movements: a burst of activity from saccade neurons (SNs) is thought to provide a drive signal to set the eyes in motion, whereas the tonic activity of fixation neurons (FNs) is thought to suppress saccades during fixation. The exact contribution of these neurons to saccade control is, however, unclear because the nature of the signals sent by the SC to the brain stem saccade generation circuit has not been studied in detail. Here we tested the hypothesis that the SC output signal is sufficient to control saccades by examining whether antidromically identified tectoreticular neurons (TRNs: 33 SNs and 13 FNs) determine the end of saccades. First, TRNs had discharge properties similar to those of nonidentified SC neurons and a proportion of output SNs had visually evoked responses, which signify that the saccade generator must receive and process visual information. Second, only a minority of TRNs possessed the temporal patterns of activity sufficient to terminate saccades: Output SNs did not cease discharging at the time of saccade end, possibly continuing to drive the brain stem during postsaccadic fixations, and output FNs did not resume their activity before saccade end. These results argue against a role for SC in regulating the timing of saccade termination by a temporal code and suggest that other saccade centers act to thwart the extraneous SC drive signal, unless it controls saccade termination by a spatial code.

摘要

上丘(SC)的中间层包含一些神经元,它们在调节眼球扫视运动的产生中显然起着主要作用:扫视神经元(SNs)的一阵活动被认为提供了一个驱动信号,使眼睛开始运动,而注视神经元(FNs)的紧张性活动被认为在注视期间抑制扫视。然而,这些神经元对扫视控制的确切贡献尚不清楚,因为上丘向脑干扫视生成回路发送的信号的性质尚未得到详细研究。在这里,我们通过检查经逆向鉴定的顶盖网状神经元(TRNs:33个SNs和13个FNs)是否决定扫视的结束,来测试上丘输出信号足以控制扫视的假设。首先,TRNs具有与未鉴定的上丘神经元相似的放电特性,并且一部分输出SNs具有视觉诱发反应,这表明扫视发生器必须接收和处理视觉信息。其次,只有少数TRNs具有足以终止扫视的活动时间模式:输出SNs在扫视结束时并未停止放电,可能在扫视后注视期间继续驱动脑干,并且输出FNs在扫视结束前并未恢复其活动。这些结果反对上丘通过时间编码调节扫视终止时间的作用,并表明其他扫视中枢会阻止多余的上丘驱动信号,除非它通过空间编码控制扫视终止。

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