Cromer Jason A, Waitzman David M
University of Connecticut Health Center, Department of Neurology, MC 3974, 263 Farmington Avenue, Farmington, CT 06030, USA.
J Physiol. 2006 Feb 1;570(Pt 3):507-23. doi: 10.1113/jphysiol.2005.096834. Epub 2005 Nov 24.
Neurones in the central mesencephalic reticular formation (cMRF) begin to discharge prior to saccades. These long lead burst neurones interact with major oculomotor centres including the superior colliculus (SC) and the paramedian pontine reticular formation (PPRF). Three different functions have been proposed for neurones in the cMRF: (1) to carry eye velocity signals that provide efference copy information to the SC (feedback), (2) to provide duration signals from the omnipause neurones to the SC (feedback), or (3) to participate in the transformation from the spatial encoding of a target selection signal in the SC into the temporal pattern of discharge used to drive the excitatory burst neurones in the pons (feed-forward). According to each respective proposal, specific predictions about cMRF neuronal discharge have been formulated. Individual neurones should: (1) encode instantaneous eye velocity, (2) burst specifically in relation to saccade duration but not to other saccade metrics, or (3) have a spectrum of weak to strong correlations to saccade dynamics. To determine if cMRF neurones could subserve these multiple oculomotor roles, we examined neuronal activity in relation to a variety of saccade metrics including amplitude, velocity and duration. We found separate groups of cMRF neurones that have the characteristics predicted by each of the proposed models. We also identified a number of subgroups for which no specific model prediction had previously been established. We found that we could accurately predict the neuronal firing pattern during one type of saccade behaviour (visually guided) using the activity during an alternative behaviour with different saccade metrics (memory guided saccades). We suggest that this evidence of a close relationship of cMRF neuronal discharge to individual saccade metrics supports the hypothesis that the cMRF participates in multiple saccade control pathways carrying saccade amplitude, velocity and duration information within the brainstem.
中脑中央网状结构（cMRF）中的神经元在扫视之前就开始放电。这些长潜伏期爆发神经元与包括上丘（SC）和脑桥旁正中网状结构（PPRF）在内的主要动眼神经中枢相互作用。对于cMRF中的神经元，已经提出了三种不同的功能：（1）携带眼速度信号，为SC提供传出副本信息（反馈）；（2）从全暂停神经元向SC提供持续时间信号（反馈）；或者（3）参与从SC中目标选择信号的空间编码到用于驱动脑桥中兴奋性爆发神经元的放电时间模式的转换（前馈）。根据各自的提议，已经对cMRF神经元放电做出了具体预测。单个神经元应该：（1）编码瞬时眼速度；（2）特别是与扫视持续时间相关而不是与其他扫视指标相关地爆发；或者（3）与扫视动力学具有从弱到强的一系列相关性。为了确定cMRF神经元是否可以承担这些多种动眼神经作用，我们研究了与包括幅度、速度和持续时间在内的各种扫视指标相关的神经元活动。我们发现了cMRF神经元的不同组，它们具有每个提议模型所预测的特征。我们还确定了一些以前没有建立具体模型预测的亚组。我们发现，我们可以使用具有不同扫视指标的另一种行为（记忆引导扫视）期间的活动，准确预测一种扫视行为（视觉引导）期间的神经元放电模式。我们认为，cMRF神经元放电与单个扫视指标密切相关的这一证据支持了以下假设：cMRF参与了脑干内携带扫视幅度、速度和持续时间信息的多种扫视控制途径。
