Weyand T G, Gafka A C
Department of Cell Biology and Anatomy, LSU Medical Center, New Orleans 70112, USA.
Vis Neurosci. 1998 Jan-Feb;15(1):123-40. doi: 10.1017/s0952523898151088.
We studied the visuomotor properties of 645 neurons in area 6 of five cats trained in oculomotor tasks. The area we recorded from corresponds well with territories believed to contain the feline homologue of the frontal eye fields observed in primates. Despite an expectation that cells with pre-saccadic activity would be common, only a small fraction (approximately 5%) of the cells displayed activity that could be linked to subsequent saccadic eye movements. These pre-motor cells appeared to be distributed over a broad region of cortex mixed in with other cell types. As in primates, saccade-related activity tended to occur only during "purposeful" saccades. At least 30% (208/645) of the neurons were visual, with many of these cells possessing huge receptive fields that appeared to include the entire contralateral visual field. Visual responsiveness was generally attenuated by fixation during the oculomotor tasks. Although attentional mechanisms may play a role in this attenuation, this cortical area also exhibits powerful lateral interactions in which spatially displaced visual stimuli suppress each other. Most cells, visually responsive or not, were affected by fixation. Nearly equal proportions of cells showed increases or decreases in activity during fixation. For many of the cells affected by fixation, the source of this modulation appears to reflect cognitive, rather than sensory or motor processes. This included cells that showed anticipatory activity, and cells that responded to the reward only when it was presented in the context of the task. Based on the paucity of pre-saccadic neurons, it would be difficult to conclude that this region of cortex in the cat is homologous to the frontal eye fields of the monkey. However, when considered in the context of differences in the oculomotor habits of these two animals, we believe the homology fits. In addition to pre-motor neurons, the properties of several other cell types found in this area could contribute to the control of gaze.
我们研究了五只经眼动任务训练的猫的645个位于6区的神经元的视觉运动特性。我们记录的区域与被认为包含在灵长类动物中观察到的额叶眼区的猫科动物同源区域非常吻合。尽管预期具有扫视前活动的细胞会很常见，但只有一小部分（约5%）的细胞表现出与随后的眼球扫视运动相关的活动。这些运动前细胞似乎分布在广泛的皮质区域，与其他细胞类型混合在一起。与灵长类动物一样，与扫视相关的活动往往只在“有目的的”扫视期间出现。至少30%（208/645）的神经元具有视觉功能，其中许多细胞拥有巨大的感受野，似乎包括整个对侧视野。视觉反应性在眼动任务期间通常会因注视而减弱。虽然注意力机制可能在这种减弱中起作用，但这个皮质区域也表现出强大的侧向相互作用，其中空间上移位的视觉刺激相互抑制。大多数细胞，无论是否具有视觉反应性，都受到注视的影响。在注视期间，细胞活动增加或减少的比例几乎相等。对于许多受注视影响的细胞，这种调节的来源似乎反映了认知过程，而不是感觉或运动过程。这包括表现出预期活动的细胞，以及仅在任务背景下出现奖励时才做出反应的细胞。基于扫视前神经元的稀少，很难得出猫的这个皮质区域与猴子的额叶眼区同源的结论。然而，考虑到这两种动物眼动习惯的差异，我们认为这种同源性是合理的。除了运动前神经元外，在这个区域发现的其他几种细胞类型的特性也可能有助于控制注视。
