Ebitz R Becket, Moore Tirin
Department of Neurobiology and
Department of Neurobiology and.
J Neurosci. 2017 May 10;37(19):5008-5018. doi: 10.1523/JNEUROSCI.2433-16.2017. Epub 2017 Apr 21.
The prefrontal cortex (PFC) is thought to flexibly regulate sensorimotor responses, perhaps through modulating activity in other circuits. However, the scope of that control remains unknown: it remains unclear whether the PFC can modulate basic reflexes. One canonical example of a central reflex is the pupil light reflex (PLR): the automatic constriction of the pupil in response to luminance increments. Unlike pupil size, which depends on the interaction of multiple physiological and neuromodulatory influences, the PLR reflects the action of a simple brainstem circuit. However, emerging behavioral evidence suggests that the PLR may be modulated by cognitive processes. Although the neural basis of these modulations remains unknown, one possible source is the PFC, particularly the frontal eye field (FEF), an area of the PFC implicated in the control of attention. We show that microstimulation of the rhesus macaque FEF alters the magnitude of the PLR in a spatially specific manner. FEF microstimulation enhanced the PLR to probes presented within the stimulated visual field, but suppressed the PLR to probes at nonoverlapping locations. The spatial specificity of this effect parallels the effect of FEF stimulation on attention and suggests that FEF is capable of modulating visuomotor transformations performed at a lower level than was previously known. These results provide evidence of the selective regulation of a basic brainstem reflex by the PFC. The pupil light reflex (PLR) is our brain's first and most fundamental mechanism for light adaptation. Although it is often described in textbooks as being an immutable reflex, converging evidence suggests that the magnitude of the PLR is modulated by cognitive factors. The neural bases of these modulations are unknown. Here, we report that microstimulation in the prefrontal cortex (PFC) modulates the gain of the PLR, changing how a simple reflex circuit responds to physically identical stimuli. These results suggest that control structures such as the PFC can add complexity and flexibility to even a basic brainstem circuit.
前额叶皮质（PFC）被认为可以灵活地调节感觉运动反应，或许是通过调节其他神经回路的活动来实现。然而，这种控制的范围仍然未知：目前尚不清楚PFC是否能够调节基本反射。中枢反射的一个典型例子是瞳孔对光反射（PLR）：即瞳孔对亮度增加做出的自动收缩反应。与取决于多种生理和神经调节影响相互作用的瞳孔大小不同，PLR反映的是一个简单脑干回路的作用。然而，新出现的行为证据表明，PLR可能会受到认知过程的调节。尽管这些调节的神经基础仍然未知，但一个可能的来源是PFC，特别是额叶眼区（FEF），这是PFC中与注意力控制有关的一个区域。我们发现，对恒河猴FEF进行微刺激会以空间特异性的方式改变PLR的幅度。FEF微刺激增强了对刺激视野内呈现的探测刺激的PLR，但抑制了对非重叠位置探测刺激的PLR。这种效应的空间特异性与FEF刺激对注意力的影响相似，表明FEF能够调节比之前所知更低水平的视觉运动转换。这些结果为PFC对基本脑干反射的选择性调节提供了证据。瞳孔对光反射（PLR）是我们大脑中光适应的首要且最基本的机制。尽管它在教科书中常被描述为一种不变的反射，但越来越多的证据表明，PLR的幅度会受到认知因素的调节。这些调节的神经基础尚不清楚。在此，我们报告前额叶皮质（PFC）中的微刺激会调节PLR的增益，改变一个简单反射回路对物理上相同刺激的反应方式。这些结果表明，诸如PFC这样的控制结构甚至可以给一个基本的脑干回路增加复杂性和灵活性。
