Marrocco R T, McClurkin J W, Alkire M T
Institute of Neuroscience, University of Oregon, Eugene 97403-1254, USA.
Brain Res. 1996 Oct 21;737(1-2):110-8. doi: 10.1016/0006-8993(96)00660-9.
Previous studies of the cortical input to the mammalian dorsal lateral geniculate nucleus (LGN) have identified a number of possible functions for the corticogeniculate pathway, including alteration of LGN spatial frequency selectivity and facilitation of both binocular interactions and orientation selectivity. These changes may be due to either a tonic or a phasic cortical facilitation or both. The temporal differences between each of these inputs suggests that their impact on LGN cell temporal tuning should be unique. To test this hypothesis, we reversibly blocked the visual cortex (VI) and measured the effects on several indices of the temporal properties of LGN cells, including peak frequency, bandwidth, and response phase. Macaque monkeys were anesthetized and paralyzed during single cell recording from the LGN while area VI was cryogenically deactivated. Single-cell responses were visually evoked with drifting, luminance-modulated, sine-wave gratings and discrete-Fourier analyzed. Cortical cooling produced statistically significant increases or decreases in response amplitude in 64% of cells recorded. In most cases, alterations in response amplitude occurred for stimuli that varied in spatial as well as temporal frequency. For those cells influenced by changes in stimulus temporal frequency, the majority showed changes over a broad range of frequencies. A minority of cells showed changes in either peak temporal tuning or temporal frequency bandwidth. Response phase angles for all temporal frequencies tested were unaffected by cortical cooling. Overall, these results suggest that the cortical input may alter the temporal response properties of LGN cells, perhaps by tonic, but not exclusively excitatory, corticofugal influences.
以往对哺乳动物背外侧膝状核（LGN）皮质输入的研究已经确定了皮质膝状体通路的一些可能功能，包括改变LGN的空间频率选择性以及促进双眼相互作用和方向选择性。这些变化可能是由于持续性或阶段性的皮质促进作用，或者两者皆有。这些输入之间的时间差异表明，它们对LGN细胞时间调谐的影响应该是独特的。为了验证这一假设，我们可逆性地阻断了视觉皮层（V1），并测量了对LGN细胞时间特性的几个指标的影响，包括峰值频率、带宽和响应相位。在从LGN进行单细胞记录期间，对猕猴进行麻醉和麻痹，同时通过低温使V1区失活。用漂移的、亮度调制的正弦波光栅诱发单细胞反应，并进行离散傅里叶分析。在记录的64%的细胞中，皮质冷却使反应幅度产生了具有统计学意义的增加或减少。在大多数情况下，反应幅度的改变发生在空间频率和时间频率都不同的刺激下。对于那些受刺激时间频率变化影响的细胞，大多数细胞在很宽的频率范围内都有变化。少数细胞在峰值时间调谐或时间频率带宽方面有变化。所有测试时间频率的反应相位角不受皮质冷却的影响。总体而言，这些结果表明皮质输入可能会改变LGN细胞的时间反应特性，可能是通过持续性的，但并非完全是兴奋性的皮质离心影响。
