Heggelund P, Karlsen H E, Flugsrud G, Nordtug T
Institute of Neurophysiology, University of Oslo, Norway.
Exp Brain Res. 1989;74(1):116-30. doi: 10.1007/BF00248285.
We recorded the response of sustained (X) and transient (Y) cells in the cat lateral geniculate nucleus (LGN) and optic tract to a stationary spot while the spot luminance was increased and decreased with a constant rate (linear luminance functions), or modulated sinusoidally. The spot filled the receptive field center, and was surrounded by an annulus of fixed luminance. The LGN X cells seemed to perform a differentiation-like operation in the time domain at slow temporal modulations, giving information about rate of luminance change. To the linear luminance functions the cells responded with a constant firing rate. The on-center cells were activated during increasing luminance, the off-center cells during decreasing luminance. This firing rate increased monotonically with rate of luminance change. To low-frequency sinusoidal modulations the cells had a marked negative phase shift. The response of the LGN Y cells had a transient component shortly after the luminance started to increase (on-center cells) or decrease (off-center cells), followed by a secondary, gradually changing component. The peak of the transient component occurred on average when the response of the X cells increased most rapidly. To low-frequency sinusoidal modulation the average negative phase shift of this peak was twice the average of the X cells. The Y system could accordingly provide information about rate of change in the response of the X system. In the optic tract the X fiber response resembled the LGN X cell response in most respects. The Y fibers had only a weak transient response component, so this component was accentuated in the thalamic relay. Also the sensitivity for rate of luminance change was increased in LGN.
我们记录了猫外侧膝状体核（LGN）和视束中持续型（X）细胞和瞬变型（Y）细胞对一个静止光斑的反应，同时光斑亮度以恒定速率增加和降低（线性亮度函数），或进行正弦调制。光斑充满感受野中心，并被固定亮度的环形区域包围。在缓慢的时间调制下，LGN的X细胞似乎在时域中执行类似微分的操作，给出有关亮度变化率的信息。对于线性亮度函数，细胞以恒定的放电率做出反应。中心兴奋型细胞在亮度增加时被激活，中心抑制型细胞在亮度降低时被激活。这种放电率随亮度变化率单调增加。对于低频正弦调制，细胞有明显的负相位偏移。LGN的Y细胞的反应在亮度开始增加（中心兴奋型细胞）或降低（中心抑制型细胞）后不久有一个瞬态成分，随后是一个二次的、逐渐变化的成分。瞬态成分的峰值平均出现在X细胞反应增加最快的时候。对于低频正弦调制，这个峰值的平均负相位偏移是X细胞平均值的两倍。因此，Y系统可以提供有关X系统反应变化率的信息。在视束中，X纤维的反应在大多数方面类似于LGN的X细胞反应。Y纤维只有一个微弱的瞬态反应成分，所以这个成分在丘脑中继中被增强。LGN对亮度变化率的敏感性也增加了。
