Ozeki Hirofumi, Finn Ian M, Schaffer Evan S, Miller Kenneth D, Ferster David
Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA.
Neuron. 2009 May 28;62(4):578-92. doi: 10.1016/j.neuron.2009.03.028.
In what regime does the cortical circuit operate? Our intracellular studies of surround suppression in cat primary visual cortex (V1) provide strong evidence on this question. Although suppression has been thought to arise from an increase in lateral inhibition, we find that the inhibition that cells receive is reduced, not increased, by a surround stimulus. Instead, suppression is mediated by a withdrawal of excitation. Thalamic recordings and previous work show that these effects cannot be explained by a withdrawal of thalamic input. We find in theoretical work that this behavior can only arise if V1 operates as an inhibition-stabilized network (ISN), in which excitatory recurrence alone is strong enough to destabilize visual responses but feedback inhibition maintains stability. We confirm two strong tests of this scenario experimentally and show through simulation that observed cell-to-cell variability in surround effects, from facilitation to suppression, can arise naturally from variability in the ISN.
皮质回路在何种机制下运行？我们对猫初级视觉皮层（V1）周围抑制的细胞内研究为这个问题提供了有力证据。尽管一直认为抑制是由侧向抑制的增加引起的，但我们发现，周围刺激会使细胞接收到的抑制减少而非增加。相反，抑制是由兴奋的撤回介导的。丘脑记录和先前的研究表明，这些效应无法用丘脑输入的撤回来解释。我们在理论研究中发现，只有当V1作为一个抑制稳定网络（ISN）运行时，这种行为才会出现，在该网络中，仅兴奋性循环就足以使视觉反应不稳定，但反馈抑制维持稳定性。我们通过实验证实了对这种情况的两个有力测试，并通过模拟表明，从易化到抑制的周围效应中观察到的细胞间变异性可以自然地源于ISN中的变异性。
