从不平衡的视觉输入到不平衡的视觉注意:探寻短时程眼优势可塑性的神经机制

From imbalanced visual inputs to imbalanced visual attention:Seeking the neural mechanisms for short-term ocular dominance plasticity

在个体视觉系统的发展过程中,视觉系统的结构与功能会受到视觉经验和内外部环境的影响而发生改变,这被称为视觉可塑性。视觉可塑性在出生后的发育关键期内达到峰值。虽然成年期视皮层神经环路的结构功能趋于稳定,但有越来越多的研究表明成年人视皮层中仍保留着一定程度的可塑性,其中的典型代表就是眼优势的可塑性。最近十几年的研究发现,短时程操控成年人的各种视觉输入信息,乃至调节两眼间注意资源的分配,都可以引起成年人眼优势发生偏移。然而,两者调节眼优势的神经机制可能并不相同。视觉输入对成年人眼优势的调节可能主要反映了视觉皮层的稳态可塑性机制;而注意对眼优势的影响则是一种高级加工对初级视觉皮层的反馈调节,目前可以用拮抗神经元的适应机制来作解释。未来研究可以寻找更加直接的证据来支持这一解释,此外也应重点关注注意与视觉输入之间会如何交互影响成年人眼优势。

During the development,the structure and functions of the visual system can be affected by visual experiences and environments.This is called visual plasticity which is most prominent during the critical period of development after birth.Although the structures and functions of neural circuits tend to be stable in adult visual cortex,mounting evidence has shown that adult visual cortex still retains a certain degree of plasticity,including ocular dominance plasticity.In recent decades,it has been found that perceptual ocular dominance in adults can be biased by adjusting the input information or attentional allocation between the two eyes.However,the neural mechanisms underlying these different types of ocular dominance plasticity may have multiple origins.Monocular deprivation due to imbalanced visual inputs may be accounted for by the homeostatic plasticity mechanism of the visual cortex.However,the shift of ocular dominance caused by imbalanced attentional allocations between the two eyes reflects the feedbacks from higher cortical sites,which is currently explained by the adaptation of ocular opponency neurons.Future studies may provide more direct evidence for the ocular-opponency-neuron account and explore the likely interactions between attention and visual input that reshape ocular dominance.