Receptive-field plasticity in the adult visual cortex: Dynamic signal rerouting or experience-dependent plasticity

Neurons in adult visual cortex can generate new receptive fields (RFs) when small retinal injuries remove their normal feedforward signals, a clear sign of plasticity. The activation of new RFs leads to a striking topographic map reorganization around the deafferentated cortical region. It appears that the lesion down-regulates GABAergic inhibition and uncovers the normally subthreshold signals from remote areas. The newly activated individual neurons and their assemblies show surprisingly normal response patterns, indicating that these large-scale alterations in the cortical map may contribute to, rather than disrupt, visual perception. Thus, weighing a variety of synaptic inputs based on the nature of the current drive and history of prior stimulation, the adult visual cortex is capable of showing considerable ''plasticity'' while maintaining the overall stability of its functional organization. In the mammalian visual system, however, the involvement of experience-dependent plasticity in this process is, as reviewed here, a matter of debate. (C) 1997 Academic Press.