Activity-dependent regulation of receptive field properties of cat area 17by supervised Hebbian learning

Most algorithms currently used to model synaptic plasticity in self-organiz ing cortical networks suppose that the change in synaptic efficacy is gover ned by the same structuring factor, i.e., the temporal correlation of activ ity between pre- and postsynaptic neurons. Functional predictions generated by such algorithms have been tested electrophysiologically in the visual c ortex of anesthetized and paralyzed cats, Supervised learning procedures we re applied at the cellular level to change receptive field (RF) properties during the time of recording of an individual functionally identified cell. The protocols were devised as cellular analogs of the plasticity of RF pro perties, which is normally expressed during a critical period of postnatal development. We summarize here evidence demonstrating that changes in covar iance between afferent input and postsynaptic response imposed during extra cellular and intracellular conditioning can acutely induce selective long-l asting up- and down-regulations of visual responses. The functional propert ies that could be modified in 40% of cells submitted to differential pairin g protocols include ocular dominance, orientation selectivity and orientati on preference, interocular orientation disparity, and the relative dominanc e of ON and OFF responses. Since changes in RF properties can be induced in the adult as well, our findings also suggest that similar activity-depende nt processes mag occur during development and during active phases of learn ing under the supervision of behavioral attention or contextual signals. Su ch potential for plasticity in primary visual cortical neurons suggests the existence of a hidden connectivity expressing a wider functional competenc e than the one revealed at the spiking level. In particular, in the spatial domain the sensory synaptic integration field is larger than the classical discharge field. It can be shaped by supervised learning and its subthresh old extent can be unmasked by the pharmacological blockade of intracortical inhibition. (C) 1999 John Wiley & Sons, Inc.