Cosyne 2008 Workshops
March 4, 2008
Snow Bird, Utah
Joshua Young
STDP and the didactic reorganization of cortical response properties
It has long been assumed that, in mature animals, neurons involved in fundamental perceptual processing are fixed in their connectivity and their resulting function. This paradigm has been shaken in recent years by numerous demonstrations of high levels of functional plasticity among such neurons, long after development is complete. Cortical neurons that undergo a substantial loss of synaptic input enter a transient phase of hyperactivity that is associated with a decrease in response selectivity. Over a longer time period activity levels are reduced and selectivity returns, often accompanied by modified stimulus preferences. We have recently described a new plasticity phenomenon in primary visual cortex, where neurons that are separated by large distances show a remarkable degree of coordination in the spatial reorganization of their receptive fields. These coordinated receptive field changes are highly consistent with the hypothesis that the long-term organization of neuronal connectivity is spike timing-dependent. The results are also highly inconsistent with the hypothesis that the organization is correlation-dependent plasticity. Of particular interest is that these coordinated receptive field changes appear to arise from a previously unobserved interaction between spike timing-dependent plasticity and the balance of excitation and inhibition within a network, which allows neurons to ‘teach’ their stimulus preferences to other neurons, even neurons to which they are not directly (i.e. monosynaptically) connected. Fundamental to this process, referred to as didactic reorganization, is an intra-network competition for the control of spike timing.
