2602 Production mechanism of columns with various shapes in formation of knowledge structure in hierarchical neural networks

Abstract

This chapter explores various models that have been devised for the development of columnar systems through local activity-dependent synaptic modification. The Von der Malsburg model is a classic example that is based on the proposition that mechanisms can be sufficient to account for experimental results. But such demonstrations alone do not provide tools to experimentally distinguish one mechanism from another. Recently, it is found that activity-dependent competitive mechanisms of synaptic plasticity appear to play an important role in many processes of late neural development, where an initially rough connectivity pattern refines to a precise, mature pattern. These processes may be modeled at several levels. Simple models use abstract neurons and assume synaptic modification according to a Hebbian or similar correlation-based rule. These models incorporate biological constraints and attempt to predict large-scale developmental patterns from the combination of synaptic-level plasticity rules and measurable biological patterns of activation and connectivity. More detailed models attempt to incorporate various levels of biophysical realism, including membrane and channel properties and dendritic geometry. Abstract models examine the connectivity patterns that may result if biological development follows certain dynamical or other abstract rules, without concern for how such rules might be implemented at the synapse.