Pattern matching in a model of dendritic spines.
Pattern matching, the ability to recognize and maximally respond to an input pattern that is similar to a previously learned pattern, is an essential step in any learning process. To investigate the properties of pattern matching in biological neurons, and in particular the role of a calcium-dependent potassium conductance, a circuit model of a small area of dendritic membrane with a number of dendritic spines is developed. Circuit model simulations show that dendritic membrane depolarization is greater in response to a previously learned pattern of synaptic inputs than in response to a novel pattern of synaptic inputs. These simulations, in combination with an analysis of the circuit model equations, reveal that when a synaptic input pattern is similar to the learned pattern of synaptic inputs, the total dendritic depolarization is a linear combination of dendritic depolarization contributed by individual spines. When at least one synaptic input differs markedly from the learned value, dendritic depolarization is a nonlinear combination of individual spine depolarizations. These principles of spine interactions are captured in a computationally simple set of 'similarity measure' equations which are shown to reproduce the response surface of the circuit model output. Thus, these similarity measure equations not only describe a biologically plausible model of pattern matching, they also satisfy computational requirements for use in artificial neural networks.
Blackwell
K T
KT
Environmental Research Institute of Michigan, Arlington, VA 22209, USA.
Vogl
T P
TP
Alkon
D L
DL
D000818:Animals; D003198:Computer Simulation; D003712:Dendrites / Q000502:physiology*; D006801:Humans; D007425:Intracellular Membranes / Q000502:physiology; D008959:Models, Neurological; D009431:Neural Conduction / Q000502:physiology; D010363:Pattern Recognition, Automated; D013569:Synapses / Q000502:physiology