Abstr. Assoc. Res. Otolaryngol. 23:177, 2000.

Formation of a map of ITD-tuned neurons in the barn owl's nucleus laminaris

R. Kempter, C. Leibold, J. L. van Hemmen, and H. Wagner

Computational maps are of central importance to the brain's representation of the outside world. The question of how maps are formed during ontogenetic development is a subject of intense research. The development in the primary visual cortex is in principle well explained compared to that in the auditory system, partly because the mechanisms underlying the formation of temporal-feature maps are hardly understood (Carr 1993, Ehret 1997, Buonomano & Merzenich 1998). Through a modelling study based on computer simulations in a system of spiking neurons we offer a solution to the problem of how a map of interaural time differences (ITDs) is set up in the nucleus laminaris of the barn owl, as a typical example. We show that an array of neurons is able to represent interaural time differences in an orderly manner, viz., a map, if homosynaptic spike-based Hebbian learning (Gerstner et al 1996, Markram et al 1997) is combined with a presynaptic propagation of synaptic modifications (Fitzsimonds & Poo 1998). The latter may be orders of magnitude weaker than the former. We argue that the algorithm is a key mechanism to the formation of temporal-feature maps on a submillisecond time scale.

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