Abstract
The structural organization of cortical areas is not random, with topographic maps commonplace in sensory processing centers. This topographical organization allows optimal wiring between neurons, multimodal sensory integration, and performs input dimensionality reduction. In this work, a model of topographic map formation is implemented on the SpiNNaker neuromorphic platform, running in realtime using point neurons, and making use of both synaptic rewiring and spike-timing dependent plasticity (STDP). In agreement with Bamford et al. (2010), we demonstrate that synaptic rewiring refines an initially rough topographic map over and beyond the ability of STDP, and that input selectivity learnt through STDP is embedded into the network connectivity through rewiring. Moreover, we show the presented model can be used to generate topographic maps between layers of neurons with minimal initial connectivity, and stabilize mappings which would otherwise be unstable through the inclusion of lateral inhibition.
Highlights
Ramón y Cajal postulated that: “In the adult centers, the nerve paths are something fixed, ended, and immutable
The current section is concerned with providing an overview of the SpiNNaker structural plasticity framework that was created in order to facilitate the implementation of the model of synaptic rewiring proposed by Bamford et al (2010)
Self-connections provide the neuron with no extra information, which is potentially a reason why they are avoided in brains from leeches to mammalians (Grueber and Sagasti, 2010)
Summary
Ramón y Cajal postulated that: “In the adult centers, the nerve paths are something fixed, ended, and immutable. Everything may die, nothing may be regenerated” (Ramón y Cajal, 1928). Mammalian brains change their connectivity from early development and throughout adulthood. The neuromuscular junction sees neural competition for the innervation of muscle fibres resulting in their receiving inputs from single motoneurons (Buffelli et al, 2004; Favero et al, 2010). Brains undergo a period of over-growth of synapses which is maintained until puberty when massive synaptic pruning occurs (Zecevic and Rakic, 1991)
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