Sleep-like slow oscillations improve image classification through synaptic homeostasis and memory association in a thalamo-cortical model
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The occurrence of sleep passed through the evolutionary sieve and is widespread in animal species. Sleep is known to be beneficial to cognitive and mnemonic tasks, while chronic sleep deprivation is detrimental. Despite the importance of the phenomenon, a theoretical and computational approach demonstrating the underlying mechanisms is still lacking. In this paper, we show interesting effects of deep-sleep-like slow oscillation activity on a simplified thalamo-cortical model which is trained to encode, retrieve and classify images of handwritten digits. During slow oscillations, spike-timing-dependent-plasticity (STDP) produces a differential homeostatic process. It is characterized by both a specific unsupervised enhancement of connections among groups of neurons associated to instances of the same class (digit) and a simultaneous down-regulation of stronger synapses created by the training. This is reflected in a hierarchical organization of post-sleep internal representations. Such effects favour higher performances in retrieval and classification tasks and create hierarchies of categories in integrated representations. The model leverages on the interaction between of top-down cortico-thalamic predictions and bottom-up thalamo-cortical projections during deep-sleep-like slow oscillations. Such mechanism hints at possible applications to artificial learning systems.
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