Alterations in brain connectivity due to plasticity and synaptic delay

Brain plasticity refers to brain's ability to change neuronal connections, as a result of environmental stimuli, new experiences, or damage. In this work, we study the effects of the synaptic delay on both the coupling strengths and synchronization in a neuronal network with synaptic plasticity. We build a network of Hodgkin-Huxley neurons, where the plasticity is given by the Hebbian rules. We verify that without time delay the synapses become regulated by both the nature (excitatory or inhibitory) and the frequency of the presynaptic and postsynaptic neuron. A presynaptic excitatory (inhibitory) neuron with higher (lower) frequency enhances the synaptic strength if the postsynaptic excitatory (inhibitory) neuron has lower (higher) frequency. When the delay is increased the network presents a non-trivial topology. Regarding the synchronization, only for small values of the synaptic delay this phenomenon is observed.