P296 Spike timing dependent plasticity in the human parietal-prefrontal network

Abstract

Question Learning may occur through associative changes in the synaptic strength of neural connections that can be induced by coupling of activity of interconnected neurons with precise timing (spike-timing dependent plasticity, STDP). It is debated if this model can be applied in the context of large-scale cortical networks in humans. Methods We combined transcranial magnetic stimulation with concurrent electroencephalography to directly investigate if precise repeated activation of pre and post-synaptic large-scale cortical inputs produces STDP effects within the parietal-prefrontal network of 15 healthy volunteers. Results We found direct evidence for bidirectional STDP after effects over the DLPFC ruled by the PPC pre-synaptic inputs. Specifically, when the pre-synaptic input (PPC) precedes repeatedly the post-synaptic activation (DLPFC) by 10 ms a LTD-like effect of TMS-evoked activity is induced within the DLPFC. When the temporal order of the two stimulated areas is reverted, i.e. the pre-synaptic input (PPC) follows the post-synpatic input (DLPFC), we observed an LTP-like effect. Interestingly, such changes were accompained by PAS-depedendent modulations of the natural frequency of oscillation of the DLPFC, i.e. gamma activity. Conclusions We provide novel evidence that paired associative stimulation of posterior parietal cortex (PPC) and dorsolateral prefrontal cortex (DLPFC) induces bidirectional STDP effects in the post synaptic area (DLPFC) both in the time and in the time/frequency domain. Download : Download high-res image (811KB) Download : Download full-size image Download : Download high-res image (407KB) Download : Download full-size image