en Experimental research article Experimental research article <p>  The effectiveness of θ pattern primed-bursts (PBs) on development of primed-burst (PB) potentiation was investigated in layer II/III of the adult rat visual cortex in vitro. Experiments were carried out in the visual cortical slices. Population excitatory post-synaptic potentials (pEPSPs) were evoked in layer II/III by stimulation of either white mater or layer IV. To induce long-term potentiation (LTP), eight episodes of PBs were delivered at 0.1 Hz. Regardless of stimulation site, field potential recorded in layer II/III consisted of two components: a short latency and high amplitude response called pEPSP₁, and a long latency and low amplitude response called pEPSP₂. The incidence of LTP produced by PBs of layer IV was higher than that of the white mater tetanization. In contrast, PBs of both layer IV and white mater reliably induced LTP of pEPSP₂ in layer II/III. It is concluded that PBs, as a type of activity pattern, of either white mater or layer IV can gain access to the modifiable synapses that are related to pEPSP₂ in layer II/III, but accessibility of the modifiable synapses that are related to pEPSP₁ depends on tetanization site. Relevancy of the results to the plasticity gate hypothesis is also discussed. </p><p>  </p> Primed-burst stimulation; Long term potentiation; Visual cortex; Layer IV; White mater 17 24 http://ppj.phypha.ir/browse.php?a_code=A-10-66-2&slc_lang=en&sid=1 Mahmood Salami 320031947532846001846 320031947532846001846 Yes Yaghub Fathollahi 320031947532846001847 320031947532846001847 No Fereshteh Motamedi 320031947532846001848 320031947532846001848 No Hossein Esteky 320031947532846001849 320031947532846001849 No