Background: Long-term potentiation (LTP) is the best characterized form of synaptic plasticity. Animal studies suggest that LTP is a central mechanism in learning, memory, and psychiatric illnesses. Despite these findings, there is a paucity of human LTP studies. The scarcity of human research is mainly due to a lack of methods for non-invasive measurements of LTP-like plasticity in the brain. However, plasticity of the visual evoked potential (VEP) has in recent years emerged as a promising non-invasive method for assessment of LTP-like plasticity in the human cortex. The method ́s robustness and the effects of age, gender, and time-of-day on plasticity of the VEP remain to be clarified. Objectives: The present study had two main aims. First, we aimed to replicate VEP plasticity in the largest sample of healthy volunteers to date. Second, we aimed to assess the effects of age, gender, and time-of-day on plasticity of the VEP. Method: 119 healthy human control subjects between the ages of 18-65 were recruited to participate. VEP`s were elicited by checkerboard reversal stimulation before and after a modulation block of prolonged (10 mins) visual stimulation. Plasticity of the VEP was assessed by computing changes in C1, P1, N1 and P1-N1 peak-to peak amplitudes from pre- to post-modulation. Results: The modulation block induced significant changes in VEP amplitudes with the following p-values and effect sizes (Cohen`s d): C1 (p < .001, d = .56), P1 (p < .001, d = .42), N1 (p = 0.002, d = .30), and P1-N1 (p < .001, d = .58) peak-to-peak measures. There were significant effects of age, gender, and time-of-day on pre-modulation VEP amplitudes and latencies. There were no significant effects of age, gender, and time-of-day on plasticity of the VEP. Conclusion: We confirmed plasticity of the VEP in the largest sample of humans to date. There were significant effects of age, gender, and time-of-day on pre-modulation VEP`s, but not on plasticity of the VEP. Together, these findings indicate that VEP plasticity is a robust and accessible method for non-invasive studies of LTP-like cortical synaptic processes in humans.