Study On Features Of Local Field Potential Oscillation In Primary Visual Cortex Of Rats In Different Stages Of Development

ObjectiveWe study the laminar feature of local field potential in primary visual cortex (V1) of rat in different stages of development, in order to investigate the laminar processing mechanism in V1functional columns and the role of intracortical inhibition in the critical periods and visual plasticity.MethodsWith extracellular recording techniques, we tested the spontaneous local field potential in the primary visual cortex of rat in different stages of development under anesthesia. Power spectrums are got via fast Fourier transformation (FFT) of local field oscillation. We analyzed Power of low frequency (2-5Hz) and high frequency (10-20Hz) in layer2/3and layer5of each group. The scatterplot figures of Power Ration and cortical depth were drawn in3groups, defined as Power Ratio=(P high+Plow)/(P high-Plow)(Phigh and Plow represent the Power in the5-10Hz and10-20Hz ranges, respectively). Powers of10-20Hz band and Power Ratio in layer5were compared among3groups. Laminar features of local field oscillation of V1in different stages of development were investigated.ResultsThe feature of local field oscillation in V1of P14-16rats:For many recording sites, there were prominent peaks at2-5Hz. Otherwise, the Power spectrum of spontaneous activity showed a prominent peak at10-20Hz in layer5, apart from low-frequency activity. Power Ratio is positively correlated with cortical depth which is estimated from distance traveled by electrode. The correlation is highly significant (P=0.007).The regression equation were y=-1.293+0.001x (r=0.527, P=0.007).The feature of local field oscillation in V1of P20-22rats:unlike P14-16rat,there is no difference between layer2/3and layer5.The main Power is at low-frequency range. The correlation between Power Ratio and depth is insignificantly (P=0.733).Interestingly, adult rats represented high similarity to P14-16rat. Analyses of the Power in layer2/3and layer5indicates that a prominent peak exists at10-20Hz. Power Ratio is significantly correlated with cortical depth. The regression equation were y=-0.649+0.001x (r=0.663, P=0.0.00)By comparing Power values in layer5and Power Ratio among3groups, we found there was no significant difference in the power of spontaneous oscillation between P14-16rats and P60rats (P=0.551). Neither is the Power Ratio.However, for Power and Power Ratio, P20-22rats are significantly different from other two groups (P=0.000).ConclusionsThe spontaneous local field potentials in V1of rats were observed, we mainly focus on the laminar feature. We found that laminar feature varies from ages. In early childhood and adult rat, the local field oscillation in V1shows laminar specificity. For many recording sites in layer2/3, there were prominent peaks at2-5Hz. Otherwise, the Power spectrum of spontaneous activity showed a prominent peak at10-20Hz in layer5, apart from low-frequency activity. In childhood rats, such phenomenon havn’t been observed. As literatures suggest high frequency oscillation occurs in network of layer5pyramidal cells. Moreover, the level of cortical inhibition is low in group1and3which lack10-20Hz frequency oscillation. Therefore, our results may support the role cortical inhibition plays in synaptic plasticity.