[The spatiotemporal frequency tuning of pattern visual evoked potentials in rats].

Objective: To observe the spatiotemporal frequency tuning of pattern visual evoked potentials in Wistar rats.

Methods: Experimental study. 15 Wistar rats of 8 weeks old were used in this study. Recording electrodes were chronically inserted into the skull without piercing the dura at the corresponding sites to the primary visual cortex under anesthesia. Reference electrodes were inserted into the nose bone in the same way. Pattern visual evoked potentials were recorded on the 3(rd), 5(th), 7(th) and 9(th) postoperation days. The visual stimuli were chessboard patterns with spatial frequency of 0.01, 0.02, 0.04 or 0.08 cpd, and temporal frequency of 1, 2, 4 or 6 Hz, respectively. Data were processed and statistically analyzed with Matlab and SPSS. The amplitudes and latencies of pattern visual evoked potentials under different spatial and temporal frequencies, the inter-individual variations and the repeated measurement variations were compared.

Results: With the increase of spatial frequencies, the P100 amplitudes of PVEPs were gradually reduced, which were (29.87 ± 10.37) µV (0.01 cpd), (31.92 ± 10.98) µV (0.02 cpd), (28.46 ± 6.18) µV (0.04 cpd) and (20.71 ± 6.54) µV(0.08 cpd), respectively, with significant difference among groups (F = 3.725, P = 0.018), and the P100 latencies of PVEPs were gradually elongated, which were (96.25 ± 12.12) ms (0.01 cpd), (95.73 ± 15.13) ms (0.02 cpd), (101.75 ± 8.11) ms (0.04 cpd) and (125.58 ± 18.32) ms (0.08 cpd), respectively, with significant difference among groups (F = 12.187, P = 0.000) . With the increase of temporal frequencies, the P100 amplitudes of PVEPs were gradually reduced, which were (30.71 ± 8.25) µV (1 Hz), (29.75 ± 4.76) µV (2 Hz), (25.79 ± 8.51) µV (4 Hz) and (19.63 ± 6.00) µV (6 Hz), with significant difference among groups (F = 6.115, P = 0.001), and there was no change of P100 latencies, which were (102.58 ± 16.09) ms (1 Hz), (101.75 ± 10.32) ms (2 Hz), (104.25 ± 12.51) ms (4 Hz) and (102.67 ± 13.59) ms (6 Hz), respectively, with no significant difference among groups (F = 0.074, P = 0.974). The inter-individual variation was the smallest under the spatial frequency of 0.04 cpd and temporal frequency of 2 Hz. The repeated measurement variations showed no significant change under tested conditions.

Conclusion: Under appropriate stimuli and recording conditions, PVEP can be reliably recorded in Wistar rats. The spatiotemporal frequency tuning of P100 amplitudes of Wistar rats exhibit low-pass selectivity. The spatial frequency affects the P100 latency in Wistar rat, but not so does the temporal frequency.