P2 component latency of fVEP as a bioindicator for clinical and diagnostic use in visual pathologies

Purpose

The signaling of flash visual evoked potential (fVEP) derives from the retina, but how retinal activity influences fVEP remains unclear. This work aimed to decipher the specific retinal kinetic contributions to fVEP response.

Methods

Monocular and simultaneous recordings of flash VEP and electroretinogram were performed. Healthy and adult mice C57BL/6J were used. The right eye was injected intravitreally with 1 μL of PBS containing 25 mM APB, 10 mM Bicuculline, 30 mM DNQX, 100 mM Glutamate, 100 mM GABA, 5 mM TPMPA, or 25 mM HEPES. The left eye was injected with 1 μL of PBS and then wore an opaque patch. The amplitude and latency of fVEP were analyzed in detail.

Results

In the control group, at light intensity ≤ 0.1 cd·s/m², four robust components of the fVEP recordings, N1, P1, N2, and P2, were identified in dark adaptation conditions. After administration reagents, N1 and P1 components were abolished by APB, Bicuculline, DNQX or TPMPA, but were preserved by GABA/Glutamate or HEPES. Notably, N2 and P2 components were always kept. The latency and amplitude of fVEP were shown to be stimulus-dependent. Nevertheless, the amplitude showed greater inter-individual variability than latency.

Conclusion

N1 and P1 components are strongly related to rod photoreceptor activity and/or the level of horizontal cell excitation. Latency, rather than fVEP amplitude, could be a good biomarker for clinical and diagnostic purposes, particularly the P2 latency in the rod-driven scotopic response.