Recording of visual-evoked potentials in dogs with scalp electrodes

Area of Science:

• Neuroscience
• Ophthalmology
• Veterinary Medicine

Background:

• Recording visual-evoked potentials (VEPs) in dogs using scalp electrodes has been challenging.
• High-amplitude electroretinograms (ERGs) from white light stimulation can obscure VEP signals.
• A novel stimulation technique is needed to improve VEP recording accuracy in canines.

Purpose of the Study:

• To develop and validate a new stimulation technique for reliable VEP recording in dogs.
• To differentiate VEPs from ERGs in canine subjects.
• To characterize the VEP components in anesthetized dogs.

Main Methods:

• Utilized red light stimulation after light adaptation to selectively stimulate cones and reduce ERG amplitude.
• Performed simultaneous ERG and VEP recordings in dogs under different anesthesia protocols (chloralose, halothane, thiopental).
• Analyzed VEPs for the presence and latency of negative peaks (N1, N2, N3).

Main Results:

• Red light stimulation significantly reduced ERG amplitude, allowing for clearer VEP identification.
• VEPs were characterized by three distinct negative peaks: N1, N2, and N3.
• N1 was the most consistently recorded peak (85%), followed by N3 (38%) and N2 (31%).
• Anesthesia was essential to eliminate artifacts in conscious or sedated dogs.
• No significant effect of thiopental and/or halothane on measured latencies compared to chloralose was observed.

Conclusions:

• The red light stimulation technique is effective for recording VEPs in dogs.
• Anesthesia is critical for artifact-free VEP recordings in canine studies.
• The characterized VEP peaks (N1, N3) provide valuable data for assessing canine visual function.