Reliability of VEP Recordings Using Chronically Implanted Screw Electrodes in Mice

Area of Science:

• Neuroscience
• Ophthalmology
• Biomedical Engineering

Background:

• Visual evoked potentials (VEPs) objectively assess visual function in animal models.
• Chronic electrode implantation is common for longitudinal rodent studies.
• Reliability of VEP recordings over extended periods requires assessment.

Purpose of the Study:

• To compare VEP reliability 1 and 7 days post-implantation in adult mice.
• To assess stimulus-independent changes in electroencephalogram (EEG) power and entropy over time.
• To evaluate the impact of electrode implantation on VEP recording stability.

Main Methods:

• Adult mice (n=7) underwent chronic implantation of stainless steel electrodes.
• VEPs and EEG activity were recorded 1 and 7 days post-implantation.
• Brain sections were analyzed for glial activation (GFAP) and cell death (TUNEL).

Main Results:

• VEP recordings showed high intra-session reliability.
• Inter-session reliability was poorer, with decreased VEP amplitudes and EEG power over time.
• Glial activation was observed, but no significant cell death occurred.
• Amplitude decrease was normalized by scaling to EEG power.

Conclusions:

• VEP responses are reliably recorded shortly after implantation but amplitude decreases over time.
• Time-dependent changes in cortical excitability impact longitudinal VEP studies.
• Future preclinical studies must consider temporal effects in VEP analysis.