VEP

Celeris VEP

Visually evoked potentials (VEPs) record signals from the visual cortex using a sub-dermal needle electrode. Visual potentials can be evoked with both a flash or pattern stimuli, and may be done in conjunction with ERG. 

VEP protocols

For the latest version of protocols, please contact Diagnosys Support. 

Flash ERG and VEP: Simultaneous recording of ERG and VEP in response to a flash stimulus  

Pattern ERG and VEP: Simultaneous recording of ERG and VEP in response to a pattern stimulus  

Pattern VEP: VEP response to a pattern stimulus 

Visual Pathway: A four step protocol that records from the retina (ERG & OPs), ganglion cells (PhNR), RPE (C-wave), and visual cortex (VEP). 

General tips

For optimal results, consider anesthesia, eye preparation, and animal positioning. Review instructions for positioning the full-field flash and pattern stimulators. 

VEP electrode placement 

To place the VEP needle electrode, begin by lifting the skin between the ears of the animal and inserting the needle subcutaneously from the ears towards the nose. Slide the needle horizontally along the skull, ensuring it is fully under the skin. The needle should be centered at the midline; tape may be used to hold the electrode in place. Note that consistent placement among your animal population helps ensure repeatability. 

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Electrode setup

Three electrodes are necessary:

(VEP) Active needle electrode at the visual cortex, as described above

(Ref) Reference needle electrode into the snout or cheek of the animal

(GND) Ground needle electrode into the hindquarters near the tail

Combination ERG and VEP tests require two stimulator-electrodes and three needle electrodes.

• Right Eye, Channel 1+
• Left Eye, Channel 1- 
• VEP needle, Channel 2+
• Reference needle, Channel 2- 
• Ground needle, GND

VEP-only tests still require stimulators, but the ERG electrodes can be omitted. The setup will be as follows: 

• VEP, Channel 1+
• Reference, Channel 1-
• Ground, GND

 

FAQ

Is there an alternative to the needle VEP electrode? 

Yes. Needle electrodes are convenient and relatively non-invasive, but placement may be variable to one test to another. Alternatively, screw electrodes can be implanted above the visual cortex to improve reproducibility and yield larger amplitudes. However, Diagnosys does not provide instruction on the use of this method. 

 

References

Hubener M. Mouse visual cortex. Current Opinion in Neurobiology. (2003) 13: 413-420. 

Ridder WH, Nusinowitz S. The visual evoked potential in the mouse – Origins and response characteristics. Vision Research (2006) 46: 902-913.

You Y, Klistorner A, Thie J, Graham SL. Improving reproducibility of VEP recordings in rats: electrodes, stimulus source and peak analysis. Documenta Ophthalmologica. (2011) 132: 109-119.