Spatiotemporal properties of multipeaked electrically evoked potentials elicited by penetrative optic nerve stimulation in rabbits.
OBJECTIVE
To investigate the spatiotemporal properties of the cortical responses elicited by intraorbital optic nerve (ON) stimulation with penetrating electrodes as means of designing optimal stimulation strategies for an ON visual prosthesis.


METHODS
The ON of rabbits was exposed by orbital surgery for electrical stimulation. Craniotomy was performed to expose the visual cortex contralateral to the operated eye. Electrically evoked potentials (EEPs) were recorded by an electrode array positioned on the visual cortex.


RESULTS
There were primarily four components (N1, P1, P2, P3) in EEPs with implicit times of 8.0 ± 0.6, 11.3 ± 1.3, 20.5 ± 1.4, and 26.9 ± 1.5 ms, respectively, when the ON was stimulated by penetrating electrodes. The thresholds to elicit these components were different, and the higher thresholds were seen with slower cortical components. The corresponding thresholds were 13.8 ± 3.1 μA for N1, 21.8 ± 4.7 μA for P1, 36.4 ± 11.4 μA for P2, and 68.4 ± 17.2 μA for P3. The time courses of the EEP components were also distinct. The locations of EEPs with the maximum P1 amplitude showed a spatial correspondence to the ON stimulation sites. Different profiles of cortical responses could be discriminated when the ON stimulation sites were separated by 150 μm.


CONCLUSIONS
Multiple components with different properties were elicited in EEPs when the ON was stimulated by penetrating electrodes. Retinotopic and localized stimulation could be achieved with this stimulating approach.
Sun
Jingjing
J
Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
Lu
Yiliang
Y
Cao
Pengjia
P
Li
Xiaoliang
X
Cai
Changsi
C
Chai
Xinyu
X
Ren
Qiushi
Q
Li
Liming
L
D000818:Animals; D003399:Craniotomy; D004558:Electric Stimulation / Q000379:methods*; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual / Q000502:physiology*; D009900:Optic Nerve / Q000502:physiology*; D009915:Orbit; D010775:Photic Stimulation; D011817:Rabbits; D014793:Visual Cortex / Q000502:physiology*