Preservation of retinotopic map in retinal degeneration.
Retinal degenerations trigger the loss of photoreceptors and cause the remaining de-afferented neural retina to undergo remodeling. Concerns over this potential retinal synaptic reorganization following visual loss have raised questions regarding the usefulness of visual restoration via retinal electrical stimulation. We have used quantitative positron emission tomography (PET) and 2-deoxy-2-[18F]fluoro-d-glucose (FDG) to objectively evaluate the connection between the retina and the primary visual cortex under both light and transcorneal electrical stimulation (TcES) in five subjects with retinal degeneration (RD) who have had more than ten years of light-perception-only best visual acuity and five age-matched normal-sighted controls. All subjects underwent quantitative PET with FDG as the metabolic tracer during stimulation of the right eye under both light stimulation condition and transcorneal electrical stimulation (TcES) using ERG-Jet contact lens electrode. Cortical activation maps from each stimulation condition were obtained using statistical parametric mapping. TcES phosphene threshold current and qualitative visual cortex activation from both stimulation conditions were compared between the two subject groups. Average phosphene threshold current was 0.72 ± 0.18 mA for the five normal-sighted controls and 3.08 ± 2.01 mA for the retinal degenerative subjects. Phosphene threshold current was significantly higher in retinal degenerative subjects compared to normal-sighted controls (p < 0.05). We found both light stimulation and TcES resulted in retinotopically mapped primary visual cortex activation in both groups. In addition, the patterns of early visual area activation between the two subject groups are more similar during TcES than light stimulation. Our findings suggest primary visual cortex continues to maintain its retinotopy in RD subjects despite prolonged visual loss.
Doheny Eye Institute, University of Southern California, 1355 San Pablo St., DVRC-100, Los Angeles, CA 90033, USA. john.jianxie@gmail.com
John
J
Xie
Gene-Jack
GJ
Wang
Lindy
L
Yow
Mark S
MS
Humayun
James D
JD
Weiland
Carlos J
CJ
Cela
Hossein
H
Jadvar
Gianluca
G
Lazzi
Elona
E
Dhrami-Gavazi
Stephen H
SH
Tsang
D000328:Adult; D001931:Brain Mapping; D003623:Dark Adaptation; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000503:physiopathology; D010719:Phosphenes; D010775:Photic Stimulation; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012160:Retina / Q000503:physiopathology; D012162:Retinal Degeneration / Q000503:physiopathology*; D041623:Tomography, Optical Coherence; D014793:Visual Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014795:Visual Pathways / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18