Comparison of Electrical Stimulation Thresholds in Normal and Retinal Degenerated Mouse Retina

Abstract

The amount of electrical charge required to elicit an action potential is dependent on the condition of the retina and the shape of the stimulus pulse used to deliver the charge.

High-Resolution Electrical Stimulation of Primate Retina for Epiretinal Implant Design

“…Such stimulation attempts use much larger electrodes (125-500 m) and/or long-duration stimulation pulses (ϳ1 ms), and result in multiple evoked spikes at long latencies (ϳ10 ms). With these stimulation configurations, spike thresholds are typically much higher than the direct-activation values reported in this study (Jensen et al, 2003;Suzuki et al, 2004;Guven et al, 2005;Jensen and Rizzo, 2007;Ye and Goo, 2007). Results from the present study are most comparable with recently published reports of epiretinal stimulation that activated ganglion cells directly by using small electrodes and short pulses: 0.05-0.31 mC/cm 2 for 40 m disk electrodes in frog retina (Kuras et al, 2004), 0.14 -0.25 mC/cm 2 for 30 m cone-shaped electrodes in rabbit retina (Fried et al, 2006), and 0.02-0.20 mC/ cm 2 for 8 -12 m disk electrodes in rat retina (Sekirnjak et al, 2007).…”

“…Several groups have reported that degenerated retinas show higher thresholds than intact retinas, as measured mostly with large (100 -400 m) stimulation electrodes (Humayun et al, 1994;Katona et al, 1998;Rizzo et al, 2003;Suzuki et al, 2004). The long latencies in these studies indicate that they stimulated ganglion cells indirectly through the retinal neural network; currently no data for direct ganglion cell activation is available.…”

The Dependence of Spectral Impedance on Disc Microelectrode Radius

“…Therefore, a sin wave stimulus delivering the same amount of total charge as a square wave stimulus would likely excite a greater population of cells in the electrode center since it does not consist of the higher order harmonics present in the latter. It is interesting to note that early cortical stimulation studies used sin wave stimuli [24], [25], and it has been shown in isolated retina stimulation that sin wave pulses have a lower threshold for stimulation compared with square wave pulses of the same amplitude [26]. …”

Electronic restoration of vision in those with photoreceptor degenerations

“…Studies in humans and animals have found that the degenerated retina requires more current or higher thresholds to generate a neural response. 59,68,82,83 This may be due to the documented changes in the diseased retina, such as changes in cellular intrinsic properties, synaptic activity, glial scarring or a combination of all of these factors. 39,42,59,[83][84][85] The position of the electrodes relative to their target cells is another aspect that could affect device performance.…”