Retinal implants incorporating a light-sensitive electrode array may circumvent this problem (Chow et al., 2004), as would an intraocular camera (Hauer, 2009), which may possibly be adapted for a cortical prosthesis. Importantly, such techniques may only be useful in those subjects not demonstrating significant gaze instability or suffering from nystagmus (Schneider et al., 2013). The work of Dobelle (2000) provided clear evidence that preserved neuroplasticity in visual cortex can permit a blind individual, who had an initially poor response to patterned stimulation, to gradually recognize

shapes, letters and features in a relatively complex physical environment. According to Dobelle (2000), a key factor in achieving this goal was increased computing power, which permitted the use of more sophisticated image processing algorithms providing enhanced edge detection, whilst keeping frame FK866 purchase rates at acceptable levels. Future cortical visual prostheses will likely elicit several hundred or more

phosphenes (Lowery, 2013, Normann et al., 2009 and Srivastava et al., 2007), many more than were reported by any previous cortical implant recipient (Brindley and Lewin, 1968, Brindley et al., 1972, Brindley, 1982, Dobelle, 2000 and Naumann, 2012). The manner http://www.selleckchem.com/products/Rapamycin.html in which visual imagery is preprocessed prior to reconstruction with phosphenes is therefore of great importance, and is a subject of ongoing research. Early studies of simulated phosphene vision used simple perforated masks of varying density and “pixel” count, which provide a crude estimate of the likely pattern of percepts experienced by

a cortical prosthesis recipient (Cha et al., 1992a). This technique provides PJ34 HCl a model for many subsequent reports of simulated phosphene imagery, namely that the phosphenated image is a grayscale, “downsampled” version of the original, with multiple levels of brightness allowable per pixel. Some more recent studies have added irregularities in the distribution and character of percepts including variable size, brightness, density, overlap and a restricted spread of phosphenes across the visual field to more accurately estimate the perceptual experience (Chen et al., 2009b and Srivastava et al., 2009). Nonetheless, the same approach is essentially employed, wherein the resultant image remains a downsampled version of the original, albeit with phosphenes conforming to a more realistic electrode/phosphene coordinate system. Chen et al. (2009b) discussed in detail the likely implications of phosphene maps with poor resolution and contrast, restricted fields of view, high eccentricity in the main phosphene field, geometric distortions in images and other such limitations for the rehabilitation of visual prosthesis recipients.