Rajkumar Raveendran - Academia.edu (original) (raw)
Uploads
Papers by Rajkumar Raveendran
I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, inc... more I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public.
Investigative Ophthalmology & Visual Science, 2013
Collinear flanking stimuli can reduce the detectability of a Gabor target presented in peripheral... more Collinear flanking stimuli can reduce the detectability of a Gabor target presented in peripheral vision. This phenomenon is called collinear lateral inhibition and it may contribute to crowding in peripheral vision. Perceptual learning can reduce collinear lateral inhibition in peripheral vision, however intensive training is required. Our aim was to assess whether modulation of collinear lateral inhibition can be achieved within a short time-frame using a single 20-minute session of primary visual cortex anodal transcranial direct current stimulation (a-tDCS). Thirteen observers with normal vision performed a 2AFC contrast detection task with collinear flankers positioned at a distance of 2λ from the target (lateral inhibition) or 6λ (control condition). The stimuli were presented 6° to the left of a central cross and fixation was monitored with an infra-red eye tracker. Participants each completed two randomly sequenced, single-masked stimulation sessions; real anodal tDCS and sh...
Investigative Ophthalmology & Visual Science, 2019
Investigative Ophthalmology & Visual Science, 2016
People with central vision loss (CVL) due to macular degeneration are forced to rely on their res... more People with central vision loss (CVL) due to macular degeneration are forced to rely on their residual peripheral vision and often develop a preferred retinal locus (PRL), a region of intact peripheral retina that is used for fixation. At the PRL, visual processing is impaired due to crowding (cluttering of visual objects). The problem of crowding still persists when images are magnified to account for the lower resolution of peripheral vision. We assessed whether anodal transcranial direct stimulation (a-tDCS), a neuro-modulation technique that alters cortical inhibition, would reduce collinear inhibition (an early component of crowding) when applied to the visual cortex in patients with CVL. Our results showed that applying a-tDCS to the visual cortex for 20mins reduced crowding in three patients with CVL and that the effect was sustained for up to 30mins. Sham stimulation delivered in a separate session had no effect. These initial observations mandate further research into the u...
I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, inc... more I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public.
Investigative Ophthalmology & Visual Science, 2013
Collinear flanking stimuli can reduce the detectability of a Gabor target presented in peripheral... more Collinear flanking stimuli can reduce the detectability of a Gabor target presented in peripheral vision. This phenomenon is called collinear lateral inhibition and it may contribute to crowding in peripheral vision. Perceptual learning can reduce collinear lateral inhibition in peripheral vision, however intensive training is required. Our aim was to assess whether modulation of collinear lateral inhibition can be achieved within a short time-frame using a single 20-minute session of primary visual cortex anodal transcranial direct current stimulation (a-tDCS). Thirteen observers with normal vision performed a 2AFC contrast detection task with collinear flankers positioned at a distance of 2λ from the target (lateral inhibition) or 6λ (control condition). The stimuli were presented 6° to the left of a central cross and fixation was monitored with an infra-red eye tracker. Participants each completed two randomly sequenced, single-masked stimulation sessions; real anodal tDCS and sh...
Investigative Ophthalmology & Visual Science, 2019
Investigative Ophthalmology & Visual Science, 2016
People with central vision loss (CVL) due to macular degeneration are forced to rely on their res... more People with central vision loss (CVL) due to macular degeneration are forced to rely on their residual peripheral vision and often develop a preferred retinal locus (PRL), a region of intact peripheral retina that is used for fixation. At the PRL, visual processing is impaired due to crowding (cluttering of visual objects). The problem of crowding still persists when images are magnified to account for the lower resolution of peripheral vision. We assessed whether anodal transcranial direct stimulation (a-tDCS), a neuro-modulation technique that alters cortical inhibition, would reduce collinear inhibition (an early component of crowding) when applied to the visual cortex in patients with CVL. Our results showed that applying a-tDCS to the visual cortex for 20mins reduced crowding in three patients with CVL and that the effect was sustained for up to 30mins. Sham stimulation delivered in a separate session had no effect. These initial observations mandate further research into the u...