Survival of retinal ganglion cells after damage to the occipital lobe in humans is activity dependent

Abstract

Damage to the optic radiations or primary visual cortex leads to blindness in all or part of the contralesional visual field. Such damage disconnects the retina from its downstream targets and, over time, leads to trans-synaptic retrograde degeneration of retinal ganglion cells. To date, visual ability is the only predictor of retinal ganglion cell degeneration that has been investigated after geniculostriate damage. Given prior findings that some patients have preserved visual cortex activity for stimuli presented in their blind field, we tested whether that activity explains variability in retinal ganglion cell degeneration over and above visual ability. We prospectively studied 15 patients (four females, mean age = 63.7 years) with homonymous visual field defects secondary to stroke, 10 of whom were tested within the first two months after stroke. Each patient completed automated Humphrey visual field testing, retinotopic mapping with functional magnetic resonance imaging, and spectral-domain optical coherence tomography of the macula. There was a positive relation between ganglion cell complex (GCC) thickness in the blind field and early visual cortex activity for stimuli presented in the blind field. Furthermore, residual visual cortex activity for stimuli presented in the blind field soon after the stroke predicted the degree of retinal GCC thinning six months later. These findings indicate that retinal ganglion cell survival after ischaemic damage to the geniculostriate pathway is activity dependent.

Visual Field Reconstruction in Hemianopia Using fMRI Based Mapping Techniques

“…Two blindsight positive patients (P6, P8) showed retained fMRI signal in the blindsight test zone using both MP and pRF techniques, albeit not completely normal. This is consistent with previous studies ( Papanikolaou et al, 2014 ; Schneider et al, 2019 ; Sanchez-Lopez et al, 2020 ), and suggests that both methods can reveal preserved visual processing in hemianopia beyond SAP. Interestingly, the blindsight stimulus in both patients overlapped the border of preserved and absent signal, raising the possibility that fMRI sensitivity may simply reflect better resolution than perimetry at the border zones of field loss.…”

“…The study of Barbot et al (2020) also found that the strength of V1 activity in perimetrically blind regions predicted the amount of improvement following training, although there was little change in activity after training. In a similar vein, Schneider et al (2019) found that hemianopic patients showing fMRI activity in the visual cortex soon after their stroke showed less ganglion cell loss 6 months later. Understanding how this neural activity across the visual cortex relates to residual function may provide the basis for designing personalized rehabilitation programs that target spared visual pathways in patients.…”

“…However, this type of test, while critical for practical issues such as suitability for driving, does not reveal any non-conscious vision that is often present in patients with hemianopia ( Stoerig and Cowey, 1989 , 1992 , 1997 ; Weiskrantz, 1993 , 1996 ; Tomaiuolo et al, 1997 ; Tamietto and de Gelder, 2008 ; Ajina et al, 2015 ; Ajina and Bridge, 2018 , 2019 ; Danckert et al, 2019 ; Sanchez-Lopez et al, 2020 ). The definition of regions of the VF as “blind” based on perimetric measures additionally does not reflect the finding that stimulation within this blind field can lead to neural activity in the visual areas of the brain ( Barbur et al, 1993 ; Morland et al, 2001 ; Bridge et al, 2008 ; Radoeva et al, 2008 ; Tinelli et al, 2013 ; Papanikolaou et al, 2014 ; Schneider et al, 2019 ; Sanchez-Lopez et al, 2020 ). Disadvantages of SAP therefore consist of its low spatial specificity, the high performance and attention required by the participant, the fact that it only captures conscious vision and its limited flexibility in testing stimuli.…”

Empty Sella Syndrome as a Window Into the Neuroprotective Effects of Prolactin

“…Recovery after retinal thinning, as measured by OCT varies with pathology ( 41 – 43 , 45 , 55 , 59 , 60 ). Optic neuritis patients experience recovery of visual function with increasing VEP amplitudes despite continued loss of pRNFL thickness and significant optic nerve atrophy over 12 months ( 61 ).…”

“…Macular central subfield (CST), ganglion cell layer (GCL), inner plexiform layer (IPL) and pRNFL thickness measurements were processed independently by Carl Zeiss Meditec, Inc. Ganglion cell complex (GCC) thickness was calculated using the sum of GCL and IPL layers. Measures of retinal thickness were subsequently mapped onto visual space using an in-house pipeline implemented in MATLAB ( 45 ) and analyzed with respect to visual hemi-field (i.e., the averaged thickness of homonymous hemiretinas) for comparison with optic tract integrity. To account for contributions from nasal vs. temporal halves, retinal measures were weighted 53% contribution from nasal hemi-retina and 47% for temporal hemi-retina ( 46 ).…”