Skip to Content

Department of Cognitive Science

Seeing Clearly: Examining The Consequences Of Glaucoma For The Human Brain

Glaucoma is a progressive optic neuropathy characterized by a specific pattern of optic disc damage and ganglion cell loss. If untreated it leads to blindness, and it remains one of the 3 major causes of blind registrations in Australia. Despite considerable deficits on objective testing, glaucoma patients are often unaware of their scotoma (blind spot). In the early stages of the disease, the cortex somehow ‘fills in’ the gaps, so patients do not see black regions associated with their loss of vision. There is the possibility that adjacent striate or higher cortical areas recruit unused neurons corresponding to the scotoma as a form of neural plasticity. The broad aim of this project is to investigate the way the brain adapts to changes in visual input due to a scotoma.

The ability of the brain to ‘fill in’ missing visual information has been well documented using ‘artificial scotomas’, the physiological blind spot. This study will compare brain adaptations resulting from scotomas to those of the physiological blind spot (artifical scotoma) using both functional MRI to examine plasticity in the brain after retinal damage and behavioural studies examining the behavioural consequences of such plasticity. The findings of this research will help us understand the glaucoma process and how to possibly detect visual loss at an earlier stage of the disease.

Responses of deprived V1 to stimulation near region of scotomaPreliminary findings

We used functional magnetic resonance imaging (fMRI) to examine the response of deprived primary visual cortex (V1) to stimulation around the region of the scotoma in patients with monocular glaucoma (Figure 1). As one would expect, stimulating within the scotoma resulted in less activity in V1 in the affected versus the ‘good’ eye. In contrast, stimulating the area adjacent to the scotoma resulted in hyperactivity of deprived V1, a much greater response than identical stimulation in the good eye (Figure 2). Visual cortex with abnormal input seems to ‘extrapolate’ from adjacent areas, which prevents awareness of the scotoma in glaucoma. This extrapolation may reflect the filling-in processes that support conscious vision in general.

fMRI results from seven glaucoma patients

Publications

  1. Graham, S.L., Rich, A.N., Klistorner, A., & Williams, M.A. (In Press). Functional MRI reveals activation of visual cortex by adjacent stimuli in glaucomatous scotoma regions - perceptual fill-in? [Abstract]. Investigative Ophthalmology and Visual Science.
  2. Williams, M.A., Rich, A.N., Klistorner, A., & Graham, S. (In Press). Neural filling-in? Increased response in deprived visual cortex when regions adjacent to a glucomatous scotoma are stimulated [Abstract]. Perception.
  3. Smith, F., Rich, A., Graham, S., de Lissa, P., Brooks, K., & Williams, M.A. (In Press). ‘Filling-in’ of stimuli at the physiological blind spot reflects lateral connection rather than feedback [Abstract]. Clinical EEG and Neuroscience

Further Information

Seminars

Who is Visiting

Contact Details

Telephone: (02) 9850 9599
Fax : (02) 9850 6059
Email : cogsci@mq.edu.au
Web : www.cogsci.mq.edu.au