AVRC: Clinical and Physiological Optics research group

Blindsight and residual vision studies in patients with damaged central visual pathways

Summary:

We know that damage to the geniculostriate projection or to the striate cortex in human subjects results in what are defined clinically as blind areas in the corresponding parts of the retinal-cortical map. Evidence that has emerged from a number of studies shows that subjects can often perform well above change when forced to make judgements based on visual information that is restricted to the clinically blind areas of the visual field. Under some stimulus conditions, particularly those involving high contrast, fast moving stimuli, the subjects also experience some conscious awareness of something happening in the visual field. This form of residual vision has been investigated in a number of studies and shown to depend of the spatiotemporal and chromatic properties of the stimulus. We are currently interested in establishing the level of residual processing of motion information in the absence of a direct geniculostriate input and the extent to which residual processing of motion and chromatic informa

Collaborators in this work are Alan Cowey (University of Oxford), Arash Sahraie (University of Aberdeen), Steve Williams and Andrew Simmons (Institute of Psychiatry, London UK).

References:

Barbur JL, Weiskrantz L, Harlow JA. (1999). The unseen color aftereffect of an unseen stimulus: insight from blindsight into mechanisms of color afterimages. Proc. Natl. Acad. Sci. (U.S.A.), 96: 11637-11641.

Pelah A, Barbur JL. Walking (1999). Speed rating and direction discrimination from optic flow in the absence of V1. Investigative Ophthalmology & Visual Science, 40: S765.

Weiskrantz L, Cowey A, Barbur JL (1999). Differential pupillary constriction and awareness in the absence of striate cortex. Brain, 122: 1533-1538.

Barbur JL, Sahraie A, Simmons A, Weiskrantz L, Williams SC (1998). Residual processing of chromatic signals in the absence of a geniculostriate projection. Vision Res, 38: 3347-3353.

Pelah A, Barbur JL. (1998) Adaptation to visual motion and self-motion in the absence of V1. Perception, 27: 22-22.

Sahraie A, Weiskrantz L, Barbur JL. (1998). Awareness and confidence ratings in motion perception without geniculo-striate projection. Behav. Brain Res., 96: 71-77.

Barbur JL, Cole VA, Sahraie A, Simmons A, Weiskrantz L, Williams SCR. (1997). A study of pupil responses in a subject with damaged primary visual cortex. Investigative Ophthalmology & Visual Science, 38: 71-71.

Sahraie A, Weiskrantz L, Barbur JL, Simmons A, Williams SCR (1997). Motion processing with and without awareness: pattern of increased brain activity using fMRI. Investigative Ophthalmology & Visual Science, 37: p223.

Sahraie A, Weiskrantz L, Barbur JL, Simmons A, Williams SC, Brammer MJ. (1997). Pattern of neuronal activity associated with conscious and unconscious processing of visual signals. Proc. Natl. Acad. Sci., USA., 94: 9406-9411.

Weiskrantz L, Barbur JL, Sahraie A. (1995). Parameters affecting conscious versus unconscious visual discrimination with damage to the visual cortex (V1). Proc. Natl. Acad. Sci. U.S.A., 92: 6122-6126.

Barbur, J. L., Harlow, A. J., Sahraie, A., Stoerig, P., and Weiskrantz, L. (1994). Responses to chromatic stimuli in the absence of VI: pupillometric and psychophysical studies. In Vision Science and its Application (Technical Digest Series). Vol. 2, 312-315. Optical Society of America. Washington DC.

Barbur JL, Harlow AJ, Weiskrantz L. (1994). Spatial and temporal response properties of residual vision in a case of hemianopia. Phil. Trans. R. Soc. Lond. B, 343: 157-166.

Supported by:

John Barbur Applied Vision Research Centre | Clinical and Physiological Optics

This page was last updated on 12th March 2001.