Note: [] Correspondence to: C. Mark Wessinger, Center for Cognitive
Neuro-science and Department of Psychology, HB 6162 Silsby Hall, Dartmouth
College, Hanover, NH 03755, USA; Tel.: 603-646-0279; Fax: 603-646- 1181;
E-mail: [email protected]
Abstract: Using stabilized visual field mapping techniques, seven hemianopic
subjects were extensively investigated for residual visual abilities. Iso-lated
islands of detection abilities were demonstrated by four of these subjects.
Additional abilities demonstrated within these islands included saccadic and
verbal localization, wavelength discrimination, form discrimination, and motion
detection. These abilities were also accompanied by low-confidence ratings, and
thus have the character of blindsight. It is noteworthy that different subjects
demonstrated different abilities at different visual field locations,
underscoring the between and within subject variability often observed with
blindsight. Furthermore, magnetic resonance images obtained for each subject
demonstrated variable sparing of occipital cortex. Such cortical sparing, in
conjunction with the behavioral variability, supports the notion that some
instances of blindsight are mediated by remnants of the primary visual
pathway.
Keywords: Blindsight, hemianopia, stabilized visual field mapping, residual vision, islands of vision
