The coupling of vision with locomotion in cortical blindness.
Maintaining or modifying the speed and direction of locomotion requires the coupling of the locomotion with the retinal optic flow that it generates. It is shown that this essential behavioral capability, which requires on-line neural control, is preserved in the cortically blind hemifield of a hemianope. In experiments, optic flow stimuli were presented to either the normal or blind hemifield while the patient was walking on a treadmill. Little difference was found between the hemifields with respect to the coupling (i.e. co-dependency) of optic flow detection with locomotion. Even in the cortically blind hemifield, faster walking resulted in the perceptual slowing of detected optic flow, and self-selected locomotion speeds demonstrated behavioral discrimination between different optic flow speeds. The results indicate that the processing of optic flow, and thereby on-line visuo-locomotor coupling, can take place along neural pathways that function without processing in Area V1, and thus in the absence of conscious intervention. These and earlier findings suggest that optic flow and object motion are processed in parallel along with correlated non-visual locomotion signals. Extrastriate interactions may be responsible for discounting the optical effects of locomotion on the perceived direction of object motion, and maintaining visually guided self-motion.
Department of Electronics, University of York, York Y010 5DD, UK. Electronic address: adar.pelah@york.ac.uk.
Adar
A
Pelah
School of Health Sciences, City University London, London EG1V 0HB, UK.
John
J
Barbur
Girton College, University of Cambridge, Cambridge CB3 0JG, UK.
Adrian
A
Thurrell
Department of Psychology, The Center for Complex Systems and Brain Science, Florida Atlantic University, Boca Raton, FL 33486, USA.
Howard S
HS
Hock
D000328:Adult; D019575:Blindness, Cortical / Q000503:physiopathology*; D006423:Hemianopsia / Q000503:physiopathology; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D057849:Optic Flow / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology; D016138:Walking
Blindsight; Cortical blindness; Hemianopia; Locomotion; Optic flow; Treadmill