Scientific American: Psychology
From the Pages Activity

SEEING BLIND

A visually impaired woman can still perceive motion.

Milena Canning can see steam rising from a coffee cup but not the cup. She can see her daughter’s ponytail swing from side to side, but she can’t see her daughter. Canning is blind, yet moving objects somehow find a way into her perception. Scientists studying her condition say it could reveal secrets about how humans process vision in general.

Canning was 29 when a stroke destroyed her entire occipital lobe, the brain region housing the visual system. The event left her sightless, but one day she saw a flash of light from a metallic gift bag next to her. Her doctors told her she was hallucinating. Nevertheless, “I thought there must be something happening within my brain [allowing me to see],” she says. She went from doctor to doctor until she met Gordon Dutton, an ophthalmologist in Glasgow, Scotland. Dutton had encountered this mystery before—in a 1917 paper by neurologist George Riddoch describing brain-injured World War I soldiers. To help enhance Canning’s motion-based vision, Dutton prescribed her a rocking chair.

Canning is one of a handful of people who have been diagnosed with the “Riddoch phenomenon,” the ability to perceive motion while blind to other visual stimuli. Jody Culham, a neuroscientist at Western University in Ontario, and her colleagues launched a 10-year investigation into Canning’s remarkable vision and published the results online . . . in Neuropsychologia. The team confirmed that Canning was able to detect motion and its direction. She could see a hand moving toward her, but she could not tell a thumbs-up from a thumbs-down. She was also able to navigate around obstacles, reach and grasp, and catch a ball thrown at her.

Scans of Canning’s head showed an apple-sized hole where the visual cortex should be. But the lesion apparently spared the brain’s motion-processing region, the middle temporal (MT) visual area. “All the credit [for Canning’s perception] must go to an intact MT,” says Beatrice de Gelder, a neuroscientist at Maastricht University in the Netherlands, who was not involved in the study.

The next mystery is how information from the eyes gets to the MT without traveling through the visual cortex. “I think of the primary visual pathway as a highway. In Milena’s case, the highway dead-ends, but there are all these side roads that go to the MT,” Culham says. “It’s got to be one of these indirect routes, but we are not yet sure which one.” These side roads most likely exist in all our brains as remnants of the early visual system that evolved to detect approaching threats even without full-fledged sight, Culham says…

Bahar Gholipour. Reproduced with permission. Copyright © 2018 Scientific American, a division of Nature America, Inc. All rights reserved.

Quiz

1Canning was 29 when a stroke destroyed her entire occipital lobe, the brain region housing the blank system.
2Doctors confirmed that the stroke that caused Milena’s blindness had left an apple-sized hole in her visual cortex located in the blank lobe.
3Riddoch syndrome, the phenomenon that caused Milena’s specific case to be of interest to researchers and neurologists, was that she had the ability to see
4Which factor may have contributed to Milena Canning’s ability to "see blind”?
5Neurologist George Riddoch wrote a paper in 1917 describing his experience with the phenomenon of “seeing blind” while working with:
Activity Type Title

Chapter 1. Chapter 4

From the pages

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1.1 Quiz

1.

_max_tries:1 _feedback_correct: Correct. _feedback_incorrect: Incorrect.

Canning was 29 when a stroke destroyed her entire occipital lobe, the brain region housing the _________ system.

A.
B.
C.
D.

2.

_max_tries:1 _feedback_correct: Correct. _feedback_incorrect: Incorrect.

Doctors confirmed that the stroke that caused Milena’s blindness had left an apple-sized hole in her visual cortex located in the __________ lobe.

A.
B.
C.
D.

3.

_max_tries:1 _feedback_correct: Correct. _feedback_incorrect: Incorrect.

Riddoch syndrome, the phenomenon that caused Milena’s specific case to be of interest to researchers and neurologists, was that she had the ability to see

A.
B.
C.
D.

4.

_max_tries:1 _feedback_correct: Correct. _feedback_incorrect: Incorrect.

Which factor may have contributed to Milena Canning’s ability to "see blind”?

A.
B.
C.
D.

5.

_max_tries:1 _feedback_correct: Correct. _feedback_incorrect: Incorrect.

Neurologist George Riddoch wrote a paper in 1917 describing his experience with the phenomenon of “seeing blind” while working with:

A.
B.
C.
D.