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The Man Who Could (Not) See Faces In one famous case study, a man who was completely blind could distinguish among photographs of happy and angry faces at a rate better than chance. Scientists learned that visual information was reaching his amygdala, a region that processes potential threats. Activity in his amygdala increased in response to faces that were gazing directly at him. When asked, he could not guess which pictures contained direct or averted gazes—yet his amygdala appeared to register which was which. —V.S.

Why some people believe they can see their hands in total darkness Many people swear by the so-called spelunker’s illusion, in which they think they can see their own hands moving even in the total absence of light. You don’t have to see it to believe it: in a recent article in Psychological Science, cognitive scientists based at Vanderbilt University and the University of Rochester have dem-onstrated that this spooky illusion is real, and some individuals are more prone to these visions than others.

Through a series of � ve experiments, the researchers asked their 129 subjects to report visual sensation in total darkness. In the � rst four setups, subjects wore a blindfold to block all light. A subset of these participants claimed to see movement when they waved their own hand in front of their face but not when an experimenter waved his hand.

Why would only some people think they could see the motion? On the hunch that this illusion was created by intense connectivity among brain regions, the research team had included volunteers with a form of synesthesia, in which heightened brain connectivity causes letters and numbers to appear as certain colors. These subjects, they discovered, had even stronger visual reactions to their own hands moving in the darkness than did the other subjects.

Finally, the researchers decided to try out the experiment using eye-tracking headgear, again in complete darkness. The eye tracker revealed that the more vividly a subject reported seeing his or her own hand’s motion, the smoother the eye movements were. That is, their eyes behaved as though they really could “see” and were locking onto an imaginary target. In reality the participant was anticipating the visual experience of his or her hand in space.

Taken together, the studies suggest that people with heightened connectivity between the senses possess a greater awareness of the body. The � ndings are also a reminder that “sight” is generated by your brain, not your eyes. “The brain may or may not use information your eyes provide,” says Rochester cognitive scientist Duje Tadin. Instead your brain uses the eyes’ information selectively alongside familiar or predictable patterns—such as your hands’ movements—to construct what you ultimately perceive. — Daisy Yuhas

NO VISION NECESSARY TO “SEE” LIGHTLight triggers a quick neural reaction even in blind peopleThe presence of light may do more for us than merely allow for sight. A study by Gilles Vandewalle and his colleagues at the University of Montreal suggests that light affects important brain functions—even in the absence of vision.

Previous studies have found that certain photoreceptor cells located in the retina can detect light even in people who do not have the ability to see. Yet most studies suggested that at least 30 minutes of light exposure is needed to signi� cantly affect cognition via these nonvisual pathways. Vandewalle’s study, which involved three completely blind participants, found that just a few seconds of light altered brain activity, as long as the brain was engaged in active processing rather than at rest.

First the experimenters asked their blind subjects whether a blue light was on or off, and the subjects answered correctly at a rate signi� cantly higher than random chance—even though they con� rmed they had no conscious perception of the light. Using functional MRI, the researchers then determined that less than a minute of blue light exposure triggered changes in activity in regions of their brain associated with alertness and executive function. Finally, the scientists found that if the subjects received simultaneous auditory stimulation, a mere two seconds of blue light was enough to modify brain activity. The researchers think the noise engaged active sensory processing, which allowed the brain to respond to the light much more quickly than in previous studies when subjects rested while being exposed to light.

The results con� rm that the brain can detect light in the absence of working vision. They also suggest that light can quickly alter brain activity through pathways unrelated to sight. The researchers posit that this nonvisual light sensing may aid in regulating many aspects of human brain function, including sleep/wake cycles and threat detection.

— Ariel Van Brummelen

distinguish among photographs of happy and angry faces

that processes potential threats. Activity in his amygdala increased in response to faces that were gazing directly

V.S.

their own hands moving in the darkness than did the other subjects.Finally, the researchers decided to try out the experiment using eye-Finally, the researchers decided to try out the experiment using eye-

revealed that the more vividly a subject reported seeing his or her own hand’s motion, the smoother the eye movements were. That is, their eyes behaved as though they really could “see” and were locking onto an imaginary target. In reality the participant was anticipating the visual

Taken together, the studies suggest that people with heightened connectivity between the senses possess a greater awareness of the

your brain, not your eyes. “The brain may or may not use information

familiar or predictable patterns—such as your hands’ movements—— Daisy Yuhas

NO VISION NECESSARY TO “SEE” LIGHTLight triggers a quick neural reaction even in blind peopleThe presence of light may do more for us than merely allow for sight. A study by Gilles Vandewalle and his colleagues at the University of Montreal suggests that light affects important brain functions—even in the absence of vision.

Previous studies have found that certain photoreceptor cells located in the retina can detect light even in people who do not have the ability to see. Yet most studies suggested that at least 30 minutes of light exposure is needed to signi� cantly affect cognition via these nonvisual pathways. Vandewalle’s study, which involved three completely blind participants, found that just a few seconds of light altered brain activity, as long as the brain was engaged in active processing rather than at rest.

First the experimenters asked their blind subjects whether a blue light was on or off, and the subjects answered correctly at a rate signi� cantly higher than random chance—even though they con� rmed they had no conscious perception of the light. Using functional MRI, the researchers then determined that less than a minute of blue light exposure triggered changes in activity in regions of their brain associated with alertness and executive function. Finally, the scientists found that if the subjects received simultaneous auditory stimulation, a mere two seconds of blue light was enough to modify brain activity. The researchers think the noise engaged active sensory processing, which allowed the brain to respond to the light much more quickly than in previous studies when subjects rested while being exposed to light.

The results con� rm that the brain can detect light in the absence of working vision. They also suggest that light can quickly alter brain activity through pathways unrelated to sight. The researchers posit that this nonvisual light sensing may aid in regulating many aspects of human brain function, including sleep/wake cycles and threat detection.

— Ariel Van Brummelen— Ariel Van Brummelen—

SEE ING WITH THE BRAIN (NOT THE EYES)

The Spelunker’s Illusion

Dream visions may originate from random activity in the visual centers in the brain or in regions that store memories, which connect to visual areas.

To develop a child’s social reasoning skills, try to pepper your speech with “thought words” such as know, forget, think and understand. l Brain scans can predict a child’s future working memory, a capacity similar to a mental scratch pad, which in turn predicts academic success.

miq314News3p.indd 19 3/7/14 5:03 PM