Tag: visual cortex

Blind man navigates obstacle course perfectly with no visual awareness

By Ed Yong | December 22, 2008 12:00 pm

The video above seems completely unremarkable at first – man walks down a corridor, navigating his way around easily visible and conspicuous obstacles. But it’s far from an easy task; in fact, it should be nigh-impossible. The man, known only as TN, is totally blind.

His inability to see stems from a failure in his brain rather than his eyes. Those work normally, but his visual cortex – the part of the brain that processes visual information – is inactive. As a result, TN is completely unaware of the ability to see and in his everyday life, he behaves like a blind person, using a stick to find his way around. Nevertheless, he can clearly make his way through a gauntlet of obstacles without making a single mistake.

TN was a doctor before two successive strokes destroyed his ability to see. The first one severely damaged the occipital lobe on the left side of his brain, which contains the visual cortex. About a month later, a second stroke took out the equivalent area on the right hemisphere. TN is one-of-a-kind, the only known patient with damage like this in the entire medical literature. The fibres that connect the occipital lobes on the right and left halves of the brain have also been severely damaged and tests reveal that no blood flows between these disconnected areas.

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CATEGORIZED UNDER: Medicine & health, Perception

The machine that identifies images from brain activity alone

By Ed Yong | March 5, 2008 1:01 pm

Blogging on Peer-Reviewed ResearchModern brain-scanning technology allows us to measure a person’s brain activity on the fly and visualise the various parts of their brain as they switch on and off. But imagine being able to literally see what someone else is thinking – to be able to convert measurements of brain activity into actual images.
Tank.jpgIt’s a scene reminiscent of the ‘operators’ in The Matrix, but this technology may soon stray from the realm of science-fiction into that of science-fact. Kendrick Kay and colleagues from the University of California, Berkeley have created a decoder that can accurately work out the one image from a large set that an observer is looking at, based solely on a scan of their brain activity.
The machine is still a while away from being a full-blown brain-reader. Rather than reconstructing what the onlooker is viewing from scratch, it can only select the most likely fit from a set of possible images. Even so, it’s no small feat, especially since the set of possible pictures is both very large and completely new to the viewer. And while previous similar studies used very simple images like gratings, Kay’s decoder has the ability to recognise actual photos.

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