Neural basis of spatial navigation in the congenitally blind

FOR most of us, the ability to navigate our environment is largely dependent on the sense of vision. We use visual information to note the location of landmarks, and to identify and negotiate obstacles. These visual cues also enable us to keep track of our movements, by monitoring how our position changes relative to landmarks and, when possible, our starting point and final destination. All of this information is combined to generate a cognitive map of the surroundings, on which successful navigation of that environment later on depends.

Despite the importance of vision for navigation, congenitally blind people – those born blind – can still generate neural representations of space. Exactly how is unclear, but it is thought to be by using a combination of touch, hearing and smell, and some are even known to use echolocation. Spatial navigation in the congenitally blind is therefore thought to involve different brain networks than those engaged in sighted people. A team of Danish researchers  now report, however, that the mechanisms underlying spatial navigation in the blind are much the same as those in sighted people, due to the brain’s remarkable ability to reconfigure itself. 

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Optogenetic fMRI

OF all the techniques used by neuroscientists, none has captured the imagination of the general public more than functional magnetic resonance imaging (fMRI). The technique, which is also referred to as functional neuroimaging and, more commonly, “brain scanning”, enables us to peer into the human brain non-invasively, to observe its workings and correlate specific thought processes or stimuli to activity in particular regions. fMRI data affect the way in which people perceive scientific results: colourful images of the brain have persuasive power, making the accompanying data seem more credible.

Functional neuroimaging is used widely by researchers, too, with tens of thousands of research papers describing fMRI studies being published in the past decade. Yet, a big question mark has been hanging over the validity of the technique for over a year and, furthermore, the way in which fMRI data are interpreted has also been called into question. Using a novel combination of fMRI and a recently developed state-of-the-art technique called optogenetics, researchers now provide the first direct evidence that the fMRI signal is a valid measure of brain activity.

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