Monday, October 11, 1999 Published at 19:10 GMT 20:10 UK
Looking through cats' eyes
Fuzzy but recognisable
By BBC News Online Science Editor Dr David Whitehouse
These are the first pictures from an extraordinary experiment which has probed what it is like to look through the eyes of another creature.
As reported on BBC News Online last week, a team of US scientists have wired a computer to a cat's brain and created videos of what the animal was seeing.
By recording the electrical activity of nerve cells in the thalamus, a region of the brain that receives signals from the eyes, researchers from the University of California at Berkeley were able to view these shapes.
The team used what they describe as a "linear decoding technique" to convert the signals from the stimulated cells into visual images.
Dr Yang Dan, Assistant Professor of Neurobiology at UC Berkeley, Fei Li and Garrett Stanley, now Assistant Professor of Biomedical Engineering at Harvard University conducted 11 experiments.
They recorded the output from 177 brain cells that responded to light and dark in the cat's field of view.
In total, the 177 cells were sensitive to a field of view of 6.4 by 6.4 degrees. As the brain cells were stimulated, an image of what the cat saw was reconstructed.
The first example is a face. Although the reconstructed image is rather fuzzy, it is clearly recognisable as a version of the original scene. It is possible that a clearer image could be obtained by sampling the electrical output of more cells.
In the cat's brain, as in ours, the signals from the thalamus cells undergo considerable signal processing in the higher regions of the brain that improve the quality of the image that is perceived.
Taking an image from a region of the brain before this image enhancement has taken place will result in a poorer image than the cat is able to see.
The other two examples show two woodland scenes, with tree trunks being the most prominent objects.
By being able to tap directly into the brain and extract a visual image the researchers have produced a "brain interface" that may one day allow the control of artificial organs and indeed machines by thought alone. It is also conceivable that, given time, it will be possible to record what one person sees and "play it back" to someone else either as it is happening or at a later date.