Neuroscientists from the University of California, Berkeley have successfully decoded brain activity into audible sounds. In a study that included 15 subjects, the researchers could understand the decoded words 80 to 90% of the time. This is effectively mind reading.

To listen in on the brain’s activity, the researchers placed up to 256 electrodes on the temporal lobe, the home of auditory processing in the brain. Words were then read out to the subjects, and the resultant electrical activity from the temporal lobe was recorded. The brain breaks down sounds into frequency bands (blocks of 10 hertz, say), and specific parts of the temporal lobe (cortical sites) are then tasked with processing that sound. By recording which of these cortical sites are active when words are heard, the scientists could then reconstruct the sounds using computer software. If you want to see this in action, Berkeley has published a short MOV video that you can download.

Now, there are two caveats here, one obvious, one less so. First, this is invasive mind reading: To get those 256 electrodes onto your temporal lobe, you have to have part of your skull removed. The only reason the Berkeley researchers could perform this study in the first place is because they piggybacked on a medical procedure: The current state-of-the-art for curing intractable seizures is to use electrodes to work out which bit of the brain is misfiring, and then to cut it out. It is unlikely that a non-invasive, scalp-borne brain-computer interface will be capable of performing the same mind-reading tricks.

Second, the scientists kind of cheated: They were listening to the auditory center, which interprets signals from the ear — they weren’t actually listening to thoughts. There is some research that indicates that imagined words and images trigger similar parts of the brain in similar ways, and the scientists posit that similar techniques could be used to really read minds, but I’ll believe it when I see it.

Those niggling concerns aside, though, the applications for bona fide mind reading are monumental. In the case of comatose and locked-in patients, or even mute people (like Stephen Hawking), mind reading could provide an invaluable communication channel. Beyond medicine and into education and entertainment, mind reading obviously leads us down a very interesting path. Video games that respond to thoughts; advertising that varies depending on your mood; cars that brake when you think brake, rather than push the peddle.

With great power comes great responsibility, however. While I’d be the first person in the line to get my brain wired up, I’d want to be damn sure that I retain complete control over who gets access to my thoughts. We also have to bear in mind other recent discoveries, like the prosthetic bionic eye. The bionic eye uses a very similar technique to encode digital signals into electrical activity that the brain understands. How far away are we from replacing our temporal lobe with a digital equivalent? Will that usher in enhanced, bionic hearing? If computers can replace our vision and auditory systems, what’s next?