fMRI: Reading your mind

The brain is the largest consumer of oxygenated blood in the human body. When neural activity increases in certain areas of the brain, during talking or pondering a problem for example, perfusion of those areas are hence increased. This change in blood supply can be detected by fMRI or functional magnetic resonance imaging thanks to two phenomena:

• the different signals of oxyhemoglobin and deoxyhemoglobin,
• and the increased local perfusion.

With the BOLD (blood oxygen level dependent) technique it is possible to map a patient’s brain before a risky surgery so that important areas such as Broca’s or Wernicke’s can be spared.

(Broca’s area activated in four patient’s. Source: Journal of Young Investigators.)

Just recently, in a research paper published in Nature, scientists at The University of California at Berkeley claim to have figured out a way to predict the image that their subject is looking at.

Their experiement consisted of two phases. In the first phase the subjects were asked to view 1750 images and their brain activity was monitored with fMRI. This means that every 4 seconds a MRI scan was obtained. During the second phase the subjects were shown 120 novel images, and the software, based on previous experience, “guessed” what image the subjects were looking at.

How accurate was the software? In some cases it was correct 9 out of 10 times. In others its performance was very low; about 0,8%. How can these results contribute to scientific development?

Our results suggest that it may soon be possible to reconstruct a picture of a person’s visual experience from measurements of brain activity alone. Imagine a general brain-reading device that could reconstruct a picture of a person’s visual experience at any moment in time.

So, in the near future it might be possible to decode and store dreams for further viewing with this technique. I can think of one practical use: that is to help people suffering from PTSD verbalize their traumatizing experiences.

Further reading:

• Nature News
• Nature milestones: fMRI
• Article from The Guardian
• Original paper from Nature, published online 5 March 2008 (subscription required)

– Andras