Can They Read My Brain?

Neuroscience is making giant strides, and one does not have to be schizophrenic to wonder whether it will ever crack the safety box of our minds. Will there be a time, perhaps in the near future, where our innermost feelings and intimate memories will be laid bare for others to scroll through? I believe that the answer is a cautious no—at least for a while.

Brain imaging technologies are no doubt powerful. Over fifteen years ago, at the dawn of functional magnetic resonance imaging, I was already marveling at the fact that we could detect a single motor action: any time a person clicked a small button with the left or right hand, we could see the corresponding motor cortex being activated, and we could tell which hand the person had used with over 98% accuracy. We could also tell which language the scanned person spoke. In response to spoken sentences in French, English, Hindi or Japanese, brain activation would either invade a large swath of the left hemisphere, including Broca’s area, or stay within the confines of the auditory cortex—a sure sign that the person did or did not understand what was being said. Recently, we also managed to tell whether an adult or a child had learned to read a given script—simply by monitoring the activation of the “visual word form area”, a brain region that holds our knowledge of legal letter strings.

Whenever I lectured on this research, I insisted on the limitations of our methods. Action and language are macro-codes of the brain, I explained. They mobilize gigantic cortical networks that lay centimeters apart and are therefore easily resolved by our coarse brain imagers. Most of our fine-grained thoughts, however, are encrypted in a micro-code of sub-millimeter neuronal activity patterns. The neural configurations that distinguish my thought of a giraffe from my thought of an elephant are minuscule, unique to my brain, and intermingled within the same brain regions. Therefore, they would forever escape decoding, at least by non-invasive imaging methods.

In 2008, Tom Mitchell’s beautiful Science paper proved me partially wrong. His research showed that snapshots of state-of-the-art functional MRI contained a lot of information about specific thoughts. When a person thought of different words or pictures, the brain activity patterns they evoked differed so much that a machine-learning algorithm could tell them apart much better than would be expected by chance. Strikingly, many of these patterns were macroscopic, and they were even similar in different people’s brains. This is because, when we think of a word, we do not merely activate a small set of neurons in the temporal lobes that serves as an internal pointer to its meaning. The activation also spreads to distant sensory and motor cortices that encode each word’s concrete network of associations. In all of us, the verb “kick” activates the foot region of the motor cortex, “banana” evokes a smell and a color, and so on. These associations and their cortical patterns are so predictable that even new, untrained words can be identified by their brain signature.

via   Stanislas Dehaene, Neuroscientist


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