Can fMRI Read your Mind ? |
| Written by Laurent Hermoye, PhD | |
| Thursday, 07 May 2009 | |
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Who has never dreamt reading his wife's, his boss's or his future conquest's mind ? Will new brain imaging techniques replace diviners and other fortune-tellers ?
Several group have taken up this challenge, using artificial intelligence techniques to infer subjects' thoughts or actions from patterns of pixels activated in fMRI images. For example: the hippocampus is known to process experience into memories and to be involved in the recall of spatial locations. With stimuli generated by a virtual reality system, Hassabis et al. asked subjects to virtually move between 8 locations within 2 rooms. Using a pattern classification algorithm to analyse the fMRI results, they were able to guess at which location the subjects were standing at a given moment from the pattern of activation of specific voxels in their hippocampus and parahippocampal gyrus. Haynes et al. used similar pattern classification algorithms to predict the subject's intention to perform either an addition or a subtraction of two numbers he was shown. Decoding the activity in the anterior medial prefrontal cortex they were able to predict the subject's intention with 71% accuracy, so significatively above chance level. Kay et al. used receptive-field models to build a visual decoder from fMRI data. In the algorithm training step, they established how the activity of each voxel in the visual cortex responded to locations, orientations and spatial frequencies presented in 1750 images. In the image identification step, they presented images out of a set which was not used during the training session. By measuring the response of each voxel to the novel image and comparing it with the predicted response for each image out of this new set, they were able to guess which image was actually seen by the subject. So out of 1000 images (for example bird 1, bird 2, bird 3,..., dog 1, dog 2, dog 3,...,etc.), fMRI can guess which one you are seeing (for example dog 2). The next (but far more complex) step would be to reconstruct the image you are seeing or thinking about from scratch. Imagine a monster and ask the machine to draw a picture of it. The 3 experiments described here above are a first step towards mind reading. But, in spite of their experimental complexity, their scenarios remain relatively simple: it's a matter of guessing what you are seeing, doing or planifying within a pre-defined set of possibilities. But the number of thoughts is infinite. So, the mind reading experiment in a broader context would be much more complex. In addition, all these experiments are based on a direct relationship between a feature of the stimulus (for example the locations, frequencies and orientations in an image) and a neuroanatomical location. Whereas this relationship is clear for some functions (somatotopy, rétinotopy, tonotopy), it is more than uncertain for other. To conclude, functional MRI is a promising tool for, one day, reading in your mind. The possible applications go beyond the imaginable: unconscious thoughts reading, mind reading in patient with altered state of consciousness, lie detector,... But this kind of tool, which deals with the deepest of ourselves, must be manipulated with care and ethics... Version française: L'IRM fonctionnelle peut-elle lire dans vos pensées ? |
When you are thinking about something (let's say a bird), 
