Let’s start with reading electrical signals from the brain. The classical approach for measuring electrical activity was to place a net of electrodes on a subject's scalp and record the signals from there. While this may be safe, the skull interferes with the signals making it difficult to get the fine detail from small brain areas which is needed for deciphering the processes of language production. The best way to get fine detail is through the penetration of the brain with electrodes as used by Kennedy et al. However, as discussed above, this carries a high level of risk. The halfway house is a method known as electrocorticography (ECoG) whereby the skull is opened up and a net of electrodes is placed over specific areas of the brain.
There is however a short cut to programming all these words for a speech synthesiser and measuring the electrical signals. Think of a word like “school”, which is made up of four distinct sounds. “S” “K” “OO” “L.” These sounds are four examples of the building blocks of language. In English there are about 44 of these distinct sounds, known as phonemes. The hope is to find the electrical signatures for these 44 sounds, either in Wernicke’s or Broca’s Area, then construct the intended word from the findings. This hope is based on work by Schalk et al. published earlier this year which used ECoG on the motor cortex and Wernicke’s Area and was able to detect the phonemes “oo,” “ah,” “eh,” and “ee.” These weren’t the only findings, as it was also discovered that when looking at the motor cortex there was little difference between spoken words and imagined words, whereas when looking at Wernicke’s Area there was a much larger signal seen when words were only imagined as opposed to spoken – giving tantalising evidence of the inner voice I mentioned earlier and suggesting that it may perhaps be generated in this area of the brain.