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Progress has been amazing in technologies to peek inside the living brain to observe its inner working. Yet we are still far from really following what is going on and in particular to relate the firing of neurones to specific stimuli. There is so much going on in our brain (in any brain actually) at any given time that singling out one activity from the many looks like an impossible task, particularly noticing that two activities (several) can share the firing of neurones.
The work on the Connectome is providing a very detailed map of connections among neurones but also this is not helping in pinpointing the neural circuits that are involved in an activity, like processing a word.
Can you think of something without, at least partly, visualising it and “voicing it” in your mind? Unlikely. Yet it is clear that vision is quite separate from wording, yet the two are connected with one another.
Now researchers at UC Berkeley have managed to identify (not pinpoint to the level of a single neurone) the areas that get involved when you think of a word and how your “thought” progressed in your brain subsequently activating different areas (watch the clip).
To capture and isolate the electrical activity minimising the noise generated by other activities the researchers have enrolled patients undergoing brain surgery to relieve them from epileptic symptoms. During the operation (brain surgery is normally done with the patient awake and interacting) they have used electrocorticography, the placement of electrodes directly on the brain, to pick up electrical activity from the various zones.
As it would be expected the visual and auditory cortex are the first to be activated (since they were receiving stimuli from the eyes and the ears) but then the prefrontal cortex takes over. It seems like the prefrontal cortex is the starting point of our thinking. It processes the data provided by our senses and makes sense out of them. Then it coordinates the response by activating the motor cortex. The placement of the electrodes didn’t allow the researchers to track the involvement of the memory but it is most likely that this was also activated by the prefrontal cortex.
Interestingly, the tracking has shown that the motor cortex gets activated even before the prefrontal cortex completes the processing of the data, hence before it has decided how to react, just in case! This might explain why some people, some time, speak before they have actually metabolised what needs to be spoken…
It is the first time that researchers have been able to follow the “thinking” of a brain. A very tiny step, but even the longest voyage begins with a small step.
